Merge branch 'eugenp:master' into master

.github/ISSUE_TEMPLATE/issue_report.md

@@ -5,7 +5,7 @@ title: '[ISSUE] '
 ---
 
 **Article and Module Links**
-A link to the affected article and the affected module. The link to the module is the one in the "over on GitHub" standard phrase.
+A link to the affected article and the affected module. You can find the link to the module in the Conclusion section in the "on Github" standard phase.
 
 **Describe the Issue**
 A clear and concise description of what the issue is.
@@ -30,9 +30,3 @@ If applicable, add screenshots to help explain your problem.
 
 **Additional Context**
 Add any other context about the issue here.
-
-Note that, unfortunately, we can only help with issues that are specifically and directly related to the article - not with your own, custom application.
-
-StackOverflow is a great place to ask more general questions.
-
-That's primarily because we get a large number of questions and - while we do try to go through as much as everything and help wherever we can, we can't really get back to all of them.

algorithms-modules/algorithms-miscellaneous-7/src/main/java/com/baeldung/algorithms/rotatearray/RotateArray.java

@@ -0,0 +1,102 @@
+package com.baeldung.algorithms.rotatearray;
+
+/**
+ *  To speed up the rotation, we narrow k rotations to the remainder of k divided by the array length, or k module the array length.
+ *  Therefore, a large rotation number will be translated into the relative smallest rotation.
+ *  All solutions replace the original array, although they might use an extra array to compute the rotation.
+ */
+public class RotateArray {
+
+    private RotateArray() {
+        throw new IllegalStateException("Rotate array algorithm utility methods class");
+    }
+
+    /**
+     *
+     * @param arr array to apply rotation to
+     * @param k number of rotations
+     */
+    public static void bruteForce(int[] arr, int k) {
+        checkInvalidInput(arr, k);
+
+        k %= arr.length;
+        int temp;
+        int previous;
+        for (int i = 0; i < k; i++) {
+            previous = arr[arr.length - 1];
+            for (int j = 0; j < arr.length; j++) {
+                temp = arr[j];
+                arr[j] = previous;
+                previous = temp;
+            }
+        }
+    }
+
+    /**
+     *
+     * @param arr array to apply rotation to
+     * @param k number of rotations
+     */
+    public static void withExtraArray(int[] arr, int k) {
+        checkInvalidInput(arr, k);
+
+        int[] extraArray = new int[arr.length];
+        for (int i = 0; i < arr.length; i++) {
+            extraArray[(i + k) % arr.length] = arr[i];
+        }
+        System.arraycopy(extraArray, 0, arr, 0, arr.length);
+    }
+
+    /**
+     *
+     * @param arr array to apply rotation to
+     * @param k number of rotations
+     */
+    public static void cyclicReplacement(int[] arr, int k) {
+        checkInvalidInput(arr, k);
+
+        k = k % arr.length;
+        int count = 0;
+        for (int start = 0; count < arr.length; start++) {
+            int current = start;
+            int prev = arr[start];
+            do {
+                int next = (current + k) % arr.length;
+                int temp = arr[next];
+                arr[next] = prev;
+                prev = temp;
+                current = next;
+                count++;
+            } while (start != current);
+        }
+    }
+
+    /**
+     *
+     * @param arr array to apply rotation to
+     * @param k number of rotations
+     */
+    public static void reverse(int[] arr, int k) {
+        checkInvalidInput(arr, k);
+
+        k %= arr.length;
+        reverse(arr, 0, arr.length - 1);
+        reverse(arr, 0, k - 1);
+        reverse(arr, k, arr.length - 1);
+    }
+
+    private static void reverse(int[] nums, int start, int end) {
+        while (start < end) {
+            int temp = nums[start];
+            nums[start] = nums[end];
+            nums[end] = temp;
+            start++;
+            end--;
+        }
+    }
+
+    private static void checkInvalidInput(int[] arr, int rotation) {
+        if (rotation < 1 || arr == null)
+            throw new IllegalArgumentException("Rotation must be greater than zero or array must be not null");
+    }
+}

algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/rotatearray/RotateArrayUnitTest.java

@@ -0,0 +1,124 @@
+package com.baeldung.algorithms.rotatearray;
+
+import static com.baeldung.algorithms.rotatearray.RotateArray.bruteForce;
+import static com.baeldung.algorithms.rotatearray.RotateArray.cyclicReplacement;
+import static com.baeldung.algorithms.rotatearray.RotateArray.reverse;
+import static com.baeldung.algorithms.rotatearray.RotateArray.withExtraArray;
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+class RotateArrayUnitTest {
+
+    private final int[] arr = { 1, 2, 3, 4, 5, 6 };
+    private final int rotationLtArrayLength = 1;
+    private final int rotationGtArrayLength = arr.length + 2;
+    private final int[] ltArrayLengthRotation = { 6, 1, 2, 3, 4, 5 };
+    private final int[] gtArrayLengthRotation = { 5, 6, 1, 2, 3, 4 };
+
+    @Test
+    void givenInputArray_whenNoRotationOrEmptyArray_thenThrowIllegalArgumentException() {
+        final int noRotation = 0;
+        final int someRotation = arr.length - 1;
+
+        assertThrows(IllegalArgumentException.class, () -> bruteForce(arr, noRotation));
+        assertThrows(IllegalArgumentException.class, () -> withExtraArray(arr, noRotation));
+        assertThrows(IllegalArgumentException.class, () -> cyclicReplacement(arr, noRotation));
+        assertThrows(IllegalArgumentException.class, () -> reverse(arr, noRotation));
+
+        assertThrows(IllegalArgumentException.class, () -> bruteForce(null, someRotation));
+        assertThrows(IllegalArgumentException.class, () -> withExtraArray(null, someRotation));
+        assertThrows(IllegalArgumentException.class, () -> cyclicReplacement(null, someRotation));
+        assertThrows(IllegalArgumentException.class, () -> reverse(null, someRotation));
+    }
+
+    @Test
+    void givenInputArray_whenUseBruteForceRotationLtArrayLength_thenRotateArrayOk() {
+
+        bruteForce(arr, rotationLtArrayLength);
+        assertArrayEquals(ltArrayLengthRotation, arr);
+    }
+
+    @Test
+    void givenInputArray_whenUseBruteForceRotationGtArrayLength_thenRotateArrayOk() {
+
+        bruteForce(arr, rotationGtArrayLength);
+        assertArrayEquals(gtArrayLengthRotation, arr);
+    }
+
+    @Test
+    void givenInputArray_whenUseBruteForceRotationEqArrayLength_thenDoNothing() {
+        int[] expected = arr.clone();
+
+        bruteForce(arr, arr.length);
+        assertArrayEquals(expected, arr);
+    }
+
+    @Test
+    void givenInputArray_whenUseExtraArrayRotationLtArrayLength_thenRotateArrayOk() {
+
+        withExtraArray(arr, rotationLtArrayLength);
+        assertArrayEquals(ltArrayLengthRotation, arr);
+    }
+
+    @Test
+    void givenInputArray_whenUseExtraArrayRotationGtArrayLength_thenRotateArrayOk() {
+
+        withExtraArray(arr, rotationGtArrayLength);
+        assertArrayEquals(gtArrayLengthRotation, arr);
+    }
+
+    @Test
+    void givenInputArray_whenUseExtraArrayWithRotationEqArrayLength_thenDoNothing() {
+        int[] clone = arr.clone();
+
+        withExtraArray(arr, arr.length);
+        assertArrayEquals(clone, arr);
+    }
+
+    @Test
+    void givenInputArray_whenUseCyclicReplacementRotationLtArrayLength_thenRotateArrayOk() {
+
+        cyclicReplacement(arr, rotationLtArrayLength);
+        assertArrayEquals(ltArrayLengthRotation, arr);
+    }
+
+    @Test
+    void givenInputArray_whenUseCyclicReplacementRotationGtArrayLength_thenRotateArrayOk() {
+
+        cyclicReplacement(arr, rotationGtArrayLength);
+        assertArrayEquals(gtArrayLengthRotation, arr);
+    }
+
+    @Test
+    void givenInputArray_whenUseCyclicReplacementRotationEqArrayLength_thenDoNothing() {
+        int[] clone = arr.clone();
+
+        cyclicReplacement(arr, arr.length);
+        assertArrayEquals(clone, arr);
+    }
+
+    @Test
+    void givenInputArray_whenUseReverseRotationLtArrayLength_thenRotateArrayOk() {
+
+        reverse(arr, rotationLtArrayLength);
+        assertArrayEquals(ltArrayLengthRotation, arr);
+    }
+
+    @Test
+    void givenInputArray_whenUseReverseRotationGtArrayLength_thenRotateArrayOk() {
+
+        reverse(arr, rotationGtArrayLength);
+        assertArrayEquals(gtArrayLengthRotation, arr);
+    }
+
+    @Test
+    void givenInputArray_whenUseReverseRotationEqArrayLength_thenDoNothing() {
+
+        int[] clone = arr.clone();
+
+        reverse(arr, arr.length);
+        assertArrayEquals(clone, arr);
+    }
+}

apache-kafka-2/README.md

@@ -13,3 +13,4 @@ You can build the project from the command line using: *mvn clean install*, or i
 - [Read Data From the Beginning Using Kafka Consumer API](https://www.baeldung.com/java-kafka-consumer-api-read)
 - [Get Partition Count for a Topic in Kafka](https://www.baeldung.com/java-kafka-partition-count-topic)
 - [bootstrap-server in Kafka Configuration](https://www.baeldung.com/java-kafka-bootstrap-server)
+- [Introduction to Apache Kafka](https://www.baeldung.com/apache-kafka)

apache-kafka-2/src/test/java/com/baeldung/kafka/multipletopics/MultipleTopicsLiveTest.java

@@ -0,0 +1,103 @@
+package com.baeldung.kafka.multipletopics;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.Properties;
+import java.util.concurrent.ExecutionException;
+
+import org.apache.kafka.clients.consumer.ConsumerConfig;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.clients.consumer.KafkaConsumer;
+import org.apache.kafka.clients.producer.KafkaProducer;
+import org.apache.kafka.clients.producer.ProducerConfig;
+import org.apache.kafka.clients.producer.ProducerRecord;
+import org.apache.kafka.common.serialization.StringDeserializer;
+import org.apache.kafka.common.serialization.StringSerializer;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.testcontainers.containers.KafkaContainer;
+import org.testcontainers.junit.jupiter.Container;
+import org.testcontainers.junit.jupiter.Testcontainers;
+import org.testcontainers.utility.DockerImageName;
+
+// This live test needs a Docker Daemon running so that a kafka container can be created
+
+@Testcontainers
+public class MultipleTopicsLiveTest {
+
+    private final Logger log = LoggerFactory.getLogger(MultipleTopicsLiveTest.class);
+
+    private static final String CARD_PAYMENTS_TOPIC = "card-payments";
+    private static final String BANK_TRANSFERS_TOPIC = "bank-transfers";
+    private static KafkaProducer<String, String> producer;
+    private static KafkaConsumer<String, String> consumer;
+
+    @Container
+    private static final KafkaContainer KAFKA_CONTAINER = new KafkaContainer(DockerImageName.parse("confluentinc/cp-kafka:latest"));
+
+    @BeforeAll
+    static void setup() {
+        KAFKA_CONTAINER.addExposedPort(9092);
+        producer = new KafkaProducer<>(getProducerProperties());
+        consumer = new KafkaConsumer<>(getConsumerProperties());
+    }
+
+    @AfterAll
+    static void destroy() {
+        KAFKA_CONTAINER.stop();
+    }
+
+    private static Properties getProducerProperties() {
+        Properties producerProperties = new Properties();
+        producerProperties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, KAFKA_CONTAINER.getBootstrapServers());
+        producerProperties.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
+        producerProperties.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
+        return producerProperties;
+    }
+
+    private static Properties getConsumerProperties() {
+        Properties consumerProperties = new Properties();
+        consumerProperties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, KAFKA_CONTAINER.getBootstrapServers());
+        consumerProperties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
+        consumerProperties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
+        consumerProperties.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
+        consumerProperties.put(ConsumerConfig.GROUP_ID_CONFIG, "payments");
+        return consumerProperties;
+    }
+
+    @Test
+    void whenSendingMessagesOnTwoTopics_thenConsumerReceivesMessages() throws Exception {
+        publishMessages();
+
+        consumer.subscribe(Arrays.asList(CARD_PAYMENTS_TOPIC, BANK_TRANSFERS_TOPIC));
+
+        int eventsProcessed = 0;
+        for (ConsumerRecord<String, String> record : consumer.poll(Duration.ofSeconds(10))) {
+            log.info("Event on topic={}, payload={}", record.topic(), record.value());
+            eventsProcessed++;
+        }
+
+        assertThat(eventsProcessed).isEqualTo(2);
+    }
+
+    private void publishMessages() throws ExecutionException, InterruptedException {
+        ProducerRecord<String, String> cardPayment = new ProducerRecord<>(CARD_PAYMENTS_TOPIC, createCardPayment());
+        producer.send(cardPayment).get();
+
+        ProducerRecord<String, String> bankTransfer = new ProducerRecord<>(BANK_TRANSFERS_TOPIC, createBankTransfer());
+        producer.send(bankTransfer).get();
+    }
+
+    private String createCardPayment() {
+        return "{\"paymentReference\":\"A184028KM0013790\", \"type\":\"card\", \"amount\":\"275\", \"currency\":\"GBP\"}";
+    }
+
+    private String createBankTransfer() {
+        return "{\"paymentReference\":\"19ae2-18mk73-009\", \"type\":\"bank\", \"amount\":\"150\", \"currency\":\"EUR\"}";
+    }
+}

apache-poi-3/README.md

@@ -0,0 +1,3 @@
+## Relevant Articles
+- [How To Convert Excel Data Into List Of Java Objects](https://www.baeldung.com/java-convert-excel-data-into-list)
+- [Expand Columns with Apache POI](https://www.baeldung.com/java-apache-poi-expand-columns)

aws-modules/aws-dynamodb/.gitignore

@@ -0,0 +1,2 @@
+/target/
+.idea/

aws-modules/aws-dynamodb/README.md

@@ -0,0 +1,7 @@
+## AWS DYNAMODB
+
+This module contains articles about AWS DynamoDB
+
+### Relevant articles
+- [Integration Testing with a Local DynamoDB Instance](https://www.baeldung.com/dynamodb-local-integration-tests)
+

aws-modules/aws-dynamodb/pom.xml

@@ -0,0 +1,87 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>aws-dynamodb</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>aws-dynamodb</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>aws-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.amazonaws</groupId>
+            <artifactId>aws-java-sdk</artifactId>
+            <version>${aws-java-sdk.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.amazonaws</groupId>
+            <artifactId>DynamoDBLocal</artifactId>
+            <version>${dynamodblocal.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>commons-io</groupId>
+            <artifactId>commons-io</artifactId>
+            <version>${commons-io.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.google.code.gson</groupId>
+            <artifactId>gson</artifactId>
+            <version>${gson.version}</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-shade-plugin</artifactId>
+                <version>${maven-shade-plugin.version}</version>
+                <configuration>
+                    <createDependencyReducedPom>false</createDependencyReducedPom>
+                </configuration>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>shade</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <version>${maven-plugins-version}</version>
+                <executions>
+                    <execution>
+                        <id>copy</id>
+                        <phase>compile</phase>
+                        <goals>
+                            <goal>copy-dependencies</goal>
+                        </goals>
+                        <configuration>
+                            <includeScope></includeScope>
+                            <includeTypes>so,dll,dylib</includeTypes>
+                            <outputDirectory>native-libs</outputDirectory>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <gson.version>2.8.0</gson.version>
+        <dynamodblocal.version>1.21.1</dynamodblocal.version>
+        <maven-plugins-version>3.1.1</maven-plugins-version>
+    </properties>
+
+</project>

aws-modules/aws-dynamodb/src/test/java/com/baeldung/dynamodb/ProductInfoRepositoryIntegrationTest.java

@@ -49,10 +49,10 @@ public class ProductInfoRepositoryIntegrationTest {
     @BeforeClass
     public static void setupClass() {
         Properties testProperties = loadFromFileInClasspath("test.properties")
-                .filter(properties -> !isEmpty(properties.getProperty(AWS_ACCESSKEY)))
+            .filter(properties -> !isEmpty(properties.getProperty(AWS_ACCESSKEY)))
-                .filter(properties -> !isEmpty(properties.getProperty(AWS_SECRETKEY)))
+            .filter(properties -> !isEmpty(properties.getProperty(AWS_SECRETKEY)))
-                .filter(properties -> !isEmpty(properties.getProperty(DYNAMODB_ENDPOINT)))
+            .filter(properties -> !isEmpty(properties.getProperty(DYNAMODB_ENDPOINT)))
-                .orElseThrow(() -> new RuntimeException("Unable to get all of the required test property values"));
+            .orElseThrow(() -> new RuntimeException("Unable to get all of the required test property values"));
 
         String amazonAWSAccessKey = testProperties.getProperty(AWS_ACCESSKEY);
         String amazonAWSSecretKey = testProperties.getProperty(AWS_SECRETKEY);

aws-modules/aws-miscellaneous/pom.xml

@@ -16,31 +16,9 @@
 
     <dependencies>
         <dependency>
-            <groupId>com.amazonaws</groupId>
+            <groupId>software.amazon.awssdk</groupId>
-            <artifactId>aws-java-sdk</artifactId>
+            <artifactId>aws-sdk-java</artifactId>
-            <version>${aws-java-sdk.version}</version>
+            <version>${aws-java-sdk-v2.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.amazonaws</groupId>
-            <artifactId>aws-lambda-java-core</artifactId>
-            <version>${aws-lambda-java-core.version}</version>
-            <exclusions>
-                <exclusion>
-                    <artifactId>commons-logging</artifactId>
-                    <groupId>commons-logging</groupId>
-                </exclusion>
-            </exclusions>
-        </dependency>
-        <dependency>
-            <groupId>com.amazonaws</groupId>
-            <artifactId>aws-lambda-java-events</artifactId>
-            <version>${aws-lambda-java-events.version}</version>
-            <exclusions>
-                <exclusion>
-                    <artifactId>commons-logging</artifactId>
-                    <groupId>commons-logging</groupId>
-                </exclusion>
-            </exclusions>
         </dependency>
         <dependency>
             <groupId>commons-io</groupId>
@@ -52,12 +30,6 @@
             <artifactId>gson</artifactId>
             <version>${gson.version}</version>
         </dependency>
-        <dependency>
-            <groupId>com.amazonaws</groupId>
-            <artifactId>DynamoDBLocal</artifactId>
-            <version>${dynamodblocal.version}</version>
-            <scope>test</scope>
-        </dependency>
     </dependencies>
 
     <build>
@@ -101,8 +73,6 @@
     </build>
 
     <properties>
-        <aws-lambda-java-events.version>1.3.0</aws-lambda-java-events.version>
-        <aws-lambda-java-core.version>1.1.0</aws-lambda-java-core.version>
         <gson.version>2.8.0</gson.version>
         <dynamodblocal.version>1.21.1</dynamodblocal.version>
         <commons-codec-version>1.10.L001</commons-codec-version>

aws-modules/aws-miscellaneous/src/main/java/com/baeldung/ec2/EC2Application.java

@@ -2,136 +2,148 @@ package com.baeldung.ec2;
 
 import java.util.Arrays;
 
-import com.amazonaws.auth.AWSCredentials;
+import software.amazon.awssdk.auth.credentials.ProfileCredentialsProvider;
-import com.amazonaws.auth.AWSStaticCredentialsProvider;
+import software.amazon.awssdk.regions.Region;
-import com.amazonaws.auth.BasicAWSCredentials;
+import software.amazon.awssdk.services.ec2.Ec2Client;
-import com.amazonaws.regions.Regions;
+import software.amazon.awssdk.services.ec2.model.AuthorizeSecurityGroupIngressRequest;
-import com.amazonaws.services.ec2.AmazonEC2;
+import software.amazon.awssdk.services.ec2.model.CreateKeyPairRequest;
-import com.amazonaws.services.ec2.AmazonEC2ClientBuilder;
+import software.amazon.awssdk.services.ec2.model.CreateKeyPairResponse;
-import com.amazonaws.services.ec2.model.AuthorizeSecurityGroupIngressRequest;
+import software.amazon.awssdk.services.ec2.model.CreateSecurityGroupRequest;
-import com.amazonaws.services.ec2.model.CreateKeyPairRequest;
+import software.amazon.awssdk.services.ec2.model.DescribeInstancesRequest;
-import com.amazonaws.services.ec2.model.CreateKeyPairResult;
+import software.amazon.awssdk.services.ec2.model.DescribeInstancesResponse;
-import com.amazonaws.services.ec2.model.CreateSecurityGroupRequest;
+import software.amazon.awssdk.services.ec2.model.DescribeKeyPairsRequest;
-import com.amazonaws.services.ec2.model.DescribeInstancesRequest;
+import software.amazon.awssdk.services.ec2.model.DescribeKeyPairsResponse;
-import com.amazonaws.services.ec2.model.DescribeInstancesResult;
+import software.amazon.awssdk.services.ec2.model.IpPermission;
-import com.amazonaws.services.ec2.model.DescribeKeyPairsRequest;
+import software.amazon.awssdk.services.ec2.model.IpRange;
-import com.amazonaws.services.ec2.model.DescribeKeyPairsResult;
+import software.amazon.awssdk.services.ec2.model.MonitorInstancesRequest;
-import com.amazonaws.services.ec2.model.IpPermission;
+import software.amazon.awssdk.services.ec2.model.RebootInstancesRequest;
-import com.amazonaws.services.ec2.model.IpRange;
+import software.amazon.awssdk.services.ec2.model.RunInstancesRequest;
-import com.amazonaws.services.ec2.model.MonitorInstancesRequest;
+import software.amazon.awssdk.services.ec2.model.RunInstancesResponse;
-import com.amazonaws.services.ec2.model.RebootInstancesRequest;
+import software.amazon.awssdk.services.ec2.model.StartInstancesRequest;
-import com.amazonaws.services.ec2.model.RunInstancesRequest;
+import software.amazon.awssdk.services.ec2.model.StartInstancesResponse;
-import com.amazonaws.services.ec2.model.StartInstancesRequest;
+import software.amazon.awssdk.services.ec2.model.StopInstancesRequest;
-import com.amazonaws.services.ec2.model.StopInstancesRequest;
+import software.amazon.awssdk.services.ec2.model.UnmonitorInstancesRequest;
-import com.amazonaws.services.ec2.model.UnmonitorInstancesRequest;
 
 public class EC2Application {
 
-    private static final AWSCredentials credentials;
-
-    static {
-        // put your accesskey and secretkey here
-        credentials = new BasicAWSCredentials(
-            "<AWS accesskey>", 
-            "<AWS secretkey>"
-        );
-    }
-
     public static void main(String[] args) {
        
         // Set up the client
-        AmazonEC2 ec2Client = AmazonEC2ClientBuilder.standard()
+        Ec2Client ec2Client = Ec2Client.builder()
-            .withCredentials(new AWSStaticCredentialsProvider(credentials))
+            .credentialsProvider(ProfileCredentialsProvider.create("default"))
-            .withRegion(Regions.US_EAST_1)
+            .region(Region.US_EAST_1)
             .build();
 
         // Create a security group
-        CreateSecurityGroupRequest createSecurityGroupRequest = new CreateSecurityGroupRequest().withGroupName("BaeldungSecurityGroup")
+        CreateSecurityGroupRequest createSecurityGroupRequest = CreateSecurityGroupRequest.builder()
-            .withDescription("Baeldung Security Group");
+            .groupName("BaeldungSecurityGroup")
+            .description("Baeldung Security Group")
+            .build();
+
         ec2Client.createSecurityGroup(createSecurityGroupRequest);
 
         // Allow HTTP and SSH traffic
-        IpRange ipRange1 = new IpRange().withCidrIp("0.0.0.0/0");
+        IpRange ipRange1 = IpRange.builder()
+            .cidrIp("0.0.0.0/0")
+            .build();
 
-        IpPermission ipPermission1 = new IpPermission().withIpv4Ranges(Arrays.asList(new IpRange[] { ipRange1 }))
+        IpPermission ipPermission1 = IpPermission.builder()
-            .withIpProtocol("tcp")
+            .ipRanges(Arrays.asList(ipRange1))
-            .withFromPort(80)
+            .ipProtocol("tcp")
-            .withToPort(80);
+            .fromPort(80)
+            .toPort(80)
+            .build();
 
-        IpPermission ipPermission2 = new IpPermission().withIpv4Ranges(Arrays.asList(new IpRange[] { ipRange1 }))
+        IpPermission ipPermission2 = IpPermission.builder()
-            .withIpProtocol("tcp")
+            .ipRanges(Arrays.asList(ipRange1))
-            .withFromPort(22)
+            .ipProtocol("tcp")
-            .withToPort(22);
+            .fromPort(22)
+            .toPort(22)
+            .build();
 
-        AuthorizeSecurityGroupIngressRequest authorizeSecurityGroupIngressRequest = new AuthorizeSecurityGroupIngressRequest()
+        AuthorizeSecurityGroupIngressRequest authorizeSecurityGroupIngressRequest = AuthorizeSecurityGroupIngressRequest
-            .withGroupName("BaeldungSecurityGroup")
+            .builder()
-            .withIpPermissions(ipPermission1, ipPermission2);
+            .groupName("BaeldungSecurityGroup")
+            .ipPermissions(ipPermission1, ipPermission2)
+            .build();
 
         ec2Client.authorizeSecurityGroupIngress(authorizeSecurityGroupIngressRequest);
 
         // Create KeyPair
-        CreateKeyPairRequest createKeyPairRequest = new CreateKeyPairRequest()
+        CreateKeyPairRequest createKeyPairRequest = CreateKeyPairRequest.builder()
-            .withKeyName("baeldung-key-pair");
+            .keyName("baeldung-key-pair")
-        CreateKeyPairResult createKeyPairResult = ec2Client.createKeyPair(createKeyPairRequest);
+            .build();
-        String privateKey = createKeyPairResult
+
-            .getKeyPair()
+        CreateKeyPairResponse createKeyPairResponse = ec2Client.createKeyPair(createKeyPairRequest);
-            .getKeyMaterial(); // make sure you keep it, the private key, Amazon doesn't store the private key
+        String privateKey = createKeyPairResponse.keyMaterial();
+        // make sure you keep it, the private key, Amazon doesn't store the private key
 
         // See what key-pairs you've got
-        DescribeKeyPairsRequest describeKeyPairsRequest = new DescribeKeyPairsRequest();
+        DescribeKeyPairsRequest describeKeyPairsRequest = DescribeKeyPairsRequest.builder()
-        DescribeKeyPairsResult describeKeyPairsResult = ec2Client.describeKeyPairs(describeKeyPairsRequest);
+            .build();
+        DescribeKeyPairsResponse describeKeyPairsResponse = ec2Client.describeKeyPairs(describeKeyPairsRequest);
 
         // Launch an Amazon Instance
-        RunInstancesRequest runInstancesRequest = new RunInstancesRequest().withImageId("ami-97785bed") // https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/AMIs.html | https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/usingsharedamis-finding.html
+        RunInstancesRequest runInstancesRequest = RunInstancesRequest.builder()
-            .withInstanceType("t2.micro") // https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-types.html
+            .imageId("ami-97785bed")
-            .withMinCount(1)
+            .instanceType("t2.micro") // https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-types.html
-            .withMaxCount(1)
+            .minCount(1)
-            .withKeyName("baeldung-key-pair") // optional - if not present, can't connect to instance
+            .maxCount(1)
-            .withSecurityGroups("BaeldungSecurityGroup");
+            .keyName("baeldung-key-pair") // optional - if not present, can't connect to instance
+            .securityGroups("BaeldungSecurityGroup")
+            .build();
 
-        String yourInstanceId = ec2Client.runInstances(runInstancesRequest).getReservation().getInstances().get(0).getInstanceId();
+        RunInstancesResponse runInstancesResponse = ec2Client.runInstances(runInstancesRequest);
+        String yourInstanceId = runInstancesResponse.instances().get(0).instanceId();
 
         // Start an Instance
-        StartInstancesRequest startInstancesRequest = new StartInstancesRequest()
+        StartInstancesRequest startInstancesRequest = StartInstancesRequest.builder()
-            .withInstanceIds(yourInstanceId);
+            .instanceIds(yourInstanceId)
+            .build();
+
+        StartInstancesResponse startInstancesResponse = ec2Client.startInstances(startInstancesRequest);
 
-        ec2Client.startInstances(startInstancesRequest);
 
         // Monitor Instances
-        MonitorInstancesRequest monitorInstancesRequest = new MonitorInstancesRequest()
+        MonitorInstancesRequest monitorInstancesRequest = MonitorInstancesRequest.builder()
-            .withInstanceIds(yourInstanceId);
+            .instanceIds(yourInstanceId)
+            .build();
+
 
         ec2Client.monitorInstances(monitorInstancesRequest);
 
-        UnmonitorInstancesRequest unmonitorInstancesRequest = new UnmonitorInstancesRequest()
+        UnmonitorInstancesRequest unmonitorInstancesRequest = UnmonitorInstancesRequest.builder()
-            .withInstanceIds(yourInstanceId);
+            .instanceIds(yourInstanceId)
+            .build();
 
         ec2Client.unmonitorInstances(unmonitorInstancesRequest);
 
         // Reboot an Instance
-
+        RebootInstancesRequest rebootInstancesRequest = RebootInstancesRequest.builder()
-        RebootInstancesRequest rebootInstancesRequest = new RebootInstancesRequest()
+            .instanceIds(yourInstanceId)
-            .withInstanceIds(yourInstanceId);
+            .build();
 
         ec2Client.rebootInstances(rebootInstancesRequest);
 
         // Stop an Instance
-        StopInstancesRequest stopInstancesRequest = new StopInstancesRequest()
+        StopInstancesRequest stopInstancesRequest = StopInstancesRequest.builder()
-            .withInstanceIds(yourInstanceId);
+            .instanceIds(yourInstanceId)
+            .build();
+
 
         ec2Client.stopInstances(stopInstancesRequest)
-            .getStoppingInstances()
+            .stoppingInstances()
             .get(0)
-            .getPreviousState()
+            .previousState()
-            .getName();
+            .name();
 
         // Describe an Instance
-        DescribeInstancesRequest describeInstancesRequest = new DescribeInstancesRequest();
+        DescribeInstancesRequest describeInstancesRequest = DescribeInstancesRequest.builder().build();
-        DescribeInstancesResult response = ec2Client.describeInstances(describeInstancesRequest);
+        DescribeInstancesResponse response = ec2Client.describeInstances(describeInstancesRequest);
-        System.out.println(response.getReservations()
+        System.out.println(response.reservations()
             .get(0)
-            .getInstances()
+            .instances()
             .get(0)
-            .getKernelId());
+            .kernelId());
     }
 }

aws-modules/aws-miscellaneous/src/main/java/com/baeldung/rds/AWSRDSService.java

@@ -1,13 +1,5 @@
 package com.baeldung.rds;
 
-import com.amazonaws.auth.AWSCredentialsProvider;
-import com.amazonaws.auth.AWSStaticCredentialsProvider;
-import com.amazonaws.auth.BasicAWSCredentials;
-import com.amazonaws.regions.Regions;
-import com.amazonaws.services.rds.AmazonRDS;
-import com.amazonaws.services.rds.AmazonRDSClientBuilder;
-import com.amazonaws.services.rds.model.*;
-
 import java.io.IOException;
 import java.io.InputStream;
 import java.sql.*;
@@ -16,12 +8,22 @@ import java.util.Properties;
 import java.util.UUID;
 import java.util.logging.Logger;
 
+import software.amazon.awssdk.auth.credentials.ProfileCredentialsProvider;
+import software.amazon.awssdk.regions.Region;
+import software.amazon.awssdk.services.rds.RdsClient;
+import software.amazon.awssdk.services.rds.model.CreateDbInstanceRequest;
+import software.amazon.awssdk.services.rds.model.CreateDbInstanceResponse;
+import software.amazon.awssdk.services.rds.model.DBInstance;
+import software.amazon.awssdk.services.rds.model.DeleteDbInstanceRequest;
+import software.amazon.awssdk.services.rds.model.DeleteDbInstanceResponse;
+import software.amazon.awssdk.services.rds.model.DescribeDbInstancesResponse;
+import software.amazon.awssdk.services.rds.model.Endpoint;
+
 public class AWSRDSService {
 
 
     final static Logger logger = Logger.getLogger(AWSRDSService.class.getName());
-    private AWSCredentialsProvider credentials;
+    private RdsClient rdsClient;
-    private AmazonRDS amazonRDS;
     private String db_username;
     private String db_password;
     private String db_database;
@@ -34,22 +36,17 @@ public class AWSRDSService {
     * **/
     public AWSRDSService() throws IOException {
         //Init RDS client with credentials and region.
-        credentials = new
-                AWSStaticCredentialsProvider(new
-                BasicAWSCredentials("<ACCESS_KEY>",
-                "<SECRET_KEY>"));
-        amazonRDS = AmazonRDSClientBuilder.standard().withCredentials(credentials)
-                .withRegion(Regions.AP_SOUTHEAST_2).build();
         Properties prop = new Properties();
         InputStream input = AWSRDSService.class.getClassLoader().getResourceAsStream("db.properties");
         prop.load(input);
         db_username = prop.getProperty("db_username");
         db_password = prop.getProperty("db_password");
         db_database = prop.getProperty("db_database");
-    }
 
-    public AWSRDSService(AmazonRDS amazonRDS){
+        rdsClient = RdsClient.builder()
-        this.amazonRDS = amazonRDS;
+            .region(Region.AP_SOUTHEAST_2)
+            .credentialsProvider(ProfileCredentialsProvider.create("default"))
+            .build();
     }
 
     /**
@@ -60,29 +57,29 @@ public class AWSRDSService {
     public String launchInstance() {
 
         String identifier = "";
-        CreateDBInstanceRequest request = new CreateDBInstanceRequest();
+        CreateDbInstanceRequest instanceRequest = CreateDbInstanceRequest.builder()
-        // RDS instance name
+            .dbInstanceIdentifier("Sydney")
-        request.setDBInstanceIdentifier("Sydney");
+            .engine("postgres")
-        request.setEngine("postgres");
+            .multiAZ(false)
-        request.setMultiAZ(false);
+            .masterUsername(db_username)
-        request.setMasterUsername(db_username);
+            .masterUserPassword(db_password)
-        request.setMasterUserPassword(db_password);
+            .dbName(db_database)
-        request.setDBName(db_database);
+            .storageType("gp2")
-        request.setStorageType("gp2");
+            .allocatedStorage(10)
-        request.setAllocatedStorage(10);
+            .build();
 
-        DBInstance instance = amazonRDS.createDBInstance(request);
+        CreateDbInstanceResponse createDbInstanceResponse = rdsClient.createDBInstance(instanceRequest);
 
         // Information about the new RDS instance
-        identifier = instance.getDBInstanceIdentifier();
+        identifier = createDbInstanceResponse.dbInstance().dbInstanceIdentifier();
-        String status = instance.getDBInstanceStatus();
+        String status = createDbInstanceResponse.dbInstance().dbInstanceStatus();
-        Endpoint endpoint = instance.getEndpoint();
+        Endpoint endpoint = createDbInstanceResponse.dbInstance().endpoint();
-        String endpoint_url = "Endpoint URL not available yet.";
+        String endpointUrl = "Endpoint URL not available yet.";
         if (endpoint != null) {
-            endpoint_url = endpoint.toString();
+            endpointUrl = endpoint.toString();
         }
         logger.info(identifier + "\t" + status);
-        logger.info(endpoint_url);
+        logger.info(endpointUrl);
 
         return identifier;
 
@@ -90,44 +87,44 @@ public class AWSRDSService {
 
     // Describe DB instances
     public void listInstances() {
-        DescribeDBInstancesResult result = amazonRDS.describeDBInstances();
+        DescribeDbInstancesResponse response = rdsClient.describeDBInstances();
-        List<DBInstance> instances = result.getDBInstances();
+        List<DBInstance> instances = response.dbInstances();
         for (DBInstance instance : instances) {
             // Information about each RDS instance
-            String identifier = instance.getDBInstanceIdentifier();
+            String identifier = instance.dbInstanceIdentifier();
-            String engine = instance.getEngine();
+            String engine = instance.engine();
-            String status = instance.getDBInstanceStatus();
+            String status = instance.dbInstanceStatus();
-            Endpoint endpoint = instance.getEndpoint();
+            Endpoint endpoint = instance.endpoint();
-            String endpoint_url = "Endpoint URL not available yet.";
+            String endpointUrl = "Endpoint URL not available yet.";
             if (endpoint != null) {
-                endpoint_url = endpoint.toString();
+                endpointUrl = endpoint.toString();
             }
             logger.info(identifier + "\t" + engine + "\t" + status);
-            logger.info("\t" + endpoint_url);
+            logger.info("\t" + endpointUrl);
         }
-
     }
 
     //Delete RDS instance
     public void terminateInstance(String identifier) {
 
-        DeleteDBInstanceRequest request = new DeleteDBInstanceRequest();
+        DeleteDbInstanceRequest request = DeleteDbInstanceRequest.builder()
-        request.setDBInstanceIdentifier(identifier);
+            .dbInstanceIdentifier(identifier)
-        request.setSkipFinalSnapshot(true);
+            .skipFinalSnapshot(true)
+            .build();
 
         // Delete the RDS instance
-        DBInstance instance = amazonRDS.deleteDBInstance(request);
+        DeleteDbInstanceResponse response = rdsClient.deleteDBInstance(request);
 
         // Information about the RDS instance being deleted
-        String status = instance.getDBInstanceStatus();
+        String status = response.dbInstance().dbInstanceStatus();
-        Endpoint endpoint = instance.getEndpoint();
+        Endpoint endpoint = response.dbInstance().endpoint();
-        String endpoint_url = "Endpoint URL not available yet.";
+        String endpointUrl = "Endpoint URL not available yet.";
         if (endpoint != null) {
-            endpoint_url = endpoint.toString();
+            endpointUrl = endpoint.toString();
         }
 
         logger.info(identifier + "\t" + status);
-        logger.info(endpoint_url);
+        logger.info(endpointUrl);
 
     }
 

aws-modules/aws-miscellaneous/src/main/java/com/baeldung/sqs/SQSApplication.java

@@ -5,140 +5,190 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
-import com.amazonaws.auth.AWSCredentials;
+import software.amazon.awssdk.auth.credentials.ProfileCredentialsProvider;
-import com.amazonaws.auth.AWSStaticCredentialsProvider;
+import software.amazon.awssdk.regions.Region;
-import com.amazonaws.auth.BasicAWSCredentials;
+import software.amazon.awssdk.services.sqs.SqsClient;
-import com.amazonaws.regions.Regions;
+import software.amazon.awssdk.services.sqs.model.CreateQueueRequest;
-import com.amazonaws.services.sqs.AmazonSQSClientBuilder;
+import software.amazon.awssdk.services.sqs.model.DeleteMessageRequest;
-import com.amazonaws.services.sqs.model.CreateQueueRequest;
+import software.amazon.awssdk.services.sqs.model.GetQueueAttributesRequest;
-import com.amazonaws.services.sqs.model.DeleteMessageRequest;
+import software.amazon.awssdk.services.sqs.model.GetQueueAttributesResponse;
-import com.amazonaws.services.sqs.model.GetQueueAttributesRequest;
+import software.amazon.awssdk.services.sqs.model.GetQueueUrlRequest;
-import com.amazonaws.services.sqs.model.GetQueueAttributesResult;
+import software.amazon.awssdk.services.sqs.model.GetQueueUrlResponse;
-import com.amazonaws.services.sqs.model.MessageAttributeValue;
+import software.amazon.awssdk.services.sqs.model.Message;
-import com.amazonaws.services.sqs.model.ReceiveMessageRequest;
+import software.amazon.awssdk.services.sqs.model.MessageAttributeValue;
-import com.amazonaws.services.sqs.model.SendMessageBatchRequest;
+import software.amazon.awssdk.services.sqs.model.QueueAttributeName;
-import com.amazonaws.services.sqs.model.SendMessageRequest;
+import software.amazon.awssdk.services.sqs.model.ReceiveMessageRequest;
-import com.amazonaws.services.sqs.model.SetQueueAttributesRequest;
+import software.amazon.awssdk.services.sqs.model.SendMessageBatchRequest;
-import com.amazonaws.services.sqs.model.SendMessageBatchRequestEntry;
+import software.amazon.awssdk.services.sqs.model.SendMessageBatchRequestEntry;
-import com.amazonaws.services.sqs.model.Message;
+import software.amazon.awssdk.services.sqs.model.SendMessageRequest;
-import com.amazonaws.services.sqs.AmazonSQS;
+import software.amazon.awssdk.services.sqs.model.SetQueueAttributesRequest;
 
 public class SQSApplication {
 
-    private static final AWSCredentials credentials;
+    private static final String STANDARD_QUEUE_NAME = "baeldung-queue";
-
+    private static final String FIFO_QUEUE_NAME = "baeldung-queue.fifo";
-    static {
+    private static final String DEAD_LETTER_QUEUE_NAME = "baeldung-dead-letter-queue";
-        // put your accesskey and secretkey here
-        credentials = new BasicAWSCredentials(
-            "<AWS accesskey>", 
-            "<AWS secretkey>"
-        );
-    }
 
     public static void main(String[] args) {
 
         // Set up the client
-        AmazonSQS sqs = AmazonSQSClientBuilder.standard()
+        SqsClient sqsClient = SqsClient.builder()
-            .withCredentials(new AWSStaticCredentialsProvider(credentials))
+            .region(Region.US_EAST_1)
-            .withRegion(Regions.US_EAST_1)
+            .credentialsProvider(ProfileCredentialsProvider.create())
             .build();
 
         // Create a standard queue
+        CreateQueueRequest createStandardQueueRequest = CreateQueueRequest.builder()
+            .queueName(STANDARD_QUEUE_NAME)
+            .build();
 
-        CreateQueueRequest createStandardQueueRequest = new CreateQueueRequest("baeldung-queue");
+        sqsClient.createQueue(createStandardQueueRequest);
-        String standardQueueUrl = sqs.createQueue(createStandardQueueRequest)
+
-            .getQueueUrl();
+        System.out.println("\nGet queue url");
+
+        GetQueueUrlResponse getQueueUrlResponse = sqsClient.getQueueUrl(GetQueueUrlRequest.builder()
+            .queueName(STANDARD_QUEUE_NAME)
+            .build());
+        String standardQueueUrl = getQueueUrlResponse.queueUrl();
 
         System.out.println(standardQueueUrl);
 
         // Create a fifo queue
+        Map<QueueAttributeName, String> queueAttributes = new HashMap<>();
+        queueAttributes.put(QueueAttributeName.FIFO_QUEUE, "true");
+        queueAttributes.put(QueueAttributeName.CONTENT_BASED_DEDUPLICATION, "true");
 
-        Map<String, String> queueAttributes = new HashMap<String, String>();
+        CreateQueueRequest createFifoQueueRequest = CreateQueueRequest.builder()
-        queueAttributes.put("FifoQueue", "true");
+            .queueName(FIFO_QUEUE_NAME)
-        queueAttributes.put("ContentBasedDeduplication", "true");
+            .attributes(queueAttributes)
+            .build();
 
-        CreateQueueRequest createFifoQueueRequest = new CreateQueueRequest("baeldung-queue.fifo").withAttributes(queueAttributes);
+        sqsClient.createQueue(createFifoQueueRequest);
-        String fifoQueueUrl = sqs.createQueue(createFifoQueueRequest)
+
-            .getQueueUrl();
+        GetQueueUrlResponse getFifoQueueUrlResponse = sqsClient.getQueueUrl(GetQueueUrlRequest.builder()
+            .queueName(FIFO_QUEUE_NAME)
+            .build());
+
+        String fifoQueueUrl = getFifoQueueUrlResponse.queueUrl();
 
         System.out.println(fifoQueueUrl);
 
         // Set up a dead letter queue
+        CreateQueueRequest createDeadLetterQueueRequest = CreateQueueRequest.builder()
+            .queueName(DEAD_LETTER_QUEUE_NAME)
+            .build();
 
-        String deadLetterQueueUrl = sqs.createQueue("baeldung-dead-letter-queue")
+        String deadLetterQueueUrl = sqsClient.createQueue(createDeadLetterQueueRequest)
-            .getQueueUrl();
+            .queueUrl();
 
-        GetQueueAttributesResult deadLetterQueueAttributes = sqs.getQueueAttributes(new GetQueueAttributesRequest(deadLetterQueueUrl).withAttributeNames("QueueArn"));
+        GetQueueAttributesRequest getQueueAttributesRequest = GetQueueAttributesRequest.builder()
+            .queueUrl(deadLetterQueueUrl)
+            .attributeNames(QueueAttributeName.QUEUE_ARN)
+            .build();
 
-        String deadLetterQueueARN = deadLetterQueueAttributes.getAttributes()
+        GetQueueAttributesResponse deadLetterQueueAttributes = sqsClient.getQueueAttributes(getQueueAttributesRequest);
+
+        String deadLetterQueueARN = deadLetterQueueAttributes.attributes()
             .get("QueueArn");
 
-        SetQueueAttributesRequest queueAttributesRequest = new SetQueueAttributesRequest().withQueueUrl(standardQueueUrl)
+        Map<QueueAttributeName, String> attributes = new HashMap<>();
-            .addAttributesEntry("RedrivePolicy", "{\"maxReceiveCount\":\"2\", " + "\"deadLetterTargetArn\":\"" + deadLetterQueueARN + "\"}");
+        attributes.put(QueueAttributeName.REDRIVE_POLICY, "{\"maxReceiveCount\":\"5\", \"deadLetterTargetArn\":\"" + deadLetterQueueARN + "\"}");
 
-        sqs.setQueueAttributes(queueAttributesRequest);
+        SetQueueAttributesRequest queueAttributesRequest = SetQueueAttributesRequest.builder()
+            .queueUrl(standardQueueUrl)
+            .attributes(attributes)
+            .build();
+
+        sqsClient.setQueueAttributes(queueAttributesRequest);
 
         // Send a message to a standard queue
 
         Map<String, MessageAttributeValue> messageAttributes = new HashMap<>();
+        MessageAttributeValue messageAttributeValue = MessageAttributeValue.builder()
+            .stringValue("This is an attribute")
+            .dataType("String")
+            .build();
 
-        messageAttributes.put("AttributeOne", new MessageAttributeValue().withStringValue("This is an attribute")
+        messageAttributes.put("AttributeOne", messageAttributeValue);
-            .withDataType("String"));
 
-        SendMessageRequest sendMessageStandardQueue = new SendMessageRequest().withQueueUrl(standardQueueUrl)
+        SendMessageRequest sendMessageStandardQueue = SendMessageRequest.builder()
-            .withMessageBody("A simple message.")
+            .queueUrl(standardQueueUrl)
-            .withDelaySeconds(30) // Message will arrive in the queue after 30 seconds. We can use this only in standard queues
+            .messageBody("A simple message.")
-            .withMessageAttributes(messageAttributes);
+            .delaySeconds(30) // Message will arrive in the queue after 30 seconds. We can use this only in standard queues
+            .messageAttributes(messageAttributes)
+            .build();
 
-        sqs.sendMessage(sendMessageStandardQueue);
+        sqsClient.sendMessage(sendMessageStandardQueue);
 
         // Send a message to a fifo queue
 
-        SendMessageRequest sendMessageFifoQueue = new SendMessageRequest().withQueueUrl(fifoQueueUrl)
+        SendMessageRequest sendMessageFifoQueue = SendMessageRequest.builder()
-            .withMessageBody("FIFO Queue")
+            .queueUrl(fifoQueueUrl)
-            .withMessageGroupId("baeldung-group-1")
+            .messageBody("FIFO Queue")
-            .withMessageAttributes(messageAttributes);
+            .messageGroupId("baeldung-group-1")
+            .messageAttributes(messageAttributes)
+            .build();
 
-        sqs.sendMessage(sendMessageFifoQueue);
+        sqsClient.sendMessage(sendMessageFifoQueue);
 
         // Send multiple messages
 
         List<SendMessageBatchRequestEntry> messageEntries = new ArrayList<>();
-        messageEntries.add(new SendMessageBatchRequestEntry().withId("id-1")
+        SendMessageBatchRequestEntry messageBatchRequestEntry1 = SendMessageBatchRequestEntry.builder()
-            .withMessageBody("batch-1")
+            .id("id-1")
-            .withMessageGroupId("baeldung-group-1"));
+            .messageBody("batch-1")
-        messageEntries.add(new SendMessageBatchRequestEntry().withId("id-2")
+            .messageGroupId("baeldung-group-1")
-            .withMessageBody("batch-2")
+            .build();
-            .withMessageGroupId("baeldung-group-1"));
 
-        SendMessageBatchRequest sendMessageBatchRequest = new SendMessageBatchRequest(fifoQueueUrl, messageEntries);
+        SendMessageBatchRequestEntry messageBatchRequestEntry2 = SendMessageBatchRequestEntry.builder()
-        sqs.sendMessageBatch(sendMessageBatchRequest);
+            .id("id-2")
+            .messageBody("batch-2")
+            .messageGroupId("baeldung-group-1")
+            .build();
+
+        messageEntries.add(messageBatchRequestEntry1);
+        messageEntries.add(messageBatchRequestEntry2);
+
+        SendMessageBatchRequest sendMessageBatchRequest = SendMessageBatchRequest.builder()
+            .queueUrl(fifoQueueUrl)
+            .entries(messageEntries)
+            .build();
+
+        sqsClient.sendMessageBatch(sendMessageBatchRequest);
 
         // Read a message from a queue
 
-        ReceiveMessageRequest receiveMessageRequest = new ReceiveMessageRequest(fifoQueueUrl).withWaitTimeSeconds(10) // Long polling;
+        ReceiveMessageRequest receiveMessageRequest = ReceiveMessageRequest.builder()
-            .withMaxNumberOfMessages(1); // Max is 10
+            .waitTimeSeconds(10)
+            .maxNumberOfMessages(10)
+            .build();
 
-        List<Message> sqsMessages = sqs.receiveMessage(receiveMessageRequest)
+        List<Message> sqsMessages = sqsClient.receiveMessage(receiveMessageRequest)
-            .getMessages();
+            .messages();
 
         sqsMessages.get(0)
-            .getAttributes();
+            .attributes();
         sqsMessages.get(0)
-            .getBody();
+            .body();
 
         // Delete a message from a queue
+        DeleteMessageRequest deleteMessageRequest = DeleteMessageRequest.builder()
+            .queueUrl(fifoQueueUrl)
+            .receiptHandle(sqsMessages.get(0)
+                .receiptHandle())
+            .build();
 
-        sqs.deleteMessage(new DeleteMessageRequest().withQueueUrl(fifoQueueUrl)
+        sqsClient.deleteMessage(deleteMessageRequest);
-            .withReceiptHandle(sqsMessages.get(0)
-                .getReceiptHandle()));
 
         // Monitoring
-        GetQueueAttributesRequest getQueueAttributesRequest = new GetQueueAttributesRequest(standardQueueUrl).withAttributeNames("All");
+        GetQueueAttributesRequest getQueueAttributesRequestForMonitoring = GetQueueAttributesRequest.builder()
-        GetQueueAttributesResult getQueueAttributesResult = sqs.getQueueAttributes(getQueueAttributesRequest);
+            .queueUrl(standardQueueUrl)
-        System.out.println(String.format("The number of messages on the queue: %s", getQueueAttributesResult.getAttributes()
+            .build();
+
+        GetQueueAttributesResponse attributesResponse = sqsClient.getQueueAttributes(getQueueAttributesRequestForMonitoring);
+        System.out.println(String.format("The number of messages on the queue: %s", attributesResponse.attributes()
             .get("ApproximateNumberOfMessages")));
-        System.out.println(String.format("The number of messages in flight: %s", getQueueAttributesResult.getAttributes()
+        System.out.println(String.format("The number of messages in flight: %s", attributesResponse.attributes()
             .get("ApproximateNumberOfMessagesNotVisible")));
 
     }

aws-modules/pom.xml

@@ -5,6 +5,14 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>aws-modules</artifactId>
     <name>aws-modules</name>
+    <dependencies>
+        <dependency>
+            <groupId>com.amazonaws</groupId>
+            <artifactId>aws-java-sdk-dynamodb</artifactId>
+            <version>1.12.523</version>
+            <scope>compile</scope>
+        </dependency>
+    </dependencies>
     <packaging>pom</packaging>
 
     <parent>
@@ -15,6 +23,7 @@
 
     <modules>
         <module>aws-app-sync</module>
+        <module>aws-dynamodb</module>
         <module>aws-lambda-modules</module>
         <module>aws-miscellaneous</module>
         <module>aws-reactive</module>
@@ -24,6 +33,7 @@
 
     <properties>
         <aws-java-sdk.version>1.12.331</aws-java-sdk.version>
+        <aws-java-sdk-v2.version>2.20.147</aws-java-sdk-v2.version>
         <maven-shade-plugin.version>3.0.0</maven-shade-plugin.version>
     </properties>
 

core-java-modules/core-java-16/README.md

@@ -5,3 +5,4 @@
 - [Collecting Stream Elements into a List in Java](https://www.baeldung.com/java-stream-to-list-collecting)
 - [New Features in Java 16](https://www.baeldung.com/java-16-new-features)
 - [Guide to Java 8 groupingBy Collector](https://www.baeldung.com/java-groupingby-collector)
+- [Value-Based Classes in Java](https://www.baeldung.com/java-value-based-classes)

core-java-modules/core-java-16/src/main/java/com/baeldung/value_based_class/Point.java

@@ -30,6 +30,11 @@ public final class Point {
         return new Point(x, y, z);
     }
 
+    @Override
+    public String toString() {
+        return "Point{" + "x=" + x + ", y=" + y + ", z=" + z + '}';
+    }
+
     @Override
     public boolean equals(Object other) {
         if (other == null || getClass() != other.getClass())

core-java-modules/core-java-16/src/test/java/com/baeldung/value_based_class/ValueBasedClassUnitTest.java

@@ -1,14 +1,17 @@
 package com.baeldung.value_based_class;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import org.junit.Assert;
 import org.junit.Test;
 
 public class ValueBasedClassUnitTest {
     @Test
     public void givenAutoboxedAndPrimitive_whenCompared_thenReturnEquals() {
-        int primitive_a = 125;
+        List<Integer> list = new ArrayList<>();
-        Integer obj_a = 125; // this is autoboxed
+        list.add(1); // this is autoboxed
-        Assert.assertSame(primitive_a, obj_a);
+        Assert.assertEquals(list.get(0), Integer.valueOf(1));
     }
 
     @Test

core-java-modules/core-java-17/src/test/java/com/baeldung/recordproperties/ReadRecordPropertiesByReflectionUnitTest.java

@@ -0,0 +1,89 @@
+package com.baeldung.recordproperties;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.RecordComponent;
+import java.util.ArrayList;
+
+import org.junit.jupiter.api.Test;
+
+record Player(String name, int age, Long score) {
+}
+
+public class ReadRecordPropertiesByReflectionUnitTest {
+    private static final Player ERIC = new Player("Eric", 28, 4242L);
+
+    @Test
+    void whenUsingRecordComponent_thenGetExpectedResult() {
+        var fields = new ArrayList<Field>();
+        RecordComponent[] components = Player.class.getRecordComponents();
+        for (var comp : components) {
+            try {
+                Field field = ERIC.getClass()
+                  .getDeclaredField(comp.getName());
+                field.setAccessible(true);
+                fields.add(field);
+            } catch (NoSuchFieldException e) {
+                // for simplicity, error handling is skipped
+            }
+        }
+
+        assertEquals(3, fields.size());
+
+        var nameField = fields.get(0);
+        var ageField = fields.get(1);
+        var scoreField = fields.get(2);
+        try {
+            assertEquals("name", nameField.getName());
+            assertEquals(String.class, nameField.getType());
+            assertEquals("Eric", nameField.get(ERIC));
+
+            assertEquals("age", ageField.getName());
+            assertEquals(int.class, ageField.getType());
+            assertEquals(28, ageField.get(ERIC));
+
+            assertEquals("score", scoreField.getName());
+            assertEquals(Long.class, scoreField.getType());
+            assertEquals(4242L, scoreField.get(ERIC));
+        } catch (IllegalAccessException exception) {
+            // for simplicity, error handling is skipped
+        }
+
+    }
+
+    @Test
+    void whenUsingClassGetDeclaredField_thenGetExpectedResult() {
+        // record has no public fields
+        assertEquals(0, Player.class.getFields().length);
+
+        var fields = new ArrayList<Field>();
+        for (var field : Player.class.getDeclaredFields()) {
+            field.setAccessible(true);
+            fields.add(field);
+        }
+
+        assertEquals(3, fields.size());
+        var nameField = fields.get(0);
+        var ageField = fields.get(1);
+        var scoreField = fields.get(2);
+
+        try {
+            assertEquals("name", nameField.getName());
+            assertEquals(String.class, nameField.getType());
+            assertEquals("Eric", nameField.get(ERIC));
+
+            assertEquals("age", ageField.getName());
+            assertEquals(int.class, ageField.getType());
+            assertEquals(28, ageField.get(ERIC));
+
+            assertEquals("score", scoreField.getName());
+            assertEquals(Long.class, scoreField.getType());
+            assertEquals(4242L, scoreField.get(ERIC));
+        } catch (IllegalAccessException ex) {
+            // for simplicity, error handling is skipped
+        }
+
+    }
+
+}

core-java-modules/core-java-18/pom.xml

@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-18</artifactId>
+    <name>core-java-18</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <release>${maven.compiler.release}</release>
+                    <compilerArgs>--enable-preview</compilerArgs>
+                    <source>${maven.compiler.source.version}</source>
+                    <target>${maven.compiler.target.version}</target>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>${surefire.plugin.version}</version>
+                <configuration>
+                    <forkCount>1</forkCount>
+                </configuration>
+                <dependencies>
+                    <dependency>
+                        <groupId>org.apache.maven.surefire</groupId>
+                        <artifactId>surefire-api</artifactId>
+                        <version>${surefire.plugin.version}</version>
+                    </dependency>
+                </dependencies>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <maven.compiler.source.version>18</maven.compiler.source.version>
+        <maven.compiler.target.version>18</maven.compiler.target.version>
+        <maven.compiler.release>18</maven.compiler.release>
+        <surefire.plugin.version>3.0.0-M5</surefire.plugin.version>
+    </properties>
+
+</project>

core-java-modules/core-java-18/src/main/java/com/baeldung/finalization_closeable_cleaner/FinalizationExamples.java

@@ -0,0 +1,27 @@
+package com.baeldung.finalization_closeable_cleaner;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+
+public class FinalizationExamples {
+    FileInputStream fis = null;
+
+    public void readFileOperationWithFinalization() throws IOException {
+        try {
+            fis = new FileInputStream("input.txt");
+            // perform operation on the file
+            System.out.println(fis.readAllBytes().length);
+
+        } finally {
+            if (fis != null)
+                fis.close();
+        }
+    }
+
+    public void readFileOperationWithTryWith() throws IOException {
+        try (FileInputStream fis = new FileInputStream("input.txt")) {
+            // perform operations
+            System.out.println(fis.readAllBytes().length);
+        }
+    }
+}

core-java-modules/core-java-18/src/main/java/com/baeldung/finalization_closeable_cleaner/MyCleanerResourceClass.java

@@ -0,0 +1,48 @@
+package com.baeldung.finalization_closeable_cleaner;
+
+import java.lang.ref.Cleaner;
+
+public class MyCleanerResourceClass implements AutoCloseable {
+    private static Resource resource;
+
+    private static final Cleaner cleaner = Cleaner.create();
+    private final Cleaner.Cleanable cleanable;
+
+    public MyCleanerResourceClass() {
+        resource = new Resource();
+        this.cleanable = cleaner.register(this, new CleaningState());
+    }
+
+    public void useResource() {
+        // using the resource here
+        resource.use();
+    }
+
+    @Override
+    public void close() {
+        // perform actions to close all underlying resources
+        this.cleanable.clean();
+    }
+
+    static class CleaningState implements Runnable {
+        CleaningState() {
+            // constructor
+        }
+
+        @Override
+        public void run() {
+            // some cleanup action
+            System.out.println("Cleanup done");
+        }
+    }
+
+    static class Resource {
+        void use() {
+            System.out.println("Using the resource");
+        }
+
+        void close() {
+            System.out.println("Cleanup done");
+        }
+    }
+}

core-java-modules/core-java-18/src/main/java/com/baeldung/finalization_closeable_cleaner/MyCloseableResourceClass.java

@@ -0,0 +1,25 @@
+package com.baeldung.finalization_closeable_cleaner;
+
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+
+public class MyCloseableResourceClass implements AutoCloseable {
+
+    private final FileInputStream fis;
+
+    public MyCloseableResourceClass() throws FileNotFoundException {
+        this.fis = new FileInputStream("src/main/resources/file.txt");
+
+    }
+
+    public int getByteLength() throws IOException {
+        System.out.println("Some operation");
+        return this.fis.readAllBytes().length;
+    }
+    @Override
+    public void close() throws IOException {
+        System.out.println("Finalized object");
+        this.fis.close();
+    }
+}

core-java-modules/core-java-18/src/main/java/com/baeldung/finalization_closeable_cleaner/MyFinalizableResourceClass.java

@@ -0,0 +1,24 @@
+package com.baeldung.finalization_closeable_cleaner;
+
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+
+public class MyFinalizableResourceClass {
+    private FileInputStream fis;
+
+    public MyFinalizableResourceClass() throws FileNotFoundException {
+        this.fis = new FileInputStream("src/main/resources/file.txt");
+    }
+
+    public int getByteLength() throws IOException {
+        System.out.println("Some operation");
+        return this.fis.readAllBytes().length;
+    }
+
+    @Override
+    protected void finalize() throws Throwable {
+        System.out.println("Finalized object");
+        this.fis.close();
+    }
+}

core-java-modules/core-java-18/src/main/resources/file.txt

@@ -0,0 +1 @@
+This is a test file.

core-java-modules/core-java-18/src/test/java/com/baeldung/finalization_closeable_cleaner/FinalizationCloseableCleanerUnitTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.finalization_closeable_cleaner;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+import java.io.IOException;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class FinalizationCloseableCleanerUnitTest {
+
+    @Test
+    public void givenMyFinalizationResource_whenUsingFinalize_thenShouldClean() {
+        assertDoesNotThrow(() -> {
+            MyFinalizableResourceClass mfr = new MyFinalizableResourceClass();
+            mfr.getByteLength();
+        });
+    }
+    @Test
+    public void givenMyCleanerResource_whenUsingCleanerAPI_thenShouldClean() {
+        assertDoesNotThrow(() -> {
+            try (MyCleanerResourceClass myCleanerResourceClass = new MyCleanerResourceClass()) {
+                myCleanerResourceClass.useResource();
+            }
+        });
+    }
+
+    @Test
+    public void givenCloseableResource_whenUsingTryWith_thenShouldClose() throws IOException {
+        int length = 0;
+        try (MyCloseableResourceClass mcr = new MyCloseableResourceClass()) {
+            length = mcr.getByteLength();
+        }
+        Assert.assertEquals(20, length);
+    }
+}

core-java-modules/core-java-21/README.md

@@ -1,2 +1,5 @@
 ## Relevant Articles
 - [Sequenced Collections in Java 21](https://www.baeldung.com/java-21-sequenced-collections)
+- [String Templates in Java 21](https://www.baeldung.com/java-21-string-templates)
+- [Unnamed Classes and Instance Main Methods in Java 21](https://www.baeldung.com/java-21-unnamed-class-instance-main)
+- [Unnamed Patterns and Variables in Java 21](https://www.baeldung.com/java-unnamed-patterns-variables)

core-java-modules/core-java-21/pom.xml

@@ -12,6 +12,12 @@
         <version>0.0.1-SNAPSHOT</version>
     </parent>
 
+    <properties>
+        <maven.compiler.source.version>21</maven.compiler.source.version>
+        <maven.compiler.target.version>21</maven.compiler.target.version>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
     <build>
         <plugins>
             <plugin>
@@ -20,14 +26,22 @@
                 <configuration>
                     <source>21</source>
                     <target>21</target>
-                    <compilerArgs>--enable-preview</compilerArgs>
+                    <!-- Needed due to a bug with JDK 21, described here: https://issues.apache.org/jira/browse/MCOMPILER-546?page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel&focusedCommentId=17767513 -->
+                    <debug>false</debug>
+                    <compilerArgs>
+                        <arg>--enable-preview</arg>
+                    </compilerArgs>
                 </configuration>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <configuration>
+                    <argLine>--enable-preview</argLine>
+                </configuration>
+            </plugin>
+
         </plugins>
     </build>
-    <properties>
+
-        <maven.compiler.source.version>21</maven.compiler.source.version>
-        <maven.compiler.target.version>21</maven.compiler.target.version>
-        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-    </properties>
 </project>

core-java-modules/core-java-21/src/main/java/com/baeldung/unnamed/variables/Car.java

@@ -0,0 +1,11 @@
+package com.baeldung.unnamed.variables;
+
+public record Car<T extends Engine>(String name, String color, T engine) { }
+
+abstract class Engine { }
+
+class GasEngine extends Engine { }
+
+class ElectricEngine extends Engine { }
+
+class HybridEngine extends Engine { }

core-java-modules/core-java-21/src/main/java/com/baeldung/unnamed/variables/UnnamedPatterns.java

@@ -0,0 +1,50 @@
+package com.baeldung.unnamed.variables;
+
+public class UnnamedPatterns {
+
+    static String getObjectsColorWithNamedPattern(Object object) {
+        if (object instanceof Car(String name, String color, Engine engine)) {
+            return color;
+        }
+        return "No color!";
+    }
+
+    static String getObjectsColorWithUnnamedPattern(Object object) {
+        if (object instanceof Car(_, String color, _)) {
+            return color;
+        }
+        return "No color!";
+    }
+
+    static String getObjectsColorWithSwitchAndNamedPattern(Object object) {
+        return switch (object) {
+            case Car(String name, String color, Engine engine) -> color;
+            default -> "No color!";
+        };
+    }
+
+    static String getObjectsColorWithSwitchAndUnnamedPattern(Object object) {
+        return switch (object) {
+            case Car(_, String color, _) -> color;
+            default -> "No color!";
+        };
+    }
+
+    static String getEngineTypeWithNamedPattern(Car<?> car) {
+        return switch (car) {
+            case Car(String name, String color, GasEngine engine) -> "gas";
+            case Car(String name, String color, ElectricEngine engine) -> "electric";
+            case Car(String name, String color, HybridEngine engine) -> "hybrid";
+            default -> "none";
+        };
+    }
+
+    static String getEngineTypeWithUnnamedPattern(Car<?> car) {
+        return switch (car) {
+            case Car(_, _, GasEngine _) -> "gas";
+            case Car(_, _, ElectricEngine _) -> "electric";
+            case Car(_, _, HybridEngine _) -> "hybrid";
+            default -> "none";
+        };
+    }
+}

core-java-modules/core-java-21/src/main/java/com/baeldung/unnamed/variables/UnnamedVariables.java

@@ -0,0 +1,134 @@
+package com.baeldung.unnamed.variables;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+
+class Transaction implements AutoCloseable {
+
+    @Override
+    public void close() {
+        System.out.println("Closed!");
+    }
+}
+
+public class UnnamedVariables {
+
+    static int countCarsOverLimitWithNamedVariable(Collection<Car<?>> cars, int limit) {
+        var total = 0;
+        var totalOverLimit = 0;
+        for (var car : cars) {
+            total++;
+            if (total > limit) {
+                totalOverLimit++;
+                // side effect
+            }
+        }
+        return totalOverLimit;
+    }
+
+    static int countCarsOverLimitWithUnnamedVariable(Collection<Car<?>> cars, int limit) {
+        var total = 0;
+        var totalOverLimit = 0;
+        for (var _ : cars) {
+            total++;
+            if (total > limit) {
+                totalOverLimit++;
+                // side effect
+            }
+        }
+        return totalOverLimit;
+    }
+
+    static void sendNotificationToCarsWithNamedVariable(Collection<Car<?>> cars) {
+        sendOneTimeNotification();
+        for (int i = 0; i < cars.size(); i++) {
+            // Notify car
+        }
+    }
+
+    static void sendNotificationToCarsWithUnnamedVariable(Collection<Car<?>> cars) {
+        for (int i = 0, _ = sendOneTimeNotification(); i < cars.size(); i++) {
+            // Notify car
+        }
+    }
+
+    private static int sendOneTimeNotification() {
+        System.out.println("Sending one time notification!");
+        return 1;
+    }
+
+    static Car<?> removeThreeCarsAndReturnFirstRemovedWithNamedVariables(Queue<Car<?>> cars) {
+        var x = cars.poll();
+        var y = cars.poll();
+        var z = cars.poll();
+        return x;
+    }
+
+    static Car<?> removeThreeCarsAndReturnFirstRemovedWithUnnamedVariables(Queue<Car<?>> cars) {
+        var car = cars.poll();
+        var _ = cars.poll();
+        var _ = cars.poll();
+        return car;
+    }
+
+    static void handleCarExceptionWithNamedVariables(Car<?> car) {
+        try {
+            someOperationThatFails(car);
+        } catch (IllegalStateException ex) {
+            System.out.println("Got an illegal state exception for: " + car.name());
+        } catch (RuntimeException ex) {
+            System.out.println("Got a runtime exception!");
+        }
+    }
+
+    static void handleCarExceptionWithUnnamedVariables(Car<?> car) {
+        try {
+            someOperationThatFails(car);
+        } catch (IllegalStateException | NumberFormatException _) {
+            System.out.println("Got an illegal state exception for: " + car.name());
+        } catch (RuntimeException _) {
+            System.out.println("Got a runtime exception!");
+        }
+    }
+
+    static void obtainTransactionAndUpdateCarWithNamedVariables(Car<?> car) {
+        try (var transaction = new Transaction()) {
+            updateCar(car);
+        }
+    }
+
+    static void obtainTransactionAndUpdateCarWithUnnamedVariables(Car<?> car) {
+        try (var _ = new Transaction()) {
+            updateCar(car);
+        }
+    }
+
+    static void updateCar(Car<?> car) {
+        // Some update logic
+        System.out.println("Car updated!");
+    }
+
+    static Map<String, List<Car<?>>> getCarsByFirstLetterWithNamedVariables(List<Car<?>> cars) {
+        Map<String, List<Car<?>>> carMap = new HashMap<>();
+        cars.forEach(car ->
+            carMap.computeIfAbsent(car.name().substring(0, 1), firstLetter -> new ArrayList<>()).add(car)
+        );
+        return carMap;
+    }
+
+    static Map<String, List<Car<?>>> getCarsByFirstLetterWithUnnamedVariables(List<Car<?>> cars) {
+        Map<String, List<Car<?>>> carMap = new HashMap<>();
+        cars.forEach(car ->
+            carMap.computeIfAbsent(car.name().substring(0, 1), _ -> new ArrayList<>()).add(car)
+        );
+        return carMap;
+    }
+
+    private static void someOperationThatFails(Car<?> car) {
+        throw new IllegalStateException("Triggered exception for: " + car.name());
+    }
+}

core-java-modules/core-java-21/src/main/java/com/baeldung/unnamedclasses/HelloWorld.java

@@ -0,0 +1,3 @@
+void main() {
+    System.out.println("Hello, World!");
+}

core-java-modules/core-java-21/src/main/java/com/baeldung/unnamedclasses/HelloWorldChild.java

@@ -0,0 +1,7 @@
+package com.baeldung.unnamedclasses;
+
+public class HelloWorldChild extends HelloWorldSuper {
+    void main() {
+        System.out.println("Hello, World!");
+    }
+}

core-java-modules/core-java-21/src/main/java/com/baeldung/unnamedclasses/HelloWorldSuper.java

@@ -0,0 +1,7 @@
+package com.baeldung.unnamedclasses;
+
+public class HelloWorldSuper {
+    public static void main(String[] args) {
+        System.out.println("Hello from the superclass");
+    }
+}

core-java-modules/core-java-21/src/main/java/com/baeldung/unnamedclasses/HelloWorldWithMethod.java

@@ -0,0 +1,6 @@
+private String getMessage() {
+    return "Hello, World!";
+}
+void main() {
+    System.out.println(getMessage());
+}

core-java-modules/core-java-21/src/test/java/com/baeldung/unnamed/variables/CarScenario.java

@@ -0,0 +1,13 @@
+package com.baeldung.unnamed.variables;
+
+import java.util.List;
+
+class CarScenario {
+
+    protected final List<Car<?>> cars = List.of(
+        new Car<>("Mitsubishi", "blue", new GasEngine()),
+        new Car<>("Toyota", "red", new ElectricEngine()),
+        new Car<>("Jaguar", "white", new HybridEngine())
+    );
+
+}

core-java-modules/core-java-21/src/test/java/com/baeldung/unnamed/variables/UnnamedPatternsUnitTest.java

@@ -0,0 +1,44 @@
+package com.baeldung.unnamed.variables;
+
+import static com.baeldung.unnamed.variables.UnnamedPatterns.getEngineTypeWithNamedPattern;
+import static com.baeldung.unnamed.variables.UnnamedPatterns.getEngineTypeWithUnnamedPattern;
+import static com.baeldung.unnamed.variables.UnnamedPatterns.getObjectsColorWithNamedPattern;
+import static com.baeldung.unnamed.variables.UnnamedPatterns.getObjectsColorWithSwitchAndNamedPattern;
+import static com.baeldung.unnamed.variables.UnnamedPatterns.getObjectsColorWithSwitchAndUnnamedPattern;
+import static com.baeldung.unnamed.variables.UnnamedPatterns.getObjectsColorWithUnnamedPattern;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class UnnamedPatternsUnitTest extends CarScenario {
+
+    @Test
+    public void whenExtractingColorWithNamedPatterns_thenReturnBlue() {
+        assertEquals("blue", getObjectsColorWithNamedPattern(cars.get(0)));
+    }
+
+    @Test
+    public void whenExtractingColorWithUnnamedPatterns_thenReturnBlue() {
+        assertEquals("blue", getObjectsColorWithUnnamedPattern(cars.get(0)));
+    }
+
+    @Test
+    public void whenExtractingColorWithSwitchAndNamedPatterns_thenReturnBlue() {
+        assertEquals("blue", getObjectsColorWithSwitchAndNamedPattern(cars.get(0)));
+    }
+
+    @Test
+    public void whenExtractingColorWithSwitchAndUnnamedPatterns_thenReturnBlue() {
+        assertEquals("blue", getObjectsColorWithSwitchAndUnnamedPattern(cars.get(0)));
+    }
+
+    @Test
+    public void whenExtractingEngineTypeWithNamedPatterns_thenReturnGas() {
+        assertEquals("gas", getEngineTypeWithNamedPattern(cars.get(0)));
+    }
+
+    @Test
+    public void whenExtractingEngineTypeWithUnnamedPatterns_thenReturnGas() {
+        assertEquals("gas", getEngineTypeWithUnnamedPattern(cars.get(0)));
+    }
+}

core-java-modules/core-java-21/src/test/java/com/baeldung/unnamed/variables/UnnamedVariablesUnitTest.java

@@ -0,0 +1,93 @@
+package com.baeldung.unnamed.variables;
+
+import static com.baeldung.unnamed.variables.UnnamedVariables.countCarsOverLimitWithNamedVariable;
+import static com.baeldung.unnamed.variables.UnnamedVariables.countCarsOverLimitWithUnnamedVariable;
+import static com.baeldung.unnamed.variables.UnnamedVariables.getCarsByFirstLetterWithNamedVariables;
+import static com.baeldung.unnamed.variables.UnnamedVariables.getCarsByFirstLetterWithUnnamedVariables;
+import static com.baeldung.unnamed.variables.UnnamedVariables.handleCarExceptionWithNamedVariables;
+import static com.baeldung.unnamed.variables.UnnamedVariables.handleCarExceptionWithUnnamedVariables;
+import static com.baeldung.unnamed.variables.UnnamedVariables.obtainTransactionAndUpdateCarWithNamedVariables;
+import static com.baeldung.unnamed.variables.UnnamedVariables.obtainTransactionAndUpdateCarWithUnnamedVariables;
+import static com.baeldung.unnamed.variables.UnnamedVariables.removeThreeCarsAndReturnFirstRemovedWithNamedVariables;
+import static com.baeldung.unnamed.variables.UnnamedVariables.removeThreeCarsAndReturnFirstRemovedWithUnnamedVariables;
+import static com.baeldung.unnamed.variables.UnnamedVariables.sendNotificationToCarsWithNamedVariable;
+import static com.baeldung.unnamed.variables.UnnamedVariables.sendNotificationToCarsWithUnnamedVariable;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.LinkedList;
+
+import org.junit.jupiter.api.Test;
+
+public class UnnamedVariablesUnitTest extends CarScenario {
+
+    @Test
+    public void whenCountingCarsOverLimitWithNamedVariables_thenShouldReturnOne() {
+        assertEquals(1, countCarsOverLimitWithNamedVariable(cars, 2));
+    }
+
+    @Test
+    public void whenCountingCarsOverLimitWithUnnamedVariables_thenShouldReturnOne() {
+        assertEquals(1, countCarsOverLimitWithUnnamedVariable(cars, 2));
+    }
+
+    @Test
+    public void whenNotifyingCarsWithNamedVariables_thenShouldNotFail() {
+        assertDoesNotThrow(() -> sendNotificationToCarsWithNamedVariable(cars));
+    }
+
+    @Test
+    public void whenNotifyingCarsWithUnnamedVariables_thenShouldNotFail() {
+        assertDoesNotThrow(() -> sendNotificationToCarsWithUnnamedVariable(cars));
+    }
+
+    @Test
+    public void whenPollingCarsWithNamedVariables_thenReturnFirstOneAndEmptyQueue() {
+        var carQueue = new LinkedList<>(cars);
+        assertEquals("Mitsubishi", removeThreeCarsAndReturnFirstRemovedWithNamedVariables(carQueue).name());
+        assertEquals(0, carQueue.size());
+    }
+
+    @Test
+    public void whenPollingCarsWithUnnamedVariables_thenReturnFirstOneAndEmptyQueue() {
+        var carQueue = new LinkedList<>(cars);
+        assertEquals("Mitsubishi", removeThreeCarsAndReturnFirstRemovedWithUnnamedVariables(carQueue).name());
+        assertEquals(0, carQueue.size());
+    }
+
+    @Test
+    public void whenHandlingExceptionWithNamedVariables_thenNoExceptionIsThrown() {
+        assertDoesNotThrow(() -> handleCarExceptionWithNamedVariables(cars.get(0)));
+    }
+
+    @Test
+    public void whenHandlingExceptionWithUnnamedVariables_thenNoExceptionIsThrown() {
+        assertDoesNotThrow(() -> handleCarExceptionWithUnnamedVariables(cars.get(0)));
+    }
+
+    @Test
+    public void whenHandlingTransactionUpdateWithNamedVariables_thenNoExceptionIsThrown() {
+        assertDoesNotThrow(() -> obtainTransactionAndUpdateCarWithNamedVariables(cars.get(0)));
+    }
+
+    @Test
+    public void whenHandlingTransactionUpdateWithUnnamedVariables_thenNoExceptionIsThrown() {
+        assertDoesNotThrow(() -> obtainTransactionAndUpdateCarWithUnnamedVariables(cars.get(0)));
+    }
+
+    @Test
+    public void whenGettingCarsByFirstLetterWithNamedVariables_thenHaveThreeKeys() {
+        var carsByLetter = getCarsByFirstLetterWithNamedVariables(cars);
+        assertEquals(1, carsByLetter.get("M").size());
+        assertEquals(1, carsByLetter.get("T").size());
+        assertEquals(1, carsByLetter.get("J").size());
+    }
+
+    @Test
+    public void whenGettingCarsByFirstLetterWithUnnamedVariables_thenHaveThreeKeys() {
+        var carsByLetter = getCarsByFirstLetterWithUnnamedVariables(cars);
+        assertEquals(1, carsByLetter.get("M").size());
+        assertEquals(1, carsByLetter.get("T").size());
+        assertEquals(1, carsByLetter.get("J").size());
+    }
+}

core-java-modules/core-java-9-streams/README.md

@@ -4,3 +4,4 @@ This module contains articles about Java 9 streams
 
 ### Relevant Articles: 
 - [How to Break from Java Stream forEach](https://www.baeldung.com/java-break-stream-foreach)
+- [Creating Stream of Regex Matches](https://www.baeldung.com/java-stream-regex-matches)

core-java-modules/core-java-arrays-convert/README.md

@@ -10,3 +10,4 @@ This module contains articles about arrays conversion in Java
 - [Convert Java Array to Iterable](https://www.baeldung.com/java-array-convert-to-iterable)
 - [Converting an int[] to HashSet in Java](https://www.baeldung.com/java-converting-int-array-to-hashset)
 - [Convert an ArrayList of String to a String Array in Java](https://www.baeldung.com/java-convert-string-arraylist-array)
+- [Convert Char Array to Int Array in Java](https://www.baeldung.com/java-convert-char-int-array)

core-java-modules/core-java-arrays-convert/src/main/java/com/baeldung/array/conversions/CharArrayToIntArrayUtils.java

@@ -0,0 +1,67 @@
+package com.baeldung.array.conversions;
+
+import java.util.Arrays;
+
+public class CharArrayToIntArrayUtils {
+
+    static int[] usingGetNumericValueMethod(char[] chars) {
+        if (chars == null) {
+            return null;
+        }
+
+        int[] ints = new int[chars.length];
+        for (int i = 0; i < chars.length; i++) {
+            ints[i] = Character.getNumericValue(chars[i]);
+        }
+
+        return ints;
+    }
+
+    static int[] usingDigitMethod(char[] chars) {
+        if (chars == null) {
+            return null;
+        }
+
+        int[] ints = new int[chars.length];
+        for (int i = 0; i < chars.length; i++) {
+            ints[i] = Character.digit(chars[i], 10);
+        }
+
+        return ints;
+    }
+
+    static int[] usingStreamApiMethod(char[] chars) {
+        if (chars == null) {
+            return null;
+        }
+
+        return new String(chars).chars()
+          .map(c -> c - 48)
+          .toArray();
+    }
+
+    static int[] usingParseIntMethod(char[] chars) {
+        if (chars == null) {
+            return null;
+        }
+
+        int[] ints = new int[chars.length];
+        for (int i = 0; i < chars.length; i++) {
+            ints[i] = Integer.parseInt(String.valueOf(chars[i]));
+        }
+
+        return ints;
+    }
+
+    static int[] usingArraysSetAllMethod(char[] chars) {
+        if (chars == null) {
+            return null;
+        }
+
+        int[] ints = new int[chars.length];
+        Arrays.setAll(ints, i -> Character.getNumericValue(chars[i]));
+
+        return ints;
+    }
+
+}

core-java-modules/core-java-arrays-convert/src/test/java/com/baeldung/array/conversions/CharArrayToIntArrayUtilsUnitTest.java

@@ -0,0 +1,54 @@
+package com.baeldung.array.conversions;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+import org.junit.jupiter.api.Test;
+
+class CharArrayToIntArrayUtilsUnitTest {
+
+    @Test
+    void givenCharArray_whenUsingGetNumericValueMethod_shouldGetIntArray() {
+        int[] expected = { 2, 3, 4, 5 };
+        char[] chars = { '2', '3', '4', '5' };
+        int[] result = CharArrayToIntArrayUtils.usingGetNumericValueMethod(chars);
+
+        assertArrayEquals(expected, result);
+    }
+
+    @Test
+    void givenCharArray_whenUsingDigitMethod_shouldGetIntArray() {
+        int[] expected = { 1, 2, 3, 6 };
+        char[] chars = { '1', '2', '3', '6' };
+        int[] result = CharArrayToIntArrayUtils.usingDigitMethod(chars);
+
+        assertArrayEquals(expected, result);
+    }
+
+    @Test
+    void givenCharArray_whenUsingStreamApi_shouldGetIntArray() {
+        int[] expected = { 9, 8, 7, 6 };
+        char[] chars = { '9', '8', '7', '6' };
+        int[] result = CharArrayToIntArrayUtils.usingStreamApiMethod(chars);
+
+        assertArrayEquals(expected, result);
+    }
+
+    @Test
+    void givenCharArray_whenUsingParseIntMethod_shouldGetIntArray() {
+        int[] expected = { 9, 8, 7, 6 };
+        char[] chars = { '9', '8', '7', '6' };
+        int[] result = CharArrayToIntArrayUtils.usingParseIntMethod(chars);
+
+        assertArrayEquals(expected, result);
+    }
+
+    @Test
+    void givenCharArray_whenUsingArraysSetAllMethod_shouldGetIntArray() {
+        int[] expected = { 4, 9, 2, 3 };
+        char[] chars = { '4', '9', '2', '3' };
+        int[] result = CharArrayToIntArrayUtils.usingArraysSetAllMethod(chars);
+
+        assertArrayEquals(expected, result);
+    }
+
+}

core-java-modules/core-java-arrays-guides/README.md

@@ -9,3 +9,4 @@ This module contains complete guides about arrays in Java
 - [Guide to ArrayStoreException](https://www.baeldung.com/java-arraystoreexception)
 - [Creating a Generic Array in Java](https://www.baeldung.com/java-generic-array)
 - [Maximum Size of Java Arrays](https://www.baeldung.com/java-arrays-max-size)
+- [Merge Two Arrays and Remove Duplicates in Java](https://www.baeldung.com/java-merge-two-arrays-delete-duplicates)

core-java-modules/core-java-arrays-operations-advanced-2/README.md

@@ -0,0 +1,2 @@
+## Relevant Articles
+- [Find the Middle Element of an Array in Java](https://www.baeldung.com/java-array-middle-item)

core-java-modules/core-java-arrays-operations-advanced/README.md

@@ -14,4 +14,3 @@ This module contains articles about advanced operations on arrays in Java. They
 - [Slicing Arrays in Java](https://www.baeldung.com/java-slicing-arrays)
 - [Combining Two or More Byte Arrays](https://www.baeldung.com/java-concatenate-byte-arrays)
 - [Calculating the Sum of Two Arrays in Java](https://www.baeldung.com/java-sum-arrays-element-wise)
-- [Find the Middle Element of an Array in Java](https://www.baeldung.com/java-array-middle-item)

core-java-modules/core-java-char/README.md

@@ -5,3 +5,4 @@ This module contains articles about Java Character Class
 ### Relevant Articles: 
 - [Character#isAlphabetic vs. Character#isLetter](https://www.baeldung.com/java-character-isletter-isalphabetic)
 - [Difference Between Java’s “char” and “String”](https://www.baeldung.com/java-char-vs-string)
+- [Increment Character in Java](https://www.baeldung.com/java-char-sequence)

core-java-modules/core-java-char/src/test/java/com/baeldung/incrementchar/IncrementCharUnitTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.incrementchar;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+class IncrementCharUnitTest {
+    @Test
+    void whenUsingForLoop_thenGenerateCharacters(){
+        final List<Character> allCapitalCharacters = Arrays.asList('A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z');
+        List<Character> characters = new ArrayList<>();
+        for (char character = 'A'; character <= 'Z'; character++) {
+            characters.add(character);
+        }
+        Assertions.assertEquals(characters, allCapitalCharacters);
+    }
+
+    @Test
+    void whenUsingStreams_thenGenerateCharacters() {
+        final List<Character> allCapitalCharacters = Arrays.asList('A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z');
+        final List<Character> characters = IntStream.rangeClosed('A', 'Z').mapToObj(c -> (char) c).collect(Collectors.toList());
+        Assertions.assertEquals(characters, allCapitalCharacters);
+    }
+}

core-java-modules/core-java-collections-5/README.md

@@ -5,4 +5,6 @@
 ### Relevant Articles:
 - [Introduction to Roaring Bitmap](https://www.baeldung.com/java-roaring-bitmap-intro)
 - [Creating Custom Iterator in Java](https://www.baeldung.com/java-creating-custom-iterator)
+- [Difference Between Arrays.sort() and Collections.sort()](https://www.baeldung.com/java-arrays-collections-sort-methods)
+- [Skipping the First Iteration in Java](https://www.baeldung.com/java-skip-first-iteration)
 - More articles: [[<-- prev]](/core-java-modules/core-java-collections-4)

core-java-modules/core-java-collections-5/src/main/java/com/baeldung/skippingfirstelement/SkipFirstElementExample.java

@@ -0,0 +1,126 @@
+package com.baeldung.skippingfirstelement;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+
+public class SkipFirstElementExample {
+
+    private final List<String> stringList = new ArrayList<>();
+    private final Set<String> stringSet = new HashSet<>();
+    private final Map<String, String> stringMap = new HashMap<>();
+
+    public SkipFirstElementExample() {
+        // Initializing a List
+        stringList.add("Monday");
+        stringList.add("Tuesday");
+        stringList.add("Wednesday");
+        stringList.add("Thursday");
+        stringList.add("Friday");
+        stringList.add("Saturday");
+        stringList.add("Sunday");
+        // Initializing a Set
+        stringSet.add("Monday");
+        stringSet.add("Tuesday");
+        stringSet.add("Wednesday");
+        stringSet.add("Thursday");
+        stringSet.add("Friday");
+        stringSet.add("Saturday");
+        stringSet.add("Sunday");
+        // Initializing a Map
+        stringMap.put("Monday", "The day when coffee is a life support system.");
+        stringMap.put("Tuesday", "The day you realize that Monday's optimism was a lie.");
+        stringMap.put("Wednesday", "Hump Day, or as it's known, the 'Is it Friday yet?' day.");
+        stringMap.put("Thursday", "The day that says, 'Hold my beer, Friday is coming!'");
+        stringMap.put("Friday", "The golden child of the weekdays. The superhero of the workweek.");
+        stringMap.put("Saturday", "The day of rest? More like the day of 'What can I binge-watch next?'");
+        stringMap.put("Sunday", "The day before you have to adult again.");
+    }
+
+    void skippingFirstElementInListWithForLoop(List<String> stringList) {
+        for (int i = 1; i < stringList.size(); i++) {
+            process(stringList.get(i));
+        }
+    }
+
+    void skippingFirstElementInListWithWhileLoop(List<String> stringList) {
+        final Iterator<String> iterator = stringList.iterator();
+        if (iterator.hasNext()) {
+            iterator.next();
+        }
+        while (iterator.hasNext()) {
+            process(iterator.next());
+        }
+    }
+
+    void skippingFirstElementInSetWithWhileLoop(Set<String> stringSet) {
+        final Iterator<String> iterator = stringSet.iterator();
+        if (iterator.hasNext()) {
+            iterator.next();
+        }
+        while (iterator.hasNext()) {
+            process(iterator.next());
+        }
+    }
+
+    void skippingFirstElementInListWithWhileLoopStoringFirstElement(List<String> stringList) {
+        final Iterator<String> iterator = stringList.iterator();
+        String firstElement = null;
+        if (iterator.hasNext()) {
+            firstElement = iterator.next();
+        }
+        while (iterator.hasNext()) {
+            process(iterator.next());
+            // additional logic using fistElement
+        }
+    }
+
+    void skippingFirstElementInMapWithStreamSkip(Map<String, String> stringMap) {
+        stringMap.entrySet().stream().skip(1).forEach(this::process);
+    }
+
+    void skippingFirstElementInListWithSubList(List<String> stringList) {
+        for (final String element : stringList.subList(1, stringList.size())) {
+            process(element);
+        }
+    }
+
+    void skippingFirstElementInListWithForLoopWithAdditionalCheck(List<String> stringList) {
+        for (int i = 0; i < stringList.size(); i++) {
+            if (i == 0) {
+                // do something else
+            } else {
+                process(stringList.get(i));
+            }
+        }
+    }
+
+    void skippingFirstElementInListWithWhileLoopWithCounter(List<String> stringList) {
+        int counter = 0;
+        while (counter < stringList.size()) {
+            if (counter != 0) {
+                process(stringList.get(counter));
+            }
+            ++counter;
+        }
+    }
+
+    void skippingFirstElementInListWithReduce(List<String> stringList) {
+        stringList.stream().reduce((skip, element) -> {
+            process(element);
+            return element;
+        });
+    }
+
+    protected void process(String string) {
+        System.out.println(string);
+    }
+    protected void process(Entry<String, String> mapEntry) {
+        System.out.println(mapEntry);
+    }
+}

core-java-modules/core-java-collections-5/src/test/java/com/baeldung/skippingfirstelement/SkipFirstElementExampleUnitTest.java

@@ -0,0 +1,122 @@
+package com.baeldung.skippingfirstelement;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.condition.EnabledForJreRange;
+import org.junit.jupiter.api.condition.JRE;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+@EnabledForJreRange(min = JRE.JAVA_9)
+class SkipFirstElementExampleUnitTest {
+
+    private static TestableSkipFirstElement testableSkip = new TestableSkipFirstElement();
+
+    @BeforeEach
+    void setup() {
+        testableSkip.reset();
+    }
+
+    private static Stream<Arguments> listProvider() {
+        return Stream.of(
+            Arguments.of(
+                List.of("Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"),
+                List.of("Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"))
+        );
+    }
+
+    private static Stream<Arguments> mapProvider() {
+        return Stream.of(
+            Arguments.of(
+                Map.of(
+                    "Monday", "The day when coffee is a life support system.",
+                    "Tuesday", "The day you realize that Monday's optimism was a lie.",
+                    "Wednesday", "Hump Day, or as it's known, the 'Is it Friday yet?' day.",
+                    "Thursday", "The day that says, 'Hold my beer, Friday is coming!'",
+                    "Friday", "The golden child of the weekdays. The superhero of the workweek.",
+                    "Saturday", "The day of rest? More like the day of 'What can I binge-watch next?'",
+                    "Sunday", "The day before you have to adult again."
+                )
+            )
+        );
+    }
+
+    @ParameterizedTest
+    @MethodSource("listProvider")
+    void skippingFirstElementInListWithForLoop(List<String> input, List<String> expected) {
+        testableSkip.skippingFirstElementInListWithForLoop(input);
+        List<?> actual = testableSkip.getResult();
+        assertEquals(actual, expected);
+    }
+
+    @ParameterizedTest
+    @MethodSource("listProvider")
+    void skippingFirstElementInListWithWhileLoop(List<String> input, List<String> expected) {
+        testableSkip.skippingFirstElementInListWithWhileLoop(input);
+        List<?> actual = testableSkip.getResult();
+        assertEquals(actual, expected);
+    }
+
+    @ParameterizedTest
+    @MethodSource("listProvider")
+    void skippingFirstElementInSetWithWhileLoop(List<String> input) {
+        testableSkip.skippingFirstElementInSetWithWhileLoop(new HashSet<>(input));
+        Set<?> actual = new HashSet<>(testableSkip.getResult());
+        assertEquals(actual.size(), input.size() - 1);
+    }
+
+    @ParameterizedTest
+    @MethodSource("listProvider")
+    void skippingFirstElementInListWithWhileLoopStoringFirstElement(List<String> input, List<String> expected) {
+        testableSkip.skippingFirstElementInListWithWhileLoopStoringFirstElement(input);
+        List<?> actual = testableSkip.getResult();
+        assertEquals(actual, expected);
+    }
+
+    @ParameterizedTest
+    @MethodSource("mapProvider")
+    void skippingFirstElementInMapWithStreamSkip(Map<String, String> input) {
+        testableSkip.skippingFirstElementInMapWithStreamSkip(input);
+        List<?> actual = testableSkip.getResult();
+        assertEquals(actual.size(), input.size() - 1);
+    }
+
+    @ParameterizedTest
+    @MethodSource("listProvider")
+    void skippingFirstElementInListWithSubList(List<String> input, List<String> expected) {
+        testableSkip.skippingFirstElementInListWithSubList(input);
+        List<?> actual = testableSkip.getResult();
+        assertEquals(actual, expected);
+    }
+
+    @ParameterizedTest
+    @MethodSource("listProvider")
+    void skippingFirstElementInListWithForLoopWithAdditionalCheck(List<String> input, List<String> expected) {
+        testableSkip.skippingFirstElementInListWithForLoopWithAdditionalCheck(input);
+        List<?> actual = testableSkip.getResult();
+        assertEquals(actual, expected);
+    }
+
+    @ParameterizedTest
+    @MethodSource("listProvider")
+    void skippingFirstElementInListWithWhileLoopWithCounter(List<String> input, List<String> expected) {
+        testableSkip.skippingFirstElementInListWithWhileLoopWithCounter(input);
+        List<?> actual = testableSkip.getResult();
+        assertEquals(actual, expected);
+    }
+
+    @ParameterizedTest
+    @MethodSource("listProvider")
+    void skippingFirstElementInListWithReduce(List<String> input, List<String> expected) {
+        testableSkip.skippingFirstElementInListWithReduce(input);
+        List<?> actual = testableSkip.getResult();
+        assertEquals(actual, expected);
+    }
+}

core-java-modules/core-java-collections-5/src/test/java/com/baeldung/skippingfirstelement/TestableSkip.java

@@ -0,0 +1,10 @@
+package com.baeldung.skippingfirstelement;
+
+import java.util.List;
+
+public interface TestableSkip {
+
+    void reset();
+
+    List<?> getResult();
+}

core-java-modules/core-java-collections-5/src/test/java/com/baeldung/skippingfirstelement/TestableSkipFirstElement.java

@@ -0,0 +1,37 @@
+package com.baeldung.skippingfirstelement;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map.Entry;
+
+public class TestableSkipFirstElement extends SkipFirstElementExample implements TestableSkip {
+
+
+    private List<String> processedList = new ArrayList<>();
+    private List<Entry<String, String>> processedEntryList = new ArrayList<>();
+
+    @Override
+    public void process(String string) {
+        processedList.add(string);
+    }
+
+    @Override
+    public void process(Entry<String, String> stringEntry) {
+        processedEntryList.add(stringEntry);
+    }
+
+    @Override
+    public void reset() {
+        processedList.clear();
+        processedEntryList.clear();
+    }
+
+    @Override
+    public List<?> getResult() {
+        if (!processedList.isEmpty())
+            return processedList;
+        return processedEntryList;
+    }
+
+
+}

core-java-modules/core-java-collections-array-list-2/README.md

@@ -0,0 +1,6 @@
+## Core Java Collections ArrayList
+
+This module contains articles about the Java ArrayList collection
+
+### Relevant Articles:
+- [Create an ArrayList with Multiple Object Types](https://www.baeldung.com/java-arraylist-multiple-object-types)

core-java-modules/core-java-collections-array-list-2/pom.xml

@@ -0,0 +1,32 @@
+<project
+    xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-collections-array-list-2</artifactId>
+    <name>core-java-collections-array-list-2</name>
+    <packaging>jar</packaging>
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+    
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven-compiler-plugin.source}</source>
+                    <target>${maven-compiler-plugin.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+    
+    <properties>
+        <maven-compiler-plugin.source>17</maven-compiler-plugin.source>
+        <maven-compiler-plugin.target>17</maven-compiler-plugin.target>
+    </properties>
+</project>

core-java-modules/core-java-collections-array-list-2/src/main/java/com/baeldung/list/multipleobjecttypes/AlternativeMultipeTypeList.java

@@ -0,0 +1,51 @@
+package com.baeldung.list.multipleobjecttypes;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.function.Predicate;
+
+public class AlternativeMultipeTypeList {
+
+    public static void main(String[] args) {
+        // List of Parent Class
+        ArrayList<Number> myList = new ArrayList<>();
+        myList.add(1.2);
+        myList.add(2);
+        myList.add(-3.5);
+
+        // List of Interface type
+        ArrayList<Map> diffMapList = new ArrayList<>();
+        diffMapList.add(new HashMap<>());
+        diffMapList.add(new TreeMap<>());
+        diffMapList.add(new LinkedHashMap<>());
+
+        // List of Custom Object
+        ArrayList<CustomObject> objList = new ArrayList<>();
+        objList.add(new CustomObject("String"));
+        objList.add(new CustomObject(2));
+
+        // List via Functional Interface
+        List<Object> dataList = new ArrayList<>();
+
+        Predicate<Object> myPredicate = inputData -> (inputData instanceof String || inputData instanceof Integer);
+
+        UserFunctionalInterface myInterface = (listObj, data) -> {
+            if (myPredicate.test(data))
+                listObj.add(data);
+            else
+                System.out.println("Skipping input as data not allowed for class: " + data.getClass()
+                    .getSimpleName());
+            return listObj;
+        };
+
+        myInterface.addToList(dataList, Integer.valueOf(2));
+        myInterface.addToList(dataList, Double.valueOf(3.33));
+        myInterface.addToList(dataList, "String Value");
+        myInterface.printList(dataList);
+    }
+
+}

core-java-modules/core-java-collections-array-list-2/src/main/java/com/baeldung/list/multipleobjecttypes/CustomObject.java

@@ -0,0 +1,22 @@
+package com.baeldung.list.multipleobjecttypes;
+
+public class CustomObject {
+    String classData;
+    Integer intData;
+
+    CustomObject(String classData) {
+        this.classData = classData;
+    }
+
+    CustomObject(Integer intData) {
+        this.intData = intData;
+    }
+
+    public String getClassData() {
+        return this.classData;
+    }
+
+    public Integer getIntData() {
+        return this.intData;
+    }
+}

core-java-modules/core-java-collections-array-list-2/src/main/java/com/baeldung/list/multipleobjecttypes/MultipleObjectTypeArrayList.java

@@ -0,0 +1,40 @@
+package com.baeldung.list.multipleobjecttypes;
+
+import java.math.BigInteger;
+import java.time.LocalDate;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class MultipleObjectTypeArrayList {
+
+    public static void main(String[] args) {
+
+        ArrayList<Object> multiTypeList = new ArrayList<>();
+
+        multiTypeList.add(Integer.valueOf(10));
+        multiTypeList.add(Double.valueOf(11.5));
+        multiTypeList.add("String Data");
+        multiTypeList.add(Arrays.asList(1, 2, 3));
+        multiTypeList.add(new CustomObject("Class Data"));
+        multiTypeList.add(BigInteger.valueOf(123456789));
+        multiTypeList.add(LocalDate.of(2023, 9, 19));
+
+        for (Object dataObj : multiTypeList) {
+            if (dataObj instanceof Integer intData)
+                System.out.println("Integer Data : " + intData);
+            else if (dataObj instanceof Double doubleData)
+                System.out.println("Double Data : " + doubleData);
+            else if (dataObj instanceof String stringData)
+                System.out.println("String Data : " + stringData);
+            else if (dataObj instanceof List<?> intList)
+                System.out.println("List Data : " + intList);
+            else if (dataObj instanceof CustomObject customObj)
+                System.out.println("CustomObject Data : " + customObj.getClassData());
+            else if (dataObj instanceof BigInteger bigIntData)
+                System.out.println("BigInteger Data : " + bigIntData);
+            else if (dataObj instanceof LocalDate localDate)
+                System.out.println("LocalDate Data : " + localDate.toString());
+        }
+    }
+}

core-java-modules/core-java-collections-array-list-2/src/main/java/com/baeldung/list/multipleobjecttypes/UserFunctionalInterface.java

@@ -0,0 +1,18 @@
+package com.baeldung.list.multipleobjecttypes;
+
+import java.util.List;
+
+@FunctionalInterface
+public interface UserFunctionalInterface {
+
+    List<Object> addToList(List<Object> list, Object data);
+
+    default void printList(List<Object> dataList) {
+        for (Object data : dataList) {
+            if (data instanceof String stringData)
+                System.out.println("String Data: " + stringData);
+            if (data instanceof Integer intData)
+                System.out.println("Integer Data: " + intData);
+        }
+    }
+}

core-java-modules/core-java-collections-conversions-3/README.md

@@ -3,3 +3,4 @@
 This module contains articles about conversions among Collection types in Java.
 
 ### Relevant Articles:
+- [Converting HashMap Values to an ArrayList in Java](https://www.baeldung.com/java-hashmap-arraylist)

core-java-modules/core-java-collections-list-6/README.md

@@ -0,0 +1,2 @@
+## Relevant Articles
+- [Check if a List Contains a String Element While Ignoring Case](https://www.baeldung.com/java-list-search-case-insensitive)

core-java-modules/core-java-collections-list-6/pom.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-collections-list-6</artifactId>
+    <name>core-java-collections-list-6</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+</project>

core-java-modules/core-java-collections-list-6/src/test/java/com/baeldung/lists/StringListCaseInsensitiveContainsUnitTest.java

@@ -0,0 +1,44 @@
+package com.baeldung.lists;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+public class StringListCaseInsensitiveContainsUnitTest {
+    private final static List<String> THE_LIST = List.of("Game of Thrones", "Forrest Gump", "American Beauty", "Pretty Woman", "Catch Me If You Can");
+
+    @Test
+    void whenUsingContains_thenGetExpectedResult() {
+        assertFalse(THE_LIST.contains("catch me if you can"));
+    }
+
+    boolean ignoreCaseContainsForLoop(List<String> list, String value) {
+        for (String e : list) {
+            if (value.equalsIgnoreCase(e))
+                return true;
+        }
+        return false;
+    }
+
+    @Test
+    void whenUsingIgnoreCaseContainsForLoop_thenGetExpectedResult() {
+        assertTrue(ignoreCaseContainsForLoop(THE_LIST, "CATCH me if you CAN"));
+        assertTrue(ignoreCaseContainsForLoop(THE_LIST, "game of thrones"));
+        assertFalse(ignoreCaseContainsForLoop(THE_LIST, "The Godfather"));
+    }
+
+    @Test
+    void whenUsingIgnoreCaseContainsStream_thenGetExpectedResult() {
+        assertTrue(THE_LIST.stream()
+          .anyMatch(e -> e.equalsIgnoreCase("CATCH me if you CAN")));
+
+        assertTrue(THE_LIST.stream()
+          .anyMatch("game of thrones"::equalsIgnoreCase));
+
+        assertFalse(THE_LIST.stream()
+          .anyMatch("The Godfather"::equalsIgnoreCase));
+    }
+}

core-java-modules/core-java-collections-maps-6/src/test/com/baeldung/objecttomap/ObjectToMapUnitTest.java

@@ -1,76 +0,0 @@
-package java.com.baeldung.objecttomap;
-import com.google.gson.Gson;
-import org.junit.Assert;
-import org.junit.Test;
-import wiremock.com.fasterxml.jackson.core.type.TypeReference;
-import wiremock.com.fasterxml.jackson.databind.ObjectMapper;
-import wiremock.com.google.common.reflect.TypeToken;
-import java.lang.reflect.Field;
-import java.util.HashMap;
-import java.util.Map;
-
-public class ObjectToMapUnitTest {
-    Employee employee = new Employee("John", 3000.0);
-
-    @Test
-    public void givenJavaObject_whenUsingReflection_thenConvertToMap() throws IllegalAccessException {
-        Map<String, Object> map = convertUsingReflection(employee);
-        Assert.assertEquals(employee.getName(), map.get("name"));
-        Assert.assertEquals(employee.getSalary(), map.get("salary"));
-    }
-
-    private Map<String, Object> convertUsingReflection(Object object) throws IllegalAccessException {
-        Map<String, Object> map = new HashMap<>();
-        Field[] fields = object.getClass().getDeclaredFields();
-
-        for (Field field : fields) {
-            field.setAccessible(true);
-            map.put(field.getName(), field.get(object));
-        }
-
-        return map;
-    }
-
-    @Test
-    public void givenJavaObject_whenUsingJackson_thenConvertToMap() {
-        ObjectMapper objectMapper = new ObjectMapper();
-        Map<String, Object> map = objectMapper.convertValue(employee, new TypeReference<Map<String, Object>>() {});
-        Assert.assertEquals(employee.getName(), map.get("name"));
-        Assert.assertEquals(employee.getSalary(), map.get("salary"));
-    }
-
-    @Test
-    public void givenJavaObject_whenUsingGson_thenConvertToMap() {
-        Gson gson = new Gson();
-        String json = gson.toJson(employee);
-        Map<String, Object> map = gson.fromJson(json, new TypeToken<Map<String, Object>>() {}.getType());
-        Assert.assertEquals(employee.getName(), map.get("name"));
-        Assert.assertEquals(employee.getSalary(), map.get("salary"));
-    }
-
-    private static class Employee {
-        private String name;
-        private Double salary;
-
-        public Employee(String name, Double salary) {
-            this.name = name;
-            this.salary = salary;
-        }
-
-        public String getName() {
-            return name;
-        }
-
-        public void setName(String name) {
-            this.name = name;
-        }
-
-        public Double getSalary() {
-            return salary;
-        }
-
-        public void setSalary(Double age) {
-            this.salary = salary;
-        }
-    }
-}

core-java-modules/core-java-collections-maps-6/src/test/java/com/baeldung/objecttomap/ObjectToMapUnitTest.java

@@ -0,0 +1,128 @@
+package com.baeldung.objecttomap;
+
+import static org.junit.Assert.assertEquals;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.common.reflect.TypeToken;
+import com.google.gson.Gson;
+import org.junit.Test;
+import java.lang.reflect.Field;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.SortedMap;
+import java.util.TreeMap;
+import java.util.stream.Collectors;
+
+public class ObjectToMapUnitTest {
+    Employee employee = new Employee("John", 3000.0);
+
+    @Test
+    public void givenJavaObject_whenUsingReflection_thenConvertToMap() throws IllegalAccessException {
+        Map<String, Object> map = convertUsingReflection(employee);
+        assertEquals(employee.getName(), map.get("name"));
+        assertEquals(employee.getSalary(), map.get("salary"));
+    }
+
+    private Map<String, Object> convertUsingReflection(Object object) throws IllegalAccessException {
+        Map<String, Object> map = new HashMap<>();
+        Field[] fields = object.getClass().getDeclaredFields();
+
+        for (Field field : fields) {
+            field.setAccessible(true);
+            map.put(field.getName(), field.get(object));
+        }
+
+        return map;
+    }
+
+    @Test
+    public void givenJavaObject_whenUsingJackson_thenConvertToMap() {
+        ObjectMapper objectMapper = new ObjectMapper();
+        Map<String, Object> map = objectMapper.convertValue(employee, new TypeReference<Map<String, Object>>() {});
+        assertEquals(employee.getName(), map.get("name"));
+        assertEquals(employee.getSalary(), map.get("salary"));
+    }
+
+    @Test
+    public void givenJavaObject_whenUsingGson_thenConvertToMap() {
+        Gson gson = new Gson();
+        String json = gson.toJson(employee);
+        Map<String, Object> map = gson.fromJson(json, new TypeToken<Map<String, Object>>() {}.getType());
+        assertEquals(employee.getName(), map.get("name"));
+        assertEquals(employee.getSalary(), map.get("salary"));
+    }
+
+    @Test
+    public void given_UnsortedMap_whenSortingByValueDescending_thenValuesAreInDescendingOrder() {
+        Map<String, Integer> unsortedMap = new HashMap<>();
+        unsortedMap.put("one", 1);
+        unsortedMap.put("three", 3);
+        unsortedMap.put("five", 5);
+        unsortedMap.put("two", 2);
+        unsortedMap.put("four", 4);
+
+        Map<String, Integer> sortedMap = sortMapByValueDescending(unsortedMap);
+
+        assertEquals(5, sortedMap.size());
+        final Iterator<Integer> iterator = sortedMap.values().iterator();
+        assertEquals(5, (int) iterator.next());
+        assertEquals(4, (int) iterator.next());
+        assertEquals(3, (int) iterator.next());
+        assertEquals(2, (int) iterator.next());
+        assertEquals(1, (int) iterator.next());
+    }
+
+    @Test
+    public void given_UnsortedMap_whenUsingTreeMap_thenKeysAreInDescendingOrder() {
+        SortedMap<String, Integer> treeMap = new TreeMap<>(Comparator.reverseOrder());
+        treeMap.put("one", 1);
+        treeMap.put("three", 3);
+        treeMap.put("five", 5);
+        treeMap.put("two", 2);
+        treeMap.put("four", 4);
+
+        assertEquals(5, treeMap.size());
+        final Iterator<String> iterator = treeMap.keySet().iterator();
+        assertEquals("two", iterator.next());
+        assertEquals("three", iterator.next());
+        assertEquals("one", iterator.next());
+        assertEquals("four", iterator.next());
+        assertEquals("five", iterator.next());
+    }
+
+    private static class Employee {
+        private String name;
+        private Double salary;
+
+        public Employee(String name, Double salary) {
+            this.name = name;
+            this.salary = salary;
+        }
+
+        public String getName() {
+            return name;
+        }
+
+        public void setName(String name) {
+            this.name = name;
+        }
+
+        public Double getSalary() {
+            return salary;
+        }
+
+        public void setSalary(Double age) {
+            this.salary = salary;
+        }
+    }
+
+    public static <K, V extends Comparable<? super V>> Map<K, V> sortMapByValueDescending(Map<K, V> map) {
+        return map.entrySet().stream()
+                .sorted(Map.Entry.<K, V>comparingByValue().reversed())
+                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (e1, e2) -> e1, LinkedHashMap::new));
+    }
+}

core-java-modules/core-java-collections-maps-7/README.md

@@ -0,0 +1 @@
+## Relevant Articles

core-java-modules/core-java-collections-maps-7/pom.xml

@@ -0,0 +1,78 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-collections-maps-7</artifactId>
+    <name>core-java-collections-maps-7</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <artifactId>core-java-modules</artifactId>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+
+    <properties>
+        <spring.version>5.2.5.RELEASE</spring.version>
+    </properties>
+    <dependencies>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+            <version>2.12.4</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>1.36</version>
+        </dependency>
+        <dependency>
+            <groupId>com.google.code.gson</groupId>
+            <artifactId>gson</artifactId>
+            <version>2.8.9</version>
+        </dependency>
+        <dependency>
+            <groupId>org.json</groupId>
+            <artifactId>json</artifactId>
+            <version>20230227</version>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.13.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>5.8.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>5.8.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.13.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>5.8.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.13.1</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>

core-java-modules/core-java-collections-maps-7/src/main/java/com/baeldung/map/ConvertHashMapStringToHashMapObjectUsingtoString.java

@@ -0,0 +1,60 @@
+package com.baeldung.map;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class ConvertHashMapStringToHashMapObjectUsingtoString {
+    public String name;
+    public int age;
+
+    public ConvertHashMapStringToHashMapObjectUsingtoString(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public static ConvertHashMapStringToHashMapObjectUsingtoString deserializeCustomObject(String valueString) {
+        if (valueString.startsWith("{") && valueString.endsWith("}")) {
+            valueString = valueString.substring(1, valueString.length() - 1);
+            String[] parts = valueString.split(",");
+            String name = null;
+            int age = -1;
+            for (String part : parts) {
+                String[] keyValue = part.split("=");
+                if (keyValue.length == 2) {
+                    String key = keyValue[0].trim();
+                    String val = keyValue[1].trim();
+                    if (key.equals("name")) {
+                        name = val;
+                    } else if (key.equals("age")) {
+                        age = Integer.parseInt(val);
+                    }
+                }
+            }
+            if (name != null && age >= 0) {
+                return new ConvertHashMapStringToHashMapObjectUsingtoString(name, age);
+            }
+        }
+        return new ConvertHashMapStringToHashMapObjectUsingtoString("", -1);
+    }
+
+    public static void main(String[] args) {
+        String hashMapString = "{key1={name=John, age=30}, key2={name=Alice, age=25}}";
+        String keyValuePairs = hashMapString.replaceAll("[{}\\s]", "");
+        String[] pairs = keyValuePairs.split(",");
+        Map<String, ConvertHashMapStringToHashMapObjectUsingtoString> actualHashMap = new HashMap<>();
+        for (String pair : pairs) {
+            String[] keyValue = pair.split("=");
+            if (keyValue.length == 2) {
+                String key = keyValue[0];
+                ConvertHashMapStringToHashMapObjectUsingtoString value = deserializeCustomObject(keyValue[1]);
+                actualHashMap.put(key, value);
+            }
+        }
+        System.out.println(actualHashMap);
+    }
+
+    @Override
+    public String toString() {
+        return "{name=" + name + ", age=" + age + "}";
+    }
+}

core-java-modules/core-java-collections-maps-7/src/test/java/com/baeldung/map/ConvertHashMapStringToHashMapObjectUsingtoStringUnitTest.java

@@ -0,0 +1,31 @@
+package com.baeldung.map;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class ConvertHashMapStringToHashMapObjectUsingtoStringUnitTest {
+
+    @Test
+    void givenValidCustomObject_whenSerializing_thenSerializedStringIsCorrect() {
+        ConvertHashMapStringToHashMapObjectUsingtoString customObject = new ConvertHashMapStringToHashMapObjectUsingtoString("John", 30);
+        String expectedSerializedString = "{name=John, age=30}";
+        assertEquals(expectedSerializedString, customObject.toString());
+    }
+
+    @Test
+    void givenValidSerializedString_whenDeserializing_thenCustomObjectIsCorrect() {
+        String serializedString = "{name=Alice, age=25}";
+        ConvertHashMapStringToHashMapObjectUsingtoString customObject = ConvertHashMapStringToHashMapObjectUsingtoString.deserializeCustomObject(serializedString);
+        assertEquals("Alice", customObject.name);
+        assertEquals(25, customObject.age);
+    }
+
+    @Test
+    void givenInvalidSerializedString_whenDeserializing_thenDefaultCustomObjectIsCreated() {
+        String invalidSerializedString = "{invalidString}";
+        ConvertHashMapStringToHashMapObjectUsingtoString customObject = ConvertHashMapStringToHashMapObjectUsingtoString.deserializeCustomObject(invalidSerializedString);
+        assertEquals("", customObject.name);
+        assertEquals(-1, customObject.age);
+    }
+}

core-java-modules/core-java-datetime-conversion/src/test/java/com/baeldung/epochtolocaldate/EpochTimeToLocalDateTimeConverterUnitTest.java

@@ -12,10 +12,10 @@ public class EpochTimeToLocalDateTimeConverterUnitTest {
     @Test
     public void testConvertEpochTimeToLocalDateTime() {
         long epochTimeMillis = 1624962431000L; // Example epoch time in milliseconds
-        LocalDateTime expectedDateTime = LocalDateTime.of(2021, 6, 29, 12, 13, 51);
+        LocalDateTime expectedDateTime = LocalDateTime.of(2021, 6, 29, 10, 27, 11);
 
         Instant instant = Instant.ofEpochMilli(epochTimeMillis);
-        ZoneId zoneId = ZoneId.systemDefault();
+        ZoneId zoneId = ZoneId.of("UTC");
         LocalDateTime actualDateTime = instant.atZone(zoneId).toLocalDateTime();
 
         assertEquals(expectedDateTime, actualDateTime);

core-java-modules/core-java-documentation/README.md

@@ -3,4 +3,4 @@
 ### Relevant Articles: 
 
 - [Introduction to Javadoc](http://www.baeldung.com/javadoc)
-
+- [Code Snippets in Java API Documentation](https://www.baeldung.com/java-doc-code-snippets)

core-java-modules/core-java-documentation/src/main/java/com/baeldung/snippettag/GreetingsExternalSnippet.java

@@ -0,0 +1,18 @@
+package com.baeldung.snippettag;
+
+/**
+ * 
+ * External code snippet showing the loop process in binary search method.
+ * {@snippet class="BinarySearch" region="binary"}
+ * 
+ * Time Zone 
+ * {@snippet file="application.properties" region="zone"} 
+ *
+ */
+
+public class GreetingsExternalSnippet {
+    public void helloBinarySearch() {
+        System.out.println("Hi, it's great knowing that binary search uses a loop under the hood");
+    }
+
+}

core-java-modules/core-java-documentation/src/main/java/com/baeldung/snippettag/GreetingsHighlightTag.java

@@ -0,0 +1,35 @@
+package com.baeldung.snippettag;
+
+
+/**
+ * The code below shows a full highlighted line
+ * {@snippet :
+ * public void helloBaeldung() {
+ *     System.out.println("Hello From Team Baeldung"); // @highlight
+ * }
+ * }
+ * 
+ * highlighting a substring
+ * {@snippet :
+ * public void helloBaeldung() {
+ *     System.out.println("Hello From Team Baeldung"); // @highlight substring="println"
+ * }
+ * }
+ * 
+ * highlighting texts on multiple lines
+ * {@snippet : 
+ * public void helloBaeldung() { 
+ *     System.out.println("Hello From Team Baeldung"); // @highlight region substring="println"
+ *     String country = "USA"; 
+ *     System.out.println("Hello From Team " + country); // @end 
+ * } 
+ * }
+ * 
+ */
+
+public class GreetingsHighlightTag {
+    public void helloBaeldung() {
+        System.out.println("Hello From Team Baeldung");
+    }
+
+}

core-java-modules/core-java-documentation/src/main/java/com/baeldung/snippettag/GreetingsInlineSnippet.java

@@ -0,0 +1,17 @@
+package com.baeldung.snippettag;
+
+/**
+ * The code below shows the content of {@code helloBaeldung()} method
+ * {@snippet :
+ * public void helloBaeldung() {
+ *     System.out.println("Hello From Team Baeldung");
+ * }
+ * }
+ */
+
+public class GreetingsInlineSnippet {
+    public void helloBaeldung() {
+        System.out.println("Hello From Team Baeldung");
+    }
+
+}

core-java-modules/core-java-documentation/src/main/java/com/baeldung/snippettag/GreetingsReplaceAndLinkTag.java

@@ -0,0 +1,24 @@
+package com.baeldung.snippettag;
+
+/**
+ * 
+ * Using the replace tag
+ * {@snippet :
+ * public void helloBaeldung() {
+ *     System.out.println("Hello From Team Baeldung"); // @replace regex='".*"' replacement="..."
+ * }
+ * }
+ * Using the link tag
+ * {@snippet :
+ * public void helloBaeldung() {
+ *     System.out.println("Hello From Team Baeldung"); // @link substring="System.out" target="System#out"
+ * }
+ * }
+ *
+ */
+
+public class GreetingsReplaceAndLinkTag {
+    public void helloBaeldung() {
+        System.out.println("Hello From Team Baeldung");
+    }
+}

core-java-modules/core-java-documentation/src/main/java/snippet-files/BinarySearch.java

@@ -0,0 +1,27 @@
+
+public class BinarySearch {
+
+    public int search(int[] list, int item) {
+        int index = Integer.MAX_VALUE;
+        int low = 0;
+        int high = list.length - 1;
+        // @start region="binary"
+        while (low <= high) {
+            int mid = high - low;
+            int guess = list[mid];
+            if (guess == item) {
+                index = mid;
+                break;
+            } else if (guess > item) {
+                low = mid - 1;
+            } else {
+                low = mid + 1;
+            }
+            low++;
+        }
+        // @end region="binary"
+
+        return index;
+    }
+
+}

core-java-modules/core-java-documentation/src/main/java/snippet-files/application.properties

@@ -0,0 +1,4 @@
+# @start region="zone" 
+local.timezone = GMT+1 
+local.zip = 94123 
+# @end region="zone"

core-java-modules/core-java-io-5/.gitignore

@@ -0,0 +1,2 @@
+test-link*
+0.*

core-java-modules/core-java-io-5/README.md

@@ -0,0 +1,8 @@
+## Core Java IO
+
+This module contains articles about core Java input and output (IO)
+
+### Relevant Articles: 
+- [Get File Extension From MIME Type in Java](https://www.baeldung.com/java-mime-type-file-extension)
+- [[<-- Prev]](/core-java-modules/core-java-io-4)
+

core-java-modules/core-java-io-5/pom.xml

@@ -0,0 +1,66 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-io-5</artifactId>
+    <name>core-java-io-5</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <!-- Mime Type Resolution Libraries -->
+        <dependency>
+            <groupId>org.apache.tika</groupId>
+            <artifactId>tika-core</artifactId>
+            <version>${tika.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>net.sf.jmimemagic</groupId>
+            <artifactId>jmimemagic</artifactId>
+            <version>${jmime-magic.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.jodd</groupId>
+            <artifactId>jodd-util</artifactId>
+            <version>${jodd-util.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.j256.simplemagic</groupId>
+            <artifactId>simplemagic</artifactId>
+            <version>${simplemagic.version}</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-io-5</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+        <plugins>
+            <plugin>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>11</source>
+                    <target>11</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <!-- Mime Type Libraries -->
+        <tika.version>2.8.0</tika.version>
+        <jmime-magic.version>0.1.5</jmime-magic.version>
+        <jodd-util.version>6.2.1</jodd-util.version>
+        <simplemagic.version>1.17</simplemagic.version>
+    </properties>
+</project>

core-java-modules/core-java-io-5/src/test/java/com/baeldung/extension/ExtensionFromMimeTypeUnitTest.java

@@ -11,10 +11,8 @@ import java.util.Map;
 import java.util.Set;
 
 import org.apache.tika.mime.MimeTypeException;
-
-import org.junit.Test;
-
 import com.j256.simplemagic.ContentType;
+import org.junit.Test;
 
 public class ExtensionFromMimeTypeUnitTest {
     private static final String IMAGE_JPEG_MIME_TYPE = "image/jpeg";
@@ -37,14 +35,14 @@ public class ExtensionFromMimeTypeUnitTest {
     }
 
     @Test
-    public void whenUsingMimetypesFileTypeMap_thenGetFileExtension() {
+    public void whenUsingSimpleMagic_thenGetFileExtension() {
         List<String> expectedExtensions = Arrays.asList("jpeg", "jpg", "jpe");
         String[] detectedExtensions = ContentType.fromMimeType(IMAGE_JPEG_MIME_TYPE).getFileExtensions();
         assertThat(detectedExtensions).containsExactlyElementsOf(expectedExtensions);
     }
 
     @Test
-    public void whenUsingCustomLogic_thenGetFileExtension() {
+    public void whenUsingCustomMap_thenGetFileExtension() {
         Map<String, Set<String>> mimeExtensionsMap = new HashMap<>();
         List<String> expectedExtensions = Arrays.asList(".jpg", ".jpe", ".jpeg");
         addMimeExtensions(mimeExtensionsMap, "image/jpeg", ".jpg");

core-java-modules/core-java-io-5/src/test/java/com/baeldung/rmlinebreaks/RemoveLinebreaksUnitTest.java

@@ -0,0 +1,72 @@
+package com.baeldung.rmlinebreaks;
+
+import org.junit.jupiter.api.Test;
+
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+
+public class RemoveLinebreaksUnitTest {
+
+    private Path file1Path() throws Exception {
+        return Paths.get(this.getClass().getClassLoader().getResource("multiple-line-1.txt").toURI());
+    }
+
+    private Path file2Path() throws Exception {
+        return Paths.get(this.getClass().getClassLoader().getResource("multiple-line-2.txt").toURI());
+    }
+
+    @Test
+    void whenRemovingLineSeparatorFromFile1_thenGetTheExpectedResult() throws Exception {
+        String content = Files.readString(file1Path(), StandardCharsets.UTF_8);
+
+        String result = content.replace(System.getProperty("line.separator"), "");
+        assertEquals("A, B, C, D, E, F", result);
+    }
+
+    @Test
+    void whenRemovingLineSeparatorFromFile2_thenNotGetTheExpectedResult() throws Exception {
+        String content = Files.readString(file2Path(), StandardCharsets.UTF_8);
+
+        String result = content.replace(System.getProperty("line.separator"), "");
+        assertNotEquals("A, B, C, D, E, F", result); // <-- NOT equals assertion!
+    }
+
+    @Test
+    void whenRemovingAllLinebreaks_thenGetTheExpectedResult() throws Exception {
+        String content1 = Files.readString(file1Path(), StandardCharsets.UTF_8);
+
+        // file contains CRLF
+        String content2 = Files.readString(file2Path(), StandardCharsets.UTF_8);
+
+        String result1 = content1.replace("\r", "").replace("\n", "");
+        String result2 = content2.replace("\r", "").replace("\n", "");
+
+        assertEquals("A, B, C, D, E, F", result1);
+        assertEquals("A, B, C, D, E, F", result2);
+
+        String resultReplaceAll = content2.replaceAll("[\\n\\r]", "");
+        assertEquals("A, B, C, D, E, F", resultReplaceAll);
+
+    }
+
+    @Test
+    void whenUsingReadAllLinesAndJoin_thenGetExpectedResult() throws Exception {
+        List<String> lines1 = Files.readAllLines(file1Path(), StandardCharsets.UTF_8);
+
+        // file contains CRLF
+        List<String> lines2 = Files.readAllLines(file2Path(), StandardCharsets.UTF_8);
+
+        String result1 = String.join("", lines1);
+        String result2 = String.join("", lines2);
+
+        assertEquals("A, B, C, D, E, F", result1);
+        assertEquals("A, B, C, D, E, F", result2);
+    }
+
+}

core-java-modules/core-java-io-5/src/test/resources/multiple-line-1.txt

@@ -0,0 +1,6 @@
+A,
+ B,
+ C,
+ D,
+ E,
+ F

core-java-modules/core-java-io-5/src/test/resources/multiple-line-2.txt

@@ -0,0 +1,4 @@
+A,
 B,
+ C,
+ D,
 E,
+ F

core-java-modules/core-java-io-apis-2/README.md

@@ -7,3 +7,4 @@ This module contains articles about core Java input/output(IO) APIs.
 - [Get the Desktop Path in Java](https://www.baeldung.com/java-desktop-path)
 - [Check if a File Is Empty in Java](https://www.baeldung.com/java-check-file-empty)
 - [Converting Relative to Absolute Paths in Java](https://www.baeldung.com/java-from-relative-to-absolute-paths)
+- [Detect EOF in Java](https://www.baeldung.com/java-file-detect-end-of-file)

core-java-modules/core-java-io/pom.xml

@@ -43,17 +43,6 @@
             <version>${angus-activation.version}</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>org.jodd</groupId>
-            <artifactId>jodd-util</artifactId>
-            <version>${jodd-util.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.j256.simplemagic</groupId>
-            <artifactId>simplemagic</artifactId>
-            <version>${simplemagic.version}</version>
-        </dependency>
-
     </dependencies>
 
     <build>
@@ -153,8 +142,6 @@
         <fscontext.version>4.4.2</fscontext.version>
         <jakarta-activation-api.version>2.1.2</jakarta-activation-api.version>
         <angus-activation.version>2.0.1</angus-activation.version>
-        <jodd-util.version>6.2.1</jodd-util.version>
-        <simplemagic.version>1.17</simplemagic.version>
     </properties>
 
 </project>

core-java-modules/core-java-lang-6/pom.xml

@@ -18,7 +18,11 @@
             <artifactId>mapstruct</artifactId>
             <version>${mapstruct.version}</version>
         </dependency>
-
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
     </dependencies>
     <build>
         <plugins>

core-java-modules/core-java-lang-6/src/main/java/com/baeldung/compareobjects/Address.java

@@ -0,0 +1,47 @@
+package com.baeldung.compareobjects;
+
+import java.util.Objects;
+
+public class Address {
+    private String streetAddress;
+    private String city;
+    private String postalCode;
+
+    public Address(String streetAddress, String city, String postalCode) {
+        this.streetAddress = streetAddress;
+        this.city = city;
+        this.postalCode = postalCode;
+    }
+
+    public String getStreetAddress() {
+        return streetAddress;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public String getPostalCode() {
+        return postalCode;
+    }
+
+    @Override
+    public String toString() {
+        return "Address{" + "streetAddress='" + streetAddress + '\'' + ", city='" + city + '\'' + ", postalCode='" + postalCode + '\'' + '}';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        Address address = (Address) o;
+        return Objects.equals(streetAddress, address.streetAddress) && Objects.equals(city, address.city) && Objects.equals(postalCode, address.postalCode);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(streetAddress, city, postalCode);
+    }
+}

core-java-modules/core-java-lang-6/src/main/java/com/baeldung/compareobjects/Person.java

@@ -0,0 +1,58 @@
+package com.baeldung.compareobjects;
+
+import java.util.List;
+import java.util.Objects;
+
+import org.apache.commons.lang3.builder.DiffExclude;
+
+public class Person {
+    private String firstName;
+    private String lastName;
+    private int age;
+    private List<PhoneNumber> phoneNumbers;
+    @DiffExclude
+    private Address address;
+
+    public Person(String firstName, String lastName, int age, List<PhoneNumber> phoneNumbers, Address address) {
+        this.firstName = firstName;
+        this.lastName = lastName;
+        this.age = age;
+        this.phoneNumbers = phoneNumbers;
+        this.address = address;
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public List<PhoneNumber> getPhoneNumbers() {
+        return phoneNumbers;
+    }
+
+    public Address getAddress() {
+        return address;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        Person person = (Person) o;
+        return age == person.age && Objects.equals(firstName, person.firstName) && Objects.equals(lastName, person.lastName) && Objects.equals(phoneNumbers, person.phoneNumbers) && Objects.equals(address, person.address);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(firstName, lastName, age, phoneNumbers, address);
+    }
+}

core-java-modules/core-java-lang-6/src/main/java/com/baeldung/compareobjects/PersonDiffBuilder.java

@@ -0,0 +1,32 @@
+package com.baeldung.compareobjects;
+
+import org.apache.commons.lang3.builder.DiffBuilder;
+import org.apache.commons.lang3.builder.DiffResult;
+import org.apache.commons.lang3.builder.ToStringStyle;
+
+public class PersonDiffBuilder {
+    public static DiffResult compare(Person first, Person second) {
+        DiffBuilder diffBuilder = new DiffBuilder(first, second, ToStringStyle.DEFAULT_STYLE).append("person", first.getFirstName(), second.getFirstName())
+            .append("lastName", first.getLastName(), second.getLastName())
+            .append("streetAddress", first.getAddress()
+                .getStreetAddress(), second.getAddress()
+                .getStreetAddress())
+            .append("city", first.getAddress()
+                .getCity(), second.getAddress()
+                .getCity())
+            .append("postalCode", first.getAddress()
+                .getPostalCode(), second.getAddress()
+                .getPostalCode())
+            .append("age", first.getAge(), second.getAge());
+
+        for (int i = 0; i < first.getPhoneNumbers()
+            .size(); i++) {
+            diffBuilder.append("phoneNumbers[" + i + "].number", first.getPhoneNumbers()
+                .get(i)
+                .getNumber(), second.getPhoneNumbers()
+                .get(i)
+                .getNumber());
+        }
+        return diffBuilder.build();
+    }
+}

core-java-modules/core-java-lang-6/src/main/java/com/baeldung/compareobjects/PersonReflectionDiffBuilder.java

@@ -0,0 +1,11 @@
+package com.baeldung.compareobjects;
+
+import org.apache.commons.lang3.builder.DiffResult;
+import org.apache.commons.lang3.builder.ReflectionDiffBuilder;
+import org.apache.commons.lang3.builder.ToStringStyle;
+
+public class PersonReflectionDiffBuilder {
+    public static DiffResult compare(Person first, Person second) {
+        return new ReflectionDiffBuilder<>(first, second, ToStringStyle.SHORT_PREFIX_STYLE).build();
+    }
+}

core-java-modules/core-java-lang-6/src/main/java/com/baeldung/compareobjects/PhoneNumber.java

@@ -0,0 +1,43 @@
+package com.baeldung.compareobjects;
+
+import java.util.Objects;
+
+import org.apache.commons.lang3.builder.DiffExclude;
+
+public class PhoneNumber {
+    private String type;
+    private String number;
+
+    public PhoneNumber(String type, String number) {
+        this.type = type;
+        this.number = number;
+    }
+
+    public String getType() {
+        return type;
+    }
+
+    public String getNumber() {
+        return number;
+    }
+
+    @Override
+    public String toString() {
+        return "PhoneNumber{" + "type='" + type + '\'' + ", number='" + number + '\'' + '}';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        PhoneNumber that = (PhoneNumber) o;
+        return Objects.equals(number, that.number);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(number);
+    }
+}

core-java-modules/core-java-lang-6/src/test/java/com/baeldung/compareobjects/PersonDiffBuilderUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.compareobjects;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.commons.lang3.builder.Diff;
+import org.apache.commons.lang3.builder.DiffResult;
+import org.junit.jupiter.api.Test;
+
+public class PersonDiffBuilderUnitTest {
+
+    @Test
+    void givenTwoPeopleDifferent_whenComparingWithDiffBuilder_thenDifferencesFound() {
+        List<PhoneNumber> phoneNumbers1 = new ArrayList<>();
+        phoneNumbers1.add(new PhoneNumber("home", "123-456-7890"));
+        phoneNumbers1.add(new PhoneNumber("work", "987-654-3210"));
+
+        List<PhoneNumber> phoneNumbers2 = new ArrayList<>();
+        phoneNumbers2.add(new PhoneNumber("mobile1", "123-456-7890"));
+        phoneNumbers2.add(new PhoneNumber("mobile2", "987-654-3210"));
+
+        Address address1 = new Address("123 Main St", "London", "12345");
+        Address address2 = new Address("123 Main St", "Paris", "54321");
+
+        Person person1 = new Person("John", "Doe", 30, phoneNumbers1, address1);
+        Person person2 = new Person("Jane", "Smith", 28, phoneNumbers2, address2);
+
+        DiffResult<Person> diff = PersonDiffBuilder.compare(person1, person2);
+        for (Diff<?> d : diff.getDiffs()) {
+            System.out.println(d.getFieldName() + ": " + d.getLeft() + " != " + d.getRight());
+        }
+
+        assertFalse(diff.getDiffs()
+            .isEmpty());
+    }
+}

core-java-modules/core-java-lang-6/src/test/java/com/baeldung/compareobjects/PersonReflectionDiffBuilderUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.compareobjects;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.commons.lang3.builder.Diff;
+import org.apache.commons.lang3.builder.DiffResult;
+import org.junit.jupiter.api.Test;
+
+public class PersonReflectionDiffBuilderUnitTest {
+    @Test
+    void givenTwoPeopleDifferent_whenComparingWithReflectionDiffBuilder_thenDifferencesFound() {
+        List<PhoneNumber> phoneNumbers1 = new ArrayList<>();
+        phoneNumbers1.add(new PhoneNumber("home", "123-456-7890"));
+        phoneNumbers1.add(new PhoneNumber("work", "987-654-3210"));
+
+        List<PhoneNumber> phoneNumbers2 = new ArrayList<>();
+        phoneNumbers2.add(new PhoneNumber("mobile1", "123-456-7890"));
+        phoneNumbers2.add(new PhoneNumber("mobile2", "987-654-3210"));
+
+        Address address1 = new Address("123 Main St", "London", "12345");
+        Address address2 = new Address("123 Main St", "Paris", "54321");
+
+        Person person1 = new Person("John", "Doe", 30, phoneNumbers1, address1);
+        Person person2 = new Person("Jane", "Smith", 28, phoneNumbers2, address2);
+
+        DiffResult<Person> diff = PersonReflectionDiffBuilder.compare(person1, person2);
+        for (Diff<?> d : diff.getDiffs()) {
+            System.out.println(d.getFieldName() + ": " + d.getLeft() + " != " + d.getRight());
+        }
+
+        assertFalse(diff.getDiffs()
+            .isEmpty());
+    }
+}