Merge branch 'master' of github.com:eugenp/tutorials into BAEL-7271-junit-parameterresolver

akka-modules/akka-actors/README.md

@@ -0,0 +1,7 @@
+## Akka HTTP
+
+This module contains articles about Akka actors. 
+
+### Relevant articles:
+
+- [Introduction to Akka Actors in Java](https://www.baeldung.com/akka-actors-java)

akka-modules/akka-actors/pom.xml

@@ -0,0 +1,33 @@
+<?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>akka-actors</artifactId>
+    <name>akka-actors</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>akka-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.typesafe.akka</groupId>
+            <artifactId>akka-actor_${scala.version}</artifactId>
+            <version>${typesafe-akka.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.typesafe.akka</groupId>
+            <artifactId>akka-testkit_${scala.version}</artifactId>
+            <version>${typesafe-akka.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <typesafe-akka.version>2.5.11</typesafe-akka.version>
+    </properties>
+
+</project>

akka-modules/akka-actors/src/main/java/com/baeldung/akkaactors/FirstActor.java

@@ -1,4 +1,4 @@
-package com.baeldung.akka;
+package com.baeldung.akkaactors;
 
 import akka.actor.AbstractActor;
 import akka.actor.Props;

akka-modules/akka-actors/src/main/java/com/baeldung/akkaactors/MyActor.java

@@ -1,4 +1,4 @@
-package com.baeldung.akka;
+package com.baeldung.akkaactors;
 
 import akka.actor.AbstractActor;
 import akka.event.Logging;

akka-modules/akka-actors/src/main/java/com/baeldung/akkaactors/PrinterActor.java

@@ -1,4 +1,4 @@
-package com.baeldung.akka;
+package com.baeldung.akkaactors;
 
 import akka.actor.AbstractActor;
 import akka.actor.Props;

akka-modules/akka-actors/src/main/java/com/baeldung/akkaactors/ReadingActor.java

@@ -1,4 +1,4 @@
-package com.baeldung.akka;
+package com.baeldung.akkaactors;
 
 import akka.actor.AbstractActor;
 import akka.actor.ActorRef;

akka-modules/akka-actors/src/main/java/com/baeldung/akkaactors/WordCounterActor.java

@@ -1,4 +1,4 @@
-package com.baeldung.akka;
+package com.baeldung.akkaactors;
 
 import akka.actor.AbstractActor;
 import akka.event.Logging;

akka-modules/akka-actors/src/test/java/com/baeldung/akkaactors/AkkaActorsUnitTest.java

@@ -1,4 +1,4 @@
-package com.baeldung.akka;
+package com.baeldung.akkaactors;
 
 import akka.actor.ActorRef;
 import akka.actor.ActorSystem;

akka-modules/pom.xml

@@ -14,6 +14,7 @@
     </parent>
 
     <modules>
+        <module>akka-actors</module>
         <module>akka-http</module>
         <module>akka-streams</module>
         <module>spring-akka</module>

apache-httpclient-2/pom.xml

@@ -9,9 +9,8 @@
 
     <parent>
         <groupId>com.baeldung</groupId>
-        <artifactId>parent-java</artifactId>
-        <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../parent-java</relativePath>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
     </parent>
 
     <dependencies>
@@ -74,11 +73,6 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>${maven-compiler-plugin.version}</version>
-                <configuration>
-                    <source>${maven.compiler.source.version}</source>
-                    <target>${maven.compiler.target.version}</target>
-                </configuration>
             </plugin>
         </plugins>
     </build>
@@ -87,8 +81,6 @@
         <assertj.version>3.22.0</assertj.version>
         <mockserver.version>5.11.2</mockserver.version>
         <httpclient5.version>5.2.1</httpclient5.version>
-        <maven.compiler.source.version>11</maven.compiler.source.version>
-        <maven.compiler.target.version>11</maven.compiler.target.version>
         <spring-boot.version>2.1.7.RELEASE</spring-boot.version>
     </properties>
 

apache-httpclient/pom.xml

@@ -9,9 +9,8 @@
 
     <parent>
         <groupId>com.baeldung</groupId>
-        <artifactId>parent-java</artifactId>
-        <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../parent-java</relativePath>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
     </parent>
 
     <dependencies>

apache-kafka-2/pom.xml

@@ -61,9 +61,9 @@
 
     <properties>
         <jna.version>5.7.0</jna.version>
-        <kafka.version>2.8.0</kafka.version>
+        <kafka.version>3.6.1</kafka.version>
         <testcontainers-kafka.version>1.19.3</testcontainers-kafka.version>
-        <testcontainers-jupiter.version>1.15.3</testcontainers-jupiter.version>
+        <testcontainers-jupiter.version>1.19.3</testcontainers-jupiter.version>
         <jackson.databind.version>2.15.2</jackson.databind.version>
     </properties>
 

apache-kafka-2/src/main/java/com/baeldung/kafka/consumer/CustomKafkaListener.java

@@ -0,0 +1,56 @@
+package com.baeldung.kafka.consumer;
+
+import java.io.Closeable;
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.Properties;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.function.Consumer;
+import java.util.logging.Logger;
+
+import org.apache.kafka.clients.consumer.ConsumerConfig;
+import org.apache.kafka.clients.consumer.KafkaConsumer;
+import org.apache.kafka.common.serialization.StringDeserializer;
+
+public class CustomKafkaListener implements Runnable {
+    private static final Logger log = Logger.getLogger(CustomKafkaListener.class.getName());
+    private final String topic;
+    private final KafkaConsumer<String, String> consumer;
+    private Consumer<String> recordConsumer;
+
+
+    public CustomKafkaListener(String topic, KafkaConsumer<String, String> consumer) {
+        this.topic = topic;
+        this.consumer = consumer;
+        this.recordConsumer = record -> log.info("received: " + record);
+    }
+
+    public CustomKafkaListener(String topic, String bootstrapServers) {
+        this(topic, defaultKafkaConsumer(bootstrapServers));
+    }
+
+    private static KafkaConsumer<String, String> defaultKafkaConsumer(String boostrapServers) {
+        Properties props = new Properties();
+        props.setProperty(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, boostrapServers);
+        props.setProperty(ConsumerConfig.GROUP_ID_CONFIG, "test_group_id");
+        props.setProperty(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
+        props.setProperty(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
+        props.setProperty(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
+        return new KafkaConsumer<>(props);
+    }
+
+    public CustomKafkaListener onEach(Consumer<String> newConsumer) {
+        recordConsumer = recordConsumer.andThen(newConsumer);
+        return this;
+    }
+
+    @Override
+    public void run() {
+        consumer.subscribe(Arrays.asList(topic));
+        while (true) {
+            consumer.poll(Duration.ofMillis(100))
+              .forEach(record -> recordConsumer.accept(record.value()));
+        }
+    }
+
+}

apache-kafka-2/src/test/java/com/baeldung/kafka/consumer/CustomKafkaListenerLiveTest.java

@@ -0,0 +1,82 @@
+package com.baeldung.kafka.consumer;
+
+import static java.time.Duration.ofMillis;
+import static java.time.Duration.ofSeconds;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.testcontainers.shaded.org.awaitility.Awaitility.await;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Properties;
+import java.util.concurrent.CompletableFuture;
+
+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.StringSerializer;
+import org.junit.jupiter.api.Test;
+import org.testcontainers.containers.KafkaContainer;
+import org.testcontainers.junit.jupiter.Container;
+import org.testcontainers.junit.jupiter.Testcontainers;
+import org.testcontainers.shaded.org.awaitility.Awaitility;
+import org.testcontainers.utility.DockerImageName;
+
+@Testcontainers
+class CustomKafkaListenerLiveTest {
+
+    @Container
+    private static final KafkaContainer KAFKA_CONTAINER = new KafkaContainer(DockerImageName.parse("confluentinc/cp-kafka:latest"));
+
+    static {
+        Awaitility.setDefaultTimeout(ofSeconds(5L));
+        Awaitility.setDefaultPollInterval(ofMillis(50L));
+    }
+
+    @Test
+    void givenANewCustomKafkaListener_thenConsumesAllMessages() {
+        // given
+        String topic = "baeldung.articles.published";
+        String bootstrapServers = KAFKA_CONTAINER.getBootstrapServers();
+        List<String> consumedMessages = new ArrayList<>();
+
+        // when
+        CustomKafkaListener listener = new CustomKafkaListener(topic, bootstrapServers).onEach(consumedMessages::add);
+        CompletableFuture.runAsync(listener);
+
+        // and
+        publishArticles(topic,
+          "Introduction to Kafka",
+          "Kotlin for Java Developers",
+          "Reactive Spring Boot",
+          "Deploying Spring Boot Applications",
+          "Spring Security"
+        );
+
+        // then
+        await().untilAsserted(() ->
+          assertThat(consumedMessages).containsExactlyInAnyOrder(
+            "Introduction to Kafka",
+            "Kotlin for Java Developers",
+            "Reactive Spring Boot",
+            "Deploying Spring Boot Applications",
+            "Spring Security"
+          ));
+    }
+
+    private void publishArticles(String topic, String... articles) {
+        try (KafkaProducer<String, String> producer = testKafkaProducer()) {
+            Arrays.stream(articles)
+                .map(article -> new ProducerRecord<>(topic, "key-1", article))
+                .forEach(producer::send);
+        }
+    }
+
+    private static KafkaProducer<String, String> testKafkaProducer() {
+        Properties props = new Properties();
+        props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, KAFKA_CONTAINER.getBootstrapServers());
+        props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
+        props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
+        return new KafkaProducer<>(props);
+    }
+}

apache-kafka/pom.xml

@@ -181,6 +181,7 @@
     </build>
 
     <properties>
+        <jackson.version>2.13.4</jackson.version>
         <kafka.version>3.4.0</kafka.version>
         <testcontainers-kafka.version>1.19.3</testcontainers-kafka.version>
         <testcontainers-jupiter.version>1.15.3</testcontainers-jupiter.version>

apache-kafka/src/test/java/com/baeldung/flink/BackupCreatorUnitTest.java

@@ -29,7 +29,7 @@ import java.util.List;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 
-public class BackupCreatorIntegrationTest {
+public class BackupCreatorUnitTest {
     public static ObjectMapper mapper;
 
     @Before

apache-kafka/src/test/java/com/baeldung/flink/WordCapitalizerUnitTest.java

@@ -10,7 +10,7 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.stream.Collectors;
 
-public class WordCapitalizerIntegrationTest {
+public class WordCapitalizerUnitTest {
 
     @Test
     public void givenDataSet_whenExecuteWordCapitalizer_thenReturnCapitalizedWords() throws Exception {

apache-kafka/src/test/java/com/baeldung/kafkastreams/KafkaStreamsLiveTest.java

@@ -21,8 +21,7 @@ import org.junit.Ignore;
 import org.junit.Test;
 
 public class KafkaStreamsLiveTest {
-    private String bootstrapServers = "localhost:9092";
-    private Path stateDirectory;
+    private final String bootstrapServers = "localhost:9092";
 
     @Test
     @Ignore("it needs to have kafka broker running on local")
@@ -44,8 +43,8 @@ public class KafkaStreamsLiveTest {
         
         // Use a temporary directory for storing state, which will be automatically removed after the test.
         try {
-            this.stateDirectory = Files.createTempDirectory("kafka-streams");
-            streamsConfiguration.put(StreamsConfig.STATE_DIR_CONFIG, this.stateDirectory.toAbsolutePath()
+            Path stateDirectory = Files.createTempDirectory("kafka-streams");
+            streamsConfiguration.put(StreamsConfig.STATE_DIR_CONFIG, stateDirectory.toAbsolutePath()
                 .toString());
         } catch (final IOException e) {
             throw new UncheckedIOException("Cannot create temporary directory", e);

asm/README.md

@@ -1,7 +0,0 @@
-## ASM
-
-This module contains articles about ASM
-
-### Relevant Articles:
-
-- [A Guide to Java Bytecode Manipulation with ASM](https://www.baeldung.com/java-asm)

asm/pom.xml

@@ -1,54 +0,0 @@
-<?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>
-    <groupId>com.baeldung.examples</groupId>
-    <artifactId>asm</artifactId>
-    <version>1.0</version>
-    <name>asm</name>
-    <packaging>jar</packaging>
-
-    <parent>
-        <groupId>com.baeldung</groupId>
-        <artifactId>parent-modules</artifactId>
-        <version>1.0.0-SNAPSHOT</version>
-    </parent>
-
-    <dependencies>
-        <dependency>
-            <groupId>org.ow2.asm</groupId>
-            <artifactId>asm</artifactId>
-            <version>${asm.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.ow2.asm</groupId>
-            <artifactId>asm-util</artifactId>
-            <version>${asm.version}</version>
-        </dependency>
-    </dependencies>
-
-    <build>
-        <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-jar-plugin</artifactId>
-                <version>${maven-jar-plugin.version}</version>
-                <configuration>
-                    <archive>
-                        <manifestEntries>
-                            <Premain-Class>
-                                com.baeldung.examples.asm.instrumentation.Premain
-                            </Premain-Class>
-                        </manifestEntries>
-                    </archive>
-                </configuration>
-            </plugin>
-        </plugins>
-    </build>
-
-    <properties>
-        <asm.version>5.2</asm.version>
-    </properties>
-
-</project>

aws-modules/aws-dynamodb/pom.xml

@@ -40,22 +40,6 @@
 
     <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>

aws-modules/aws-miscellaneous/pom.xml

@@ -34,22 +34,6 @@
 
     <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>

aws-modules/aws-reactive/pom.xml

@@ -63,6 +63,7 @@
         <dependency>
             <groupId>io.projectreactor</groupId>
             <artifactId>reactor-test</artifactId>
+            <version>${reactor.version}</version>
             <scope>test</scope>
         </dependency>
         <dependency>
@@ -93,6 +94,7 @@
     <properties>
         <spring.version>2.2.1.RELEASE</spring.version>
         <awssdk.version>2.17.283</awssdk.version>
+        <reactor.version>3.6.0</reactor.version>
     </properties>
 
 </project>

aws-modules/aws-s3/pom.xml

@@ -39,27 +39,6 @@
         </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>
-        </plugins>
-    </build>
-
     <properties>
         <aws.java.sdk.version>2.20.52</aws.java.sdk.version>
         <commons-codec-version>1.10.L001</commons-codec-version>

checker-framework/pom.xml

@@ -31,8 +31,8 @@
     <build>
         <plugins>
             <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>${maven-compiler-plugin.version}</version>
                 <configuration>
                     <fork>true</fork>
                     <compilerArgument>-Xlint:all</compilerArgument>

core-java-modules/core-java-10/pom.xml

@@ -26,7 +26,6 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>${maven-compiler-plugin.version}</version>
                 <configuration>
                     <source>${maven.compiler.source.version}</source>
                     <target>${maven.compiler.target.version}</target>

core-java-modules/core-java-11/pom.xml

@@ -48,7 +48,6 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>${maven-compiler-plugin.version}</version>
                 <configuration>
                     <source>${maven.compiler.source.version}</source>
                     <target>${maven.compiler.target.version}</target>

core-java-modules/core-java-14/pom.xml

@@ -27,7 +27,6 @@
             <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>

core-java-modules/core-java-16/pom.xml

@@ -27,7 +27,6 @@
             <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>

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

@@ -19,7 +19,6 @@
             <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>

core-java-modules/core-java-20/README.md

@@ -1,3 +1,4 @@
 ## Relevant Articles
 - [Scoped Values in Java 20](https://www.baeldung.com/java-20-scoped-values)
 - [How to Read Zip Files Entries With Java](https://www.baeldung.com/java-read-zip-files)
+- [Deserializing JSON to Java Record using Gson](https://www.baeldung.com/java-json-deserialize-record-gson)

core-java-modules/core-java-8-datetime-2/src/main/java/com/baeldung/localdatetoiso/LocalDateToISO.java

@@ -0,0 +1,44 @@
+package com.baeldung.localdatetoiso;
+
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
+import java.time.LocalDate;
+import java.time.ZoneOffset;
+import java.time.format.DateTimeFormatter;
+import java.util.Date;
+
+import org.apache.commons.lang3.time.DateFormatUtils;
+
+import org.joda.time.DateTime;
+import org.joda.time.DateTimeZone;
+import org.joda.time.format.DateTimeFormat;
+import org.joda.time.format.ISODateTimeFormat;
+
+import org.apache.commons.lang3.time.FastDateFormat;
+
+public class LocalDateToISO {
+    public String formatUsingDateTimeFormatter(LocalDate localDate) {
+        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSX");
+        String formattedDate = localDate.atStartOfDay().atOffset(ZoneOffset.UTC).format(formatter);
+        return formattedDate;
+    }
+
+    public String formatUsingSimpleDateFormat(LocalDate date) {
+        Date utilDate = Date.from(date.atStartOfDay(ZoneOffset.UTC).toInstant());
+        DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSX");
+        String formattedDate = dateFormat.format(utilDate);
+        return formattedDate;
+    }
+
+    public String formatUsingJodaTime(org.joda.time.LocalDate localDate) {
+        org.joda.time.format.DateTimeFormatter formatter = ISODateTimeFormat.dateTime();
+        return formatter.print(localDate.toDateTimeAtStartOfDay(DateTimeZone.UTC));
+    }
+
+     public String formatUsingApacheCommonsLang(LocalDate localDate) {
+        Date date = Date.from(localDate.atStartOfDay().toInstant(ZoneOffset.UTC));
+        String formattedDate = FastDateFormat.getInstance("yyyy-MM-dd'T'HH:mm:ss.sss'Z'", TimeZone.getTimeZone("UTC"))
+            .format(date);
+        return formattedDate;
+    }
+}

core-java-modules/core-java-8-datetime-2/src/main/java/com/baeldung/monthintervalbetweentwodates/MonthInterval.java

@@ -0,0 +1,44 @@
+package com.baeldung.monthintervalbetweentwodates;
+
+import java.util.Calendar;
+import java.util.Date;
+
+public class MonthInterval {
+
+    public int monthsBetween(Date startDate, Date endDate) {
+        if (startDate == null || endDate == null) {
+            throw new IllegalArgumentException("Both startDate and endDate must be provided");
+        }
+        
+        Calendar startCalendar = Calendar.getInstance();
+        startCalendar.setTime(startDate);
+        int startDateTotalMonths = 12 * startCalendar.get(Calendar.YEAR) + startCalendar.get(Calendar.MONTH);
+        
+        Calendar endCalendar = Calendar.getInstance();
+        endCalendar.setTime(endDate);
+        int endDateTotalMonths = 12 * endCalendar.get(Calendar.YEAR) + endCalendar.get(Calendar.MONTH);
+        
+        return endDateTotalMonths - startDateTotalMonths;
+    }
+
+    public int monthsBetweenWithDayValue(Date startDate, Date endDate) {
+        if (startDate == null || endDate == null) {
+            throw new IllegalArgumentException("Both startDate and endDate must be provided");
+        }
+        
+        Calendar startCalendar = Calendar.getInstance();
+        startCalendar.setTime(startDate);
+        
+        int startDateDayOfMonth = startCalendar.get(Calendar.DAY_OF_MONTH);
+        int startDateTotalMonths = 12 * startCalendar.get(Calendar.YEAR) + startCalendar.get(Calendar.MONTH);
+        
+        Calendar endCalendar = Calendar.getInstance();
+        endCalendar.setTime(endDate);
+        
+        int endDateDayOfMonth = endCalendar.get(Calendar.DAY_OF_MONTH);
+        int endDateTotalMonths = 12 * endCalendar.get(Calendar.YEAR) + endCalendar.get(Calendar.MONTH);
+
+        return (startDateDayOfMonth > endDateDayOfMonth) ? (endDateTotalMonths - startDateTotalMonths) - 1 : (endDateTotalMonths - startDateTotalMonths);
+    }
+
+}

core-java-modules/core-java-8-datetime-2/src/test/java/com/baeldung/localdatetoiso/LocalDateToISOUnitTest.java

@@ -0,0 +1,48 @@
+package com.baeldung.localdatetoiso;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+import java.time.LocalDate;
+
+public class LocalDateToISOUnitTest {
+    @Test
+    void givenLocalDate_whenUsingDateTimeFormatter_thenISOFormat(){
+        LocalDateToISO localDateToISO = new LocalDateToISO();
+        LocalDate localDate = LocalDate.of(2023, 11, 6);
+
+        String expected = "2023-11-06T00:00:00.000Z";
+        String actual = localDateToISO.formatUsingDateTimeFormatter(localDate);
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    void givenLocalDate_whenUsingSimpleDateFormat_thenISOFormat(){
+        LocalDateToISO localDateToISO = new LocalDateToISO();
+        LocalDate localDate = LocalDate.of(2023, 11, 6);
+
+        String expected = "2023-11-06T00:00:00.000Z";
+        String actual = localDateToISO.formatUsingSimpleDateFormat(localDate);
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    void givenLocalDate_whenUsingJodaTime_thenISOFormat() {
+        LocalDateToISO localDateToISO = new LocalDateToISO();
+        org.joda.time.LocalDate localDate = new org.joda.time.LocalDate(2023, 11, 6);
+
+        String expected = "2023-11-06T00:00:00.000Z";
+        String actual = localDateToISO.formatUsingJodaTime(localDate);
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    void givenLocalDate_whenUsingApacheCommonsLang_thenISOFormat() {
+        LocalDateToISO localDateToISO = new LocalDateToISO();
+        LocalDate localDate = LocalDate.of(2023, 11, 6);
+
+        String expected = "2023-11-06T00:00:00.000Z";
+        String actual = localDateToISO.formatUsingApacheCommonsLang(localDate);
+        assertEquals(expected, actual);
+    }
+}

core-java-modules/core-java-8-datetime-2/src/test/java/com/baeldung/monthintervalbetweentwodates/MonthIntervalUnitTest.java

@@ -0,0 +1,93 @@
+package com.baeldung.monthintervalbetweentwodates;
+
+import org.joda.time.DateTime;
+import org.joda.time.Months;
+import org.junit.jupiter.api.Test;
+
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.time.LocalDate;
+import java.time.Period;
+import java.time.YearMonth;
+import java.time.temporal.ChronoUnit;
+import java.util.Date;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class MonthIntervalUnitTest {
+
+    @Test
+    void givenTwoDates_whenCalculatingMonthsBetweenUsingJodaTime_thenReturnMonthsDifference() {
+        DateTime firstDate = new DateTime(2023, 5, 25, 0, 0);
+        DateTime secondDate = new DateTime(2023, 11, 23, 0, 0);
+
+        int monthsBetween = Months.monthsBetween(firstDate, secondDate)
+          .getMonths();
+        assertEquals(5, monthsBetween);
+    }
+
+    @Test
+    void givenTwoDates_whenCalculatingMonthsBetweenUsingJodaTimeSetTimeToFirstDayOfMonth_thenReturnMonthsDifference() {
+        DateTime firstDate = new DateTime(2023, 5, 25, 0, 0).withDayOfMonth(1);
+        DateTime secondDate = new DateTime(2023, 11, 23, 0, 0).withDayOfMonth(1);
+
+        int monthsBetween = Months.monthsBetween(firstDate, secondDate)
+          .getMonths();
+        assertEquals(6, monthsBetween);
+    }
+
+    @Test
+    void givenTwoDates_whenCalculatingMonthsBetweenUsingPeriodClass_thenReturnMonthsDifference() {
+        Period diff = Period.between(LocalDate.parse("2023-05-25"), LocalDate.parse("2023-11-23"));
+        assertEquals(5, diff.getMonths());
+    }
+
+    @Test
+    void givenTwoDates_whenCalculatingMonthsBetweenUsingPeriodClassAndAdjsutingDatesToFirstDayOfTheMonth_thenReturnMonthsDifference() {
+        Period diff = Period.between(LocalDate.parse("2023-05-25")
+          .withDayOfMonth(1), LocalDate.parse("2023-11-23")
+          .withDayOfMonth(1));
+        assertEquals(6, diff.getMonths());
+    }
+
+    @Test
+    void givenTwoDates_whenCalculatingMonthsBetweenUsingChronoUnitAndYearMonth_thenReturnMonthsDifference() {
+        long diff = ChronoUnit.MONTHS.between(YearMonth.from(LocalDate.parse("2023-05-25")), LocalDate.parse("2023-11-23"));
+        assertEquals(6, diff);
+    }
+
+    @Test
+    void givenTwoDates_whenCalculatingMonthsBetweenUsingChronoUnitEnum_thenReturnMonthsDifference() {
+        long monthsBetween = ChronoUnit.MONTHS.between(LocalDate.parse("2023-05-25"), LocalDate.parse("2023-11-23"));
+        assertEquals(5, monthsBetween);
+    }
+
+    @Test
+    void givenTwoDates_whenCalculatingMonthsBetweenUsingChronoUnitEnumdSetTimeToFirstDayOfMonth_thenReturnMonthsDifference() {
+        long monthsBetween = ChronoUnit.MONTHS.between(LocalDate.parse("2023-05-25")
+          .withDayOfMonth(1), LocalDate.parse("2023-11-23")
+          .withDayOfMonth(1));
+        assertEquals(6, monthsBetween);
+    }
+
+    @Test
+    void givenTwoDates_whenCalculatingMonthsBetweenUsingLegacyDateApi_thenReturnMonthsDifference() throws ParseException {
+        MonthInterval monthDifference = new MonthInterval();
+        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
+        Date startDate = sdf.parse("2016-05-31");
+        Date endDate = sdf.parse("2016-11-30");
+        int monthsBetween = monthDifference.monthsBetween(startDate, endDate);
+        assertEquals(6, monthsBetween);
+
+    }
+
+    @Test
+    void givenTwoDates_whenCalculatingMonthsBetweenUsingLegacyDateApiDayValueConsidered_thenReturnMonthsDifference() throws ParseException {
+        MonthInterval monthDifference = new MonthInterval();
+        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
+        Date startDate = sdf.parse("2016-05-31");
+        Date endDate = sdf.parse("2016-11-28");
+        int monthsBetween = monthDifference.monthsBetweenWithDayValue(startDate, endDate);
+        assertEquals(5, monthsBetween);
+    }
+}

core-java-modules/core-java-9/pom.xml

@@ -59,7 +59,6 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>${maven-compiler-plugin.version}</version>
                 <configuration>
                     <source>${maven.compiler.source}</source>
                     <target>${maven.compiler.target}</target>

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

@@ -11,3 +11,4 @@ This module contains articles about arrays conversion in Java
 - [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)
+- [How to Convert Byte Array to Char Array](https://www.baeldung.com/java-convert-byte-array-char)

core-java-modules/core-java-collections-5/src/test/java/com/baeldung/iteratorvsforloop/IteratorForLoopUnitTest.java

@@ -0,0 +1,129 @@
+package com.baeldung.iteratorvsforloop;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.ConcurrentModificationException;
+import java.util.List;
+import java.util.Iterator;
+import java.util.Collections;
+import java.util.ListIterator;
+
+public class IteratorForLoopUnitTest {
+
+    @Test
+    public void givenEmptyCollection_whenUsingForLoop_thenNoElementsAreIterated() {
+        List<String> names = Collections.emptyList();
+        StringBuilder stringBuilder = new StringBuilder();
+
+        for (int i = 0; i < names.size(); i++) {
+            stringBuilder.append(names.get(i));
+        }
+
+        assertEquals("", stringBuilder.toString());
+    }
+
+    @Test
+    public void givenEmptyCollection_whenUsingIterator_thenNoElementsAreIterated() {
+        List<String> names = Collections.emptyList();
+        StringBuilder stringBuilder = new StringBuilder();
+
+        Iterator<String> iterator = names.iterator();
+        while (iterator.hasNext()) {
+            stringBuilder.append(iterator.next());
+        }
+
+        assertEquals("", stringBuilder.toString());
+    }
+
+
+    @Test
+    public void givenCollectionWithElements_whenUsingForLoop_thenAllElementsAreIterated() {
+        List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
+        StringBuilder stringBuilder = new StringBuilder();
+
+        for (int i = 0; i < names.size(); i++) {
+            stringBuilder.append(names.get(i));
+        }
+
+        assertEquals("AliceBobCharlie", stringBuilder.toString());
+    }
+
+    @Test
+    public void givenCollectionWithElements_whenUsingIterator_thenAllElementsAreIterated() {
+        List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
+        StringBuilder stringBuilder = new StringBuilder();
+
+        Iterator<String> iterator = names.iterator();
+        while (iterator.hasNext()) {
+            stringBuilder.append(iterator.next());
+        }
+
+        assertEquals("AliceBobCharlie", stringBuilder.toString());
+    }
+
+    @Test
+    public void givenCollectionWithElements_whenUsingForLoop_thenAllElementsAreIteratedReverseOrder() {
+        List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
+        StringBuilder stringBuilder = new StringBuilder();
+
+        for (int i = names.size() - 1; i >= 0; i--) {
+            stringBuilder.append(names.get(i));
+        }
+
+        assertEquals("CharlieBobAlice", stringBuilder.toString());
+    }
+
+    @Test
+    public void givenCollectionWithElements_whenUsingListIterator_thenAllElementsAreIteratedInReverseOrder() {
+        List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
+        StringBuilder stringBuilder = new StringBuilder();
+
+        ListIterator<String> listIterator = names.listIterator(names.size());
+        while (listIterator.hasPrevious()) {
+            stringBuilder.append(listIterator.previous());
+        }
+
+        assertEquals("CharlieBobAlice", stringBuilder.toString());
+    }
+
+    @Test
+    public void givenCollectionWithElements_whenRemovingElementDuringForLoopIteration_thenConcurrentModificationExceptionIsThrown() {
+        List<String> names = new ArrayList<>(List.of("Alice", "Bob", "Charlie"));
+
+        assertThrows(ConcurrentModificationException.class, () -> {
+            for (String name : names) {
+                names.remove("Bob");
+            }
+        });
+    }
+
+    @Test
+    public void givenCollectionWithElements_whenRemovingElementUsingIterator_thenElementIsRemovedSafely() {
+        List<String> names = new ArrayList<>(Arrays.asList("Alice", "Bob", "Charlie"));
+        Iterator<String> iterator = names.iterator();
+
+        while (iterator.hasNext()) {
+            String name = iterator.next();
+            if (name.equals("Bob")) {
+                iterator.remove();
+            }
+        }
+        List<String> expected = Arrays.asList("Alice", "Charlie");
+        assertIterableEquals(expected, names);
+    }
+
+    @Test
+    public void givenCollectionWithElements_whenModifyingElementToLowerCaseDuringForLoopIteration_thenElementsAreModifiedToLowerCase() {
+        List<String> names = new ArrayList<>(List.of("Alice", "Bob", "Charlie"));
+
+        for (int i = 0; i < names.size(); i++) {
+            names.set(i, names.get(i).toLowerCase());
+        }
+
+        List<String> expected = Arrays.asList("alice","bob", "charlie");
+        assertIterableEquals(expected, names);
+    }
+}

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

@@ -13,4 +13,20 @@
         <version>0.0.1-SNAPSHOT</version>
     </parent>
 
+    <dependencies>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>io.vavr</groupId>
+            <artifactId>vavr</artifactId>
+            <version>${vavr.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <vavr.version>0.10.4</vavr.version>
+    </properties>
 </project>

core-java-modules/core-java-collections-list-6/src/main/java/com/baeldung/sorting/SortingBasedOnAnotherList.java

@@ -0,0 +1,52 @@
+package com.baeldung.sorting;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import com.google.common.collect.Ordering;
+
+public class SortingBasedOnAnotherList {
+    static List<String> sortUsingForLoop(List<String> listToSort, List<String> listWithOrder) {
+        List<String> sortedList = new ArrayList<>();
+        for(String element: listWithOrder) {
+            if(listToSort.contains(element)) {
+                sortedList.add(element);
+            }
+        }
+        return sortedList;
+    }
+
+    static void sortUsingComparator(List<String> listToSort, List<String> listWithOrder) {
+        listToSort.sort(Comparator.comparingInt(listWithOrder::indexOf));
+    }
+
+    static void sortUsingStreamAPI(List<String> listToSort, List<String> listWithOrder) {
+        Map<String,Integer> indicesMap = listWithOrder.stream().collect(Collectors.toMap(e->e, listWithOrder::indexOf));
+        listToSort.sort(Comparator.comparingInt(indicesMap::get));
+    }
+
+    static void sortUsingMap(List<String> listToSort, List<String> listWithOrder) {
+        Map<String, Integer> orderedIndicesMap = new HashMap<>();
+        for(int i = 0; i < listWithOrder.size(); i++) {
+            orderedIndicesMap.put(listWithOrder.get(i), i);
+        }
+        listToSort.sort(Comparator.comparingInt(orderedIndicesMap::get));
+    }
+
+    static List<String> sortUsingGuava(List<String> listToSort, List<String> listWithOrder) {
+        Ordering<String> explicitOrdering = Ordering.explicit(listWithOrder);
+        List<String> sortedList = explicitOrdering.sortedCopy(listToSort);
+        return sortedList;
+    }
+
+    static List<String> sortUsingVavr(List<String> listToSort, List<String> listWithOrder) {
+        io.vavr.collection.List<String> listWithOrderedElements = io.vavr.collection.List.ofAll(listWithOrder);
+        io.vavr.collection.List<String> listToSortElements = io.vavr.collection.List.ofAll(listToSort);
+        io.vavr.collection.List<String> sortedList = listToSortElements.sortBy(listWithOrderedElements::indexOf);
+        return sortedList.asJava();
+    }
+}

core-java-modules/core-java-collections-list-6/src/test/java/com/baeldung/sorting/SortingBasedOnAnotherListUnitTest.java

@@ -0,0 +1,70 @@
+package com.baeldung.sorting;
+
+import static com.baeldung.sorting.SortingBasedOnAnotherList.sortUsingComparator;
+import static com.baeldung.sorting.SortingBasedOnAnotherList.sortUsingForLoop;
+import static com.baeldung.sorting.SortingBasedOnAnotherList.sortUsingGuava;
+import static com.baeldung.sorting.SortingBasedOnAnotherList.sortUsingMap;
+import static com.baeldung.sorting.SortingBasedOnAnotherList.sortUsingStreamAPI;
+import static com.baeldung.sorting.SortingBasedOnAnotherList.sortUsingVavr;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+public class SortingBasedOnAnotherListUnitTest {
+    @Test
+    public void givenTwoList_whenUsingForLoop_thenSort() {
+        List<String> listWithOrder = Arrays.asList("Burger", "Coke", "Fries", "Pizza");
+        List<String> listToSort = Arrays.asList("Pizza", "Burger", "Fries", "Coke");
+        sortUsingForLoop(listToSort, listWithOrder);
+        List<String> expectedSortedList = Arrays.asList("Burger", "Coke", "Fries", "Pizza");
+        assertEquals(expectedSortedList, listWithOrder);
+    }
+
+    @Test
+    public void givenTwoList_whenUsingComparator_thenSort() {
+        List<String> listWithOrder = Arrays.asList("Burger", "Coke", "Fries", "Pizza");
+        List<String> listToSort = Arrays.asList("Pizza", "Burger", "Fries", "Coke");
+        sortUsingComparator(listToSort, listWithOrder);
+        List<String> expectedSortedList = Arrays.asList("Burger", "Coke", "Fries", "Pizza");
+        assertEquals(expectedSortedList, listToSort);
+    }
+
+    @Test
+    public void givenTwoList_whenUsingStreamAPI_thenSort() {
+        List<String> listWithOrder = Arrays.asList("Burger", "Coke", "Fries", "Pizza");
+        List<String> listToSort = Arrays.asList("Pizza", "Burger", "Fries", "Coke");
+        sortUsingStreamAPI(listToSort, listWithOrder);
+        List<String> expectedSortedList = Arrays.asList("Burger", "Coke", "Fries", "Pizza");
+        assertEquals(expectedSortedList, listToSort);
+    }
+
+    @Test
+    public void givenTwoList_whenUsingMap_thenSort() {
+        List<String> listWithOrder = Arrays.asList("Burger", "Coke", "Fries", "Pizza");
+        List<String> listToSort = Arrays.asList("Pizza", "Burger", "Fries", "Coke");
+        sortUsingMap(listToSort, listWithOrder);
+        List<String> expectedSortedList = Arrays.asList("Burger", "Coke", "Fries", "Pizza");
+        assertEquals(expectedSortedList, listToSort);
+    }
+
+    @Test
+    public void givenTwoList_whenUsingGuavaExplicit_thenSort() {
+        List<String> listWithOrder = Arrays.asList("Burger", "Coke", "Fries", "Pizza");
+        List<String> listToSort = Arrays.asList("Pizza", "Burger", "Fries", "Coke");
+        sortUsingGuava(listToSort, listWithOrder);
+        List<String> expectedSortedList = Arrays.asList("Burger", "Coke", "Fries", "Pizza");
+        assertEquals(expectedSortedList, listWithOrder);
+    }
+
+    @Test
+    public void givenTwoList_whenUsingVavr_thenSort() {
+        List<String> listWithOrder = Arrays.asList("Burger", "Coke", "Fries", "Pizza");
+        List<String> listToSort = Arrays.asList("Pizza", "Burger", "Fries", "Coke");
+        sortUsingVavr(listToSort, listWithOrder);
+        List<String> expectedSortedList = Arrays.asList("Burger", "Coke", "Fries", "Pizza");
+        assertEquals(expectedSortedList, listWithOrder);
+    }
+}

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

@@ -10,4 +10,5 @@ This module contains articles about Map data structures in Java.
 - [Java HashMap Load Factor](https://www.baeldung.com/java-hashmap-load-factor)
 - [Converting Java Properties to HashMap](https://www.baeldung.com/java-convert-properties-to-hashmap)
 - [Get Values and Keys as ArrayList From a HashMap](https://www.baeldung.com/java-values-keys-arraylists-hashmap)
-- More articles: [[<-- prev]](/core-java-modules/core-java-collections-maps-2)
+- [Remove Duplicate Values From HashMap in Java](https://www.baeldung.com/java-hashmap-delete-duplicates)
+- More articles: [[<-- prev]](/core-java-modules/core-java-collections-maps-2)[[next -->]](/core-java-modules/core-java-collections-maps-4)

core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/removeduplicate/RemoveDuplicateValuesUnitTest.java

@@ -1,4 +1,4 @@
-package com.baeldung.map.removeuplicate;
+package com.baeldung.map.removeduplicate;
 
 import static java.util.stream.Collectors.toMap;
 import static org.assertj.core.api.Assertions.assertThat;

core-java-modules/core-java-collections-maps-4/README.md

@@ -9,3 +9,4 @@ This module contains articles about Map data structures in Java.
 - [Difference Between Map and HashMap in Java](https://www.baeldung.com/java-map-vs-hashmap)
 - [How to Create a New Entry in a Map](https://www.baeldung.com/java-map-new-entry)
 - [Difference Between Map and MultivaluedMap in Java](https://www.baeldung.com/java-map-vs-multivaluedmap)
+- More articles: [[<-- prev]](/core-java-modules/core-java-collections-maps-3)[[next -->]](/core-java-modules/core-java-collections-maps-5)

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

@@ -10,4 +10,5 @@
 - [How to Invert a Map in Java](https://www.baeldung.com/java-invert-map)
 - [Implementing a Map with Multiple Keys in Java](https://www.baeldung.com/java-multiple-keys-map)
 - [Difference Between Map.ofEntries() and Map.of()](https://www.baeldung.com/map-ofentries-and-map-of)
-- More articles: [[<-- prev]](../core-java-collections-maps-4)
+- More articles: [[<-- prev]](/core-java-modules/core-java-collections-maps-4)[[next -->]](/core-java-modules/core-java-collections-maps-6)
+

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

@@ -7,6 +7,7 @@
 - [Converting JsonNode Object to Map](https://www.baeldung.com/jackson-jsonnode-map)
 - [How to Modify a Key in a HashMap?](https://www.baeldung.com/java-hashmap-modify-key)
 - [Converting String or String Array to Map in Java](https://www.baeldung.com/java-convert-string-to-map)
-- [Remove Duplicate Values From HashMap in Java](https://www.baeldung.com/java-hashmap-delete-duplicates)
 - [Sorting Java Map in Descending Order](https://www.baeldung.com/java-sort-map-descending)
 - [Convert HashMap.toString() to HashMap in Java](https://www.baeldung.com/hashmap-from-tostring)
+- More articles: [[<-- prev]](/core-java-modules/core-java-collections-maps-5)[[next -->]](/core-java-modules/core-java-collections-maps-7)
+

core-java-modules/core-java-concurrency-2/README.md

@@ -7,3 +7,4 @@
 - [Testing Multi-Threaded Code in Java](https://www.baeldung.com/java-testing-multithreaded)
 - [How to Check if All Runnables Are Done](https://www.baeldung.com/java-runnables-check-status)
 - [Parallelize for Loop in Java](https://www.baeldung.com/java-for-loop-parallel)
+- [How to Effectively Unit Test CompletableFuture](https://www.baeldung.com/java-completablefuture-unit-test)

core-java-modules/core-java-concurrency-advanced-5/src/main/java/com/baeldung/callback/completablefuture/CompletableFutureCallbackExample.java

@@ -0,0 +1,30 @@
+package com.baeldung.callback.completablefuture;
+
+import java.util.concurrent.CompletableFuture;
+
+public class CompletableFutureCallbackExample {
+    public static void main(String[] args) {
+        CompletableFuture<String> completableFuture = new CompletableFuture<>();
+        Runnable runnable = downloadFile(completableFuture);
+        completableFuture.whenComplete((res, error) -> {
+            if (error != null) {
+                // handle the exception scenario
+            } else if (res != null) {
+                // send data to DB
+            }
+        });
+        new Thread(runnable).start();
+    }
+
+    private static Runnable downloadFile(CompletableFuture<String> completableFuture) {
+        return () -> {
+            try {
+                //logic to download file
+                Thread.sleep(5000);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            completableFuture.complete("pic.jpg");
+        };
+    }
+}

core-java-modules/core-java-concurrency-advanced-5/src/main/java/com/baeldung/callback/listenablefuture/ListenableFutureCallbackExample.java

@@ -0,0 +1,42 @@
+package com.baeldung.callback.listenablefuture;
+
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import com.google.common.util.concurrent.FutureCallback;
+import com.google.common.util.concurrent.Futures;
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.ListeningExecutorService;
+import com.google.common.util.concurrent.MoreExecutors;
+
+
+public class ListenableFutureCallbackExample {
+    public static void main(String[] args) {
+
+        ExecutorService executorService = Executors.newFixedThreadPool(1);
+        ListeningExecutorService pool = MoreExecutors.listeningDecorator(executorService);
+        ListenableFuture<String> listenableFuture = pool.submit(downloadFile());
+
+        Futures.addCallback(listenableFuture, new FutureCallback<String>() {
+            @Override
+            public void onSuccess(String result) {
+                // code to push fileName to DB
+            }
+
+            @Override
+            public void onFailure(Throwable throwable) {
+                // code to take appropriate action when there is an error
+            }
+        }, executorService);
+    }
+
+    private static Callable<String> downloadFile() {
+        return () -> {
+            // Mimicking the downloading of a file by adding a sleep call
+            Thread.sleep(5000);
+            return "pic.jpg";
+        };
+    }
+
+}

core-java-modules/core-java-concurrency-basic-3/src/main/java/com/baeldung/concurrent/executorservice/ExecuteExample.java

@@ -0,0 +1,24 @@
+package com.baeldung.concurrent.executorservice;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class ExecuteExample {
+    public static void main(String[] args) {
+        ExecutorService executorService = Executors.newFixedThreadPool(2);
+        // Task using Runnable
+        Runnable task = () -> {
+            int[] numbers = { 1, 2, 3, 4, 5 };
+            int sum = 0;
+            for (int num : numbers) {
+                sum += num;
+            }
+            System.out.println("Sum calculated using execute:" + sum);
+        };
+        // Submit the task using execute
+        executorService.execute(task);
+        executorService.shutdown();
+
+    }
+
+}

core-java-modules/core-java-concurrency-basic-3/src/main/java/com/baeldung/concurrent/executorservice/SubmitExample.java

@@ -0,0 +1,31 @@
+package com.baeldung.concurrent.executorservice;
+
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+public class SubmitExample {
+    public static void main(String[] args) {
+        ExecutorService executorService = Executors.newFixedThreadPool(2);
+        Callable<Integer> task = () -> {
+            int[] numbers = { 1, 2, 3, 4, 5 };
+            int sum = 0;
+            for (int num : numbers) {
+                sum += num;
+            }
+            return sum;
+        };
+        // Submit the task and obtain a Future
+        Future<Integer> result = executorService.submit(task);
+        try {
+            // Get the result
+            int sum = result.get();
+            System.out.println("Sum calculated using submit:" + sum);
+        } catch (InterruptedException | ExecutionException e) {
+            e.printStackTrace();
+        }
+        executorService.shutdown();
+    }
+}

core-java-modules/core-java-function/src/main/java/com/baeldung/lazylambda/LambdaSupplier.java

@@ -0,0 +1,16 @@
+package com.baeldung.lazylambda;
+
+import java.util.function.Supplier;
+
+public class LambdaSupplier<T> {
+
+    protected final Supplier<T> expensiveData;
+
+    public LambdaSupplier(Supplier<T> expensiveData) {
+        this.expensiveData = expensiveData;
+    }
+
+    public T getData() {
+        return expensiveData.get();
+    }
+}

core-java-modules/core-java-function/src/main/java/com/baeldung/lazylambda/LazyLambdaSupplier.java

@@ -0,0 +1,21 @@
+package com.baeldung.lazylambda;
+
+import java.util.function.Supplier;
+
+public class LazyLambdaSupplier<T> extends LambdaSupplier<T> {
+
+    private T data;
+
+    public LazyLambdaSupplier(Supplier<T> expensiveData) {
+        super(expensiveData);
+    }
+
+    @Override
+    public T getData() {
+        if (data != null) {
+            return data;
+        }
+        return data = expensiveData.get();
+    }
+
+}

core-java-modules/core-java-function/src/main/java/com/baeldung/lazylambda/LazyLambdaThreadSafeSupplier.java

@@ -0,0 +1,26 @@
+package com.baeldung.lazylambda;
+
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Supplier;
+
+public class LazyLambdaThreadSafeSupplier<T> extends LambdaSupplier<T> {
+
+    private final AtomicReference<T> data;
+
+    public LazyLambdaThreadSafeSupplier(Supplier<T> expensiveData) {
+        super(expensiveData);
+        data = new AtomicReference<>();
+    }
+
+    public T getData() {
+        if (data.get() == null) {
+            synchronized (data) {
+                if (data.get() == null) {
+                    data.set(expensiveData.get());
+                }
+            }
+        }
+        return data.get();
+    }
+
+}

core-java-modules/core-java-function/src/test/java/com/baeldung/lazylambda/LambdaSupplierUnitTest.java

@@ -0,0 +1,24 @@
+package com.baeldung.lazylambda;
+
+import java.util.function.Supplier;
+
+import org.junit.Test;
+import org.mockito.Mockito;
+
+public class LambdaSupplierUnitTest {
+
+    @Test
+    public void whenCalledMultipleTimes_thenShouldBeCalledMultipleTimes() {
+        @SuppressWarnings("unchecked") Supplier<String> mockedExpensiveFunction = Mockito.mock(Supplier.class);
+        Mockito.when(mockedExpensiveFunction.get())
+            .thenReturn("expensive call");
+        LambdaSupplier<String> testee = new LambdaSupplier<>(mockedExpensiveFunction);
+        Mockito.verify(mockedExpensiveFunction, Mockito.never())
+            .get();
+        testee.getData();
+        testee.getData();
+        Mockito.verify(mockedExpensiveFunction, Mockito.times(2))
+            .get();
+    }
+
+}

core-java-modules/core-java-function/src/test/java/com/baeldung/lazylambda/LazyLambdaSupplierUnitTest.java

@@ -0,0 +1,51 @@
+package com.baeldung.lazylambda;
+
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Supplier;
+
+import org.junit.Test;
+import org.mockito.Mockito;
+import org.mockito.stubbing.Answer;
+
+public class LazyLambdaSupplierUnitTest {
+
+    @Test
+    public void whenCalledMultipleTimes_thenShouldBeCalledOnlyOnce() {
+        @SuppressWarnings("unchecked") Supplier<String> mockedExpensiveFunction = Mockito.mock(Supplier.class);
+        Mockito.when(mockedExpensiveFunction.get())
+            .thenReturn("expensive call");
+        LazyLambdaSupplier<String> testee = new LazyLambdaSupplier<>(mockedExpensiveFunction);
+        Mockito.verify(mockedExpensiveFunction, Mockito.never())
+            .get();
+        testee.getData();
+        testee.getData();
+        Mockito.verify(mockedExpensiveFunction, Mockito.times(1))
+            .get();
+    }
+
+    @Test
+    public void whenCalledMultipleTimesConcurrently_thenShouldBeCalledMultipleTimes() throws InterruptedException {
+        @SuppressWarnings("unchecked") Supplier<String> mockedExpensiveFunction = Mockito.mock(Supplier.class);
+        Mockito.when(mockedExpensiveFunction.get())
+            .thenAnswer((Answer<String>) invocation -> {
+                Thread.sleep(1000L);
+                return "Late response!";
+            });
+        LazyLambdaSupplier<String> testee = new LazyLambdaSupplier<>(mockedExpensiveFunction);
+        Mockito.verify(mockedExpensiveFunction, Mockito.never())
+            .get();
+
+        ExecutorService executorService = Executors.newFixedThreadPool(4);
+        executorService.invokeAll(List.of(testee::getData, testee::getData));
+        executorService.shutdown();
+        if (!executorService.awaitTermination(5, TimeUnit.SECONDS)) {
+            executorService.shutdownNow();
+        }
+
+        Mockito.verify(mockedExpensiveFunction, Mockito.times(2))
+            .get();
+    }
+}

core-java-modules/core-java-function/src/test/java/com/baeldung/lazylambda/LazyLambdaThreadSafeSupplierUnitTest.java

@@ -0,0 +1,52 @@
+package com.baeldung.lazylambda;
+
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Supplier;
+
+import org.junit.Test;
+import org.mockito.Mockito;
+import org.mockito.stubbing.Answer;
+
+public class LazyLambdaThreadSafeSupplierUnitTest {
+
+    @Test
+    public void whenCalledMultipleTimes_thenShouldBeCalledOnlyOnce() {
+        @SuppressWarnings("unchecked") Supplier<String> mockedExpensiveFunction = Mockito.mock(Supplier.class);
+        Mockito.when(mockedExpensiveFunction.get())
+            .thenReturn("expensive call");
+        LazyLambdaThreadSafeSupplier<String> testee = new LazyLambdaThreadSafeSupplier<>(mockedExpensiveFunction);
+        Mockito.verify(mockedExpensiveFunction, Mockito.never())
+            .get();
+        testee.getData();
+        testee.getData();
+        Mockito.verify(mockedExpensiveFunction, Mockito.times(1))
+            .get();
+    }
+
+    @Test
+    public void whenCalledMultipleTimesConcurrently_thenShouldBeCalledOnlyOnce() throws InterruptedException {
+        @SuppressWarnings("unchecked") Supplier<String> mockedExpensiveFunction = Mockito.mock(Supplier.class);
+        Mockito.when(mockedExpensiveFunction.get())
+            .thenAnswer((Answer<String>) invocation -> {
+                Thread.sleep(1000L);
+                return "Late response!";
+            });
+        LazyLambdaThreadSafeSupplier<String> testee = new LazyLambdaThreadSafeSupplier<>(mockedExpensiveFunction);
+        Mockito.verify(mockedExpensiveFunction, Mockito.never())
+            .get();
+
+        ExecutorService executorService = Executors.newFixedThreadPool(4);
+        executorService.invokeAll(List.of(testee::getData, testee::getData));
+        executorService.shutdown();
+        if (!executorService.awaitTermination(5, TimeUnit.SECONDS)) {
+            executorService.shutdownNow();
+        }
+
+        Mockito.verify(mockedExpensiveFunction, Mockito.times(1))
+            .get();
+    }
+
+}

core-java-modules/core-java-io-5/src/main/java/com/baeldung/splitlargefile/SplitLargeFile.java

@@ -0,0 +1,59 @@
+package com.baeldung.splitlargefile;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.commons.io.FilenameUtils;
+
+class SplitLargeFile {
+
+    public List<File> splitByFileSize(File largeFile, int maxSizeOfSplitFiles,
+            String splitedFileDirPath) throws IOException {
+        List<File> listOfSplitFiles = new ArrayList<>();
+        try (InputStream in = Files.newInputStream(largeFile.toPath())) {
+            final byte[] buffer = new byte[maxSizeOfSplitFiles];
+            int dataRead = in.read(buffer);
+            while (dataRead > -1) {
+                File splitFile = getSplitFile(FilenameUtils.removeExtension(largeFile.getName()),
+                        buffer, dataRead, splitedFileDirPath);
+                listOfSplitFiles.add(splitFile);
+                dataRead = in.read(buffer);
+            }
+        }
+        return listOfSplitFiles;
+    }
+
+    private File getSplitFile(String largeFileName, byte[] buffer, int length,
+            String splitedFileDirPath) throws IOException {
+        File splitFile = File.createTempFile(largeFileName + "-", "-split",
+                new File(splitedFileDirPath));
+        try (FileOutputStream fos = new FileOutputStream(splitFile)) {
+            fos.write(buffer, 0, length);
+        }
+        return splitFile;
+    }
+
+    public List<File> splitByNumberOfFiles(File largeFile, int noOfFiles, String splitedFileDirPath)
+            throws IOException {
+        return splitByFileSize(largeFile, getSizeInBytes(largeFile.length(), noOfFiles),
+                splitedFileDirPath);
+    }
+
+    private int getSizeInBytes(long largefileSizeInBytes, int numberOfFilesforSplit) {
+        if (largefileSizeInBytes % numberOfFilesforSplit != 0) {
+            largefileSizeInBytes = ((largefileSizeInBytes / numberOfFilesforSplit) + 1)
+                    * numberOfFilesforSplit;
+        }
+        long x = largefileSizeInBytes / numberOfFilesforSplit;
+        if (x > Integer.MAX_VALUE) {
+            throw new NumberFormatException("size too large");
+
+        }
+        return (int) x;
+    }
+}

core-java-modules/core-java-io-5/src/test/java/com/baeldung/outputstreamtobytearray/OutputStreamToByteArrayUnitTest.java

@@ -0,0 +1,62 @@
+package com.baeldung.outputstreamtobytearray;
+
+import org.apache.commons.io.FileUtils;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.*;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class OutputStreamToByteArrayUnitTest {
+
+    @Test
+    public void givenFileOutputStream_whenUsingFileUtilsToReadTheFile_thenReturnByteArray(@TempDir Path tempDir) throws IOException {
+        String data = "Welcome to Baeldung!";
+        String fileName = "file.txt";
+        Path filePath = tempDir.resolve(fileName);
+
+        try (FileOutputStream outputStream = new FileOutputStream(filePath.toFile())) {
+            outputStream.write(data.getBytes(StandardCharsets.UTF_8));
+        }
+
+        byte[] writtenData = FileUtils.readFileToByteArray(filePath.toFile());
+        String result = new String(writtenData, StandardCharsets.UTF_8);
+        assertEquals(data, result);
+    }
+
+
+    @Test
+    public void givenSystemOut_whenUsingDrainableOutputStream_thenReturnByteArray() throws IOException {
+        String data = "Welcome to Baeldung!\n";
+
+        DrainableOutputStream drainableOutputStream = new DrainableOutputStream(System.out);
+        try (drainableOutputStream) {
+            drainableOutputStream.write(data.getBytes(StandardCharsets.UTF_8));
+        }
+
+        byte[] writtenData = drainableOutputStream.toByteArray();
+        assertEquals(data, new String(writtenData, StandardCharsets.UTF_8));
+    }
+
+    public class DrainableOutputStream extends FilterOutputStream {
+        private final ByteArrayOutputStream buffer;
+
+        public DrainableOutputStream(OutputStream out) {
+            super(out);
+            this.buffer = new ByteArrayOutputStream();
+        }
+
+        @Override
+        public void write(byte b[]) throws IOException {
+            buffer.write(b);
+            super.write(b);
+        }
+
+        public byte[] toByteArray() {
+            return buffer.toByteArray();
+        }
+    }
+}

core-java-modules/core-java-io-5/src/test/java/com/baeldung/splitlargefile/SplitLargeFileUnitTest.java

@@ -0,0 +1,41 @@
+package com.baeldung.splitlargefile;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+import org.junit.BeforeClass;
+
+public class SplitLargeFileUnitTest {
+
+    @BeforeClass
+    public static void prepareData() throws IOException {
+        Files.createDirectories(Paths.get("target/split"));
+    }
+
+    private String splitedFileDirPath() throws Exception {
+        return Paths.get("target").toString() + "/split";
+    }
+
+    private Path largeFilePath() throws Exception {
+        return Paths.get(this.getClass().getClassLoader().getResource("large-file.txt").toURI());
+    }
+
+
+    @org.junit.Test
+    public void givenLargeFile_whenSplitLargeFile_thenSplitBySize() throws Exception {
+        File input = largeFilePath().toFile();
+        SplitLargeFile slf = new SplitLargeFile();
+        slf.splitByFileSize(input, 1024_000, splitedFileDirPath());
+    }
+
+    @org.junit.Test
+    public void givenLargeFile_whenSplitLargeFile_thenSplitByNumberOfFiles() throws Exception {
+        File input = largeFilePath().toFile();
+        SplitLargeFile slf = new SplitLargeFile();
+        slf.splitByNumberOfFiles(input, 3, splitedFileDirPath());
+    }
+
+}

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

@@ -0,0 +1,2 @@
+## Relevant Articles
+- [Inter-Process Communication Methods in Java](https://www.baeldung.com/java-ipc)

core-java-modules/core-java-lang-6/README.md

@@ -10,3 +10,4 @@ This module contains articles about core features in the Java language
 - [Stop Executing Further Code in Java](https://www.baeldung.com/java-stop-running-code)
 - [Using the Apache Commons Lang 3 for Comparing Objects in Java](https://www.baeldung.com/java-apache-commons-lang-3-compare-objects)
 - [Return First Non-null Value in Java](https://www.baeldung.com/java-first-non-null)
+- [Static Final Variables in Java](https://www.baeldung.com/java-static-final-variables)

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

@@ -23,6 +23,16 @@
             <artifactId>commons-lang3</artifactId>
             <version>${commons-lang3.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
     </dependencies>
     <build>
         <plugins>
@@ -39,6 +49,11 @@
                             <artifactId>mapstruct-processor</artifactId>
                             <version>${mapstruct.version}</version>
                         </path>
+                        <path>
+                            <groupId>org.openjdk.jmh</groupId>
+                            <artifactId>jmh-generator-annprocess</artifactId>
+                            <version>${jmh.version}</version>
+                        </path>
                     </annotationProcessorPaths>
                 </configuration>
             </plugin>
@@ -50,6 +65,7 @@
         <maven.compiler.target>17</maven.compiler.target>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <mapstruct.version>1.6.0.Beta1</mapstruct.version>
+        <jmh.version>1.37</jmh.version>
     </properties>
 
 </project>

core-java-modules/core-java-lang-6/src/main/java/com/baeldung/compressbytes/CompressByteArrayUtil.java

@@ -23,6 +23,23 @@ public class CompressByteArrayUtil {
         return outputStream.toByteArray();
     }
 
+    public static byte[] compressWithCustomLevel(byte[] input, int level) {
+        Deflater deflater = new Deflater();
+        deflater.setInput(input);
+        deflater.setLevel(level);
+        deflater.finish();
+
+        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+        byte[] buffer = new byte[1024];
+
+        while (!deflater.finished()) {
+            int compressedSize = deflater.deflate(buffer);
+            outputStream.write(buffer, 0, compressedSize);
+        }
+
+        return outputStream.toByteArray();
+    }
+
     public static byte[] decompress(byte[] input) throws DataFormatException {
         Inflater inflater = new Inflater();
         inflater.setInput(input);

core-java-modules/core-java-lang-6/src/main/java/com/baeldung/staticfinal/Bike.java

@@ -0,0 +1,14 @@
+package com.baeldung.staticfinal;
+
+import java.util.HashMap;
+
+public class Bike {
+    public static final int TIRE = 2;
+    public static final int PEDAL;
+    public static final HashMap<String, Integer> PART = new HashMap<>();
+
+    static {
+        PEDAL = 5;
+    }
+
+}

core-java-modules/core-java-lang-6/src/test/java/com/baeldung/compressbytes/CompressByteArrayUnitTest.java

@@ -0,0 +1,39 @@
+package com.baeldung.compressbytes;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.zip.DataFormatException;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class CompressByteArrayUnitTest {
+
+    private static final String INPUT_STRING = "Building a REST API is not a trivial task – from the high-level RESTful " +
+            "constraints down to the nitty-gritty of making everything work and work well." +
+            "Spring has made REST a first-class citizen and the platform has been maturing in leaps and bounds." +
+            "With this guide, my aim is to organize the mountains of information that are available on the subject and " +
+            "guide you through properly building an API." +
+            "The guide starts with the basics – bootstrapping the REST API, the Spring MVC Configuration, and basic customization.";
+
+    @Test
+    void givenInputString_whenCompressWithDefaultLevel_thenDecompressWithSameSize() throws DataFormatException {
+        byte[] input = INPUT_STRING.getBytes();
+        byte[] compressedData = CompressByteArrayUtil.compress(input);
+        byte[] decompressedData = CompressByteArrayUtil.decompress(compressedData);
+        System.out.println("Original: " + input.length + " bytes");
+        System.out.println("Compressed: " + compressedData.length + " bytes");
+        System.out.println("Decompressed: " + decompressedData.length + " bytes");
+        assertEquals(input.length, decompressedData.length);
+    }
+
+    @Test
+    void givenInputString_whenCompressWithCustomLevel_thenDecompressWithSameSize() throws DataFormatException {
+        byte[] input = INPUT_STRING.getBytes();
+        byte[] compressedData = CompressByteArrayUtil.compressWithCustomLevel(input, 1);
+        byte[] decompressedData = CompressByteArrayUtil.decompress(compressedData);
+        System.out.println("Original: " + input.length + " bytes");
+        System.out.println("Compressed: " + compressedData.length + " bytes");
+        System.out.println("Decompressed: " + decompressedData.length + " bytes");
+        assertEquals(input.length, decompressedData.length);
+    }
+}

core-java-modules/core-java-lang-6/src/test/java/com/baeldung/recursivelysumintarray/RecursivelySumIntArrayUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.recursivelysumintarray;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class RecursivelySumIntArrayUnitTest {
+
+    private static final int[] INT_ARRAY = { 1, 2, 3, 4, 5 };
+
+    static int sumIntArray1(int[] array) {
+        if (array.length == 1) {
+            return array[0];
+        } else {
+            return array[0] + sumIntArray1(Arrays.copyOfRange(array, 1, array.length));
+        }
+    }
+
+    static int sumIntArray2(int[] array, int index) {
+        if (index == 0) {
+            return array[index];
+        } else {
+            return array[index] + sumIntArray2(array, index - 1);
+        }
+    }
+
+    @Test
+    void whenUsingSumIntArray1_thenGetExpectedResult() {
+        assertEquals(15, sumIntArray1(INT_ARRAY));
+    }
+
+    @Test
+    void whenUsingSumIntArray2_thenGetExpectedResult() {
+        assertEquals(15, sumIntArray2(INT_ARRAY, INT_ARRAY.length - 1));
+    }
+}

core-java-modules/core-java-lang-6/src/test/java/com/baeldung/recursivelysumintarray/SumArrayBenchmark.java

@@ -0,0 +1,61 @@
+package com.baeldung.recursivelysumintarray;
+
+import static com.baeldung.recursivelysumintarray.RecursivelySumIntArrayUnitTest.sumIntArray1;
+import static com.baeldung.recursivelysumintarray.RecursivelySumIntArrayUnitTest.sumIntArray2;
+
+import java.util.Random;
+import java.util.concurrent.TimeUnit;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+@BenchmarkMode(Mode.AverageTime)
+@State(Scope.Thread)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@Warmup(iterations = 2)
+@Fork(1)
+@Measurement(iterations = 5)
+public class SumArrayBenchmark {
+
+    public static void main(String[] args) throws Exception {
+        Options options = new OptionsBuilder().include(SumArrayBenchmark.class.getSimpleName())
+          .build();
+        new Runner(options).run();
+    }
+
+    @Param({ "10", "10000" })
+    public int size;
+    int[] array;
+
+    @Setup
+    public void setup() {
+        var r = new Random();
+        array = new int[size];
+
+        for (int i = 0; i < size; i++) {
+            array[i] = r.nextInt();
+        }
+    }
+
+    @Benchmark
+    public int withArrayCopy() {
+        return sumIntArray1(array);
+    }
+
+    @Benchmark
+    public int withoutArrayCopy() {
+        return sumIntArray2(array, array.length - 1);
+    }
+}

core-java-modules/core-java-lang-6/src/test/java/com/baeldung/staticfinal/BikeUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.staticfinal;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class BikeUnitTest {
+
+    @Test
+    void givenTireConstantSetUponDeclaration_whenGetTire_thenReturnTwo() {
+        assertEquals(2, Bike.TIRE);
+    }
+
+    @Test
+    void givenPedalConstantSetByStaticBlock_whenGetPedal_thenReturnFive() {
+        assertEquals(5, Bike.PEDAL);
+    }
+
+    @Test
+    void givenPartConstantObject_whenObjectStateChanged_thenCorrect() {
+        Bike.PART.put("seat", 1);
+        assertEquals(1, Bike.PART.get("seat"));
+
+        Bike.PART.put("seat", 5);
+        assertEquals(5, Bike.PART.get("seat"));
+    }
+
+    @Test
+    void givenMathClass_whenAccessingPiConstant_thenVerifyPiValueIsCorrect() {
+        assertEquals(3.141592653589793, Math.PI);
+    }
+
+}

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

@@ -5,6 +5,14 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>core-java-lang-math</artifactId>
     <name>core-java-lang-math</name>
+    <dependencies>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+            <scope>compile</scope>
+        </dependency>
+    </dependencies>
     <packaging>jar</packaging>
 
     <parent>

core-java-modules/core-java-lang-math/src/main/java/com/baeldung/algorithms/percentage/BigDecimalPercentageCalculator.java

@@ -0,0 +1,20 @@
+package com.baeldung.algorithms.percentage;
+
+import lombok.experimental.ExtensionMethod;
+import java.math.BigDecimal;
+import java.util.Scanner;
+
+@ExtensionMethod(FastBigDecimalPercentage.class)
+public class BigDecimalPercentageCalculator {
+    public static void main(String[] args) {
+
+        Scanner in = new Scanner(System.in);
+        System.out.println("Enter obtained marks:");
+        BigDecimal obtained = new BigDecimal(in.nextDouble());
+        System.out.println("Enter total marks:");
+        BigDecimal total = new BigDecimal(in.nextDouble());
+
+        System.out.println("Percentage obtained :"+ obtained.toPercentageOf(total));
+    }
+
+}

core-java-modules/core-java-lang-math/src/main/java/com/baeldung/algorithms/percentage/BigDecimalPercentages.java

@@ -0,0 +1,18 @@
+package com.baeldung.algorithms.percentage;
+
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
+public class BigDecimalPercentages {
+
+    private static final BigDecimal ONE_HUNDRED = new BigDecimal("100");
+
+    public BigDecimal toPercentageOf(BigDecimal value, BigDecimal total) {
+        return value.divide(total, 4, RoundingMode.HALF_UP).multiply(ONE_HUNDRED);
+    }
+
+    public BigDecimal percentOf(BigDecimal percentage, BigDecimal total) {
+        return percentage.multiply(total).divide(ONE_HUNDRED, 2, RoundingMode.HALF_UP);
+    }
+}

core-java-modules/core-java-lang-math/src/main/java/com/baeldung/algorithms/percentage/FastBigDecimalPercentage.java

@@ -0,0 +1,16 @@
+package com.baeldung.algorithms.percentage;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
+public class FastBigDecimalPercentage {
+
+    public static BigDecimal toPercentageOf(BigDecimal value, BigDecimal total) {
+        return value.divide(total, 4, RoundingMode.HALF_UP).scaleByPowerOfTen(2);
+    }
+
+    public static BigDecimal percentOf(BigDecimal percentage, BigDecimal total) {
+        return percentage.multiply(total).scaleByPowerOfTen(-2);
+    }
+
+}

core-java-modules/core-java-lang-math/src/test/java/com/baeldung/algorithms/percentage/BigDecimalPercentageUnitTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.algorithms.percentage;
+
+import org.hamcrest.number.BigDecimalCloseTo;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.math.BigDecimal;
+
+public class BigDecimalPercentageUnitTest {
+    private BigDecimalPercentages pc = new BigDecimalPercentages();
+
+
+    @Test
+    public void shouldConvertToPercentageOfTotal(){
+        BigDecimalCloseTo expected = new BigDecimalCloseTo(new BigDecimal(5.05), new BigDecimal(0.001));
+        Assert.assertTrue("Result not as expected",expected.matchesSafely(
+                pc.toPercentageOf(new BigDecimal(50.5),new BigDecimal(1000))));
+    }
+
+    @Test
+    public void shouldCalculatePercentageOfTotal(){
+        BigDecimalCloseTo expected = new BigDecimalCloseTo(new BigDecimal(31.40), new BigDecimal(0.001));
+        Assert.assertTrue("Result not as expected",expected.matchesSafely(
+                pc.percentOf(new BigDecimal(3.14),new BigDecimal(1000))));
+    }
+
+}

core-java-modules/core-java-lang-math/src/test/java/com/baeldung/algorithms/percentage/FastBigDecimalPercentageUnitTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.algorithms.percentage;
+
+import org.hamcrest.number.BigDecimalCloseTo;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.math.BigDecimal;
+
+public class FastBigDecimalPercentageUnitTest {
+    private FastBigDecimalPercentage pc = new FastBigDecimalPercentage();
+
+
+    @Test
+    public void shouldConvertToPercentageOfTotal(){
+        BigDecimalCloseTo expected = new BigDecimalCloseTo(new BigDecimal(5.05), new BigDecimal(0.001));
+        Assert.assertTrue("Result not as expected",expected.matchesSafely(
+                pc.toPercentageOf(new BigDecimal(50.5),new BigDecimal(1000))));
+    }
+
+    @Test
+    public void shouldCalculatePercentageOfTotal(){
+        BigDecimalCloseTo expected = new BigDecimalCloseTo(new BigDecimal(31.40), new BigDecimal(0.001));
+        Assert.assertTrue("Result not as expected",expected.matchesSafely(
+                pc.percentOf(new BigDecimal(3.14),new BigDecimal(1000))));
+    }
+
+}

core-java-modules/core-java-lang-oop-generics/pom.xml

@@ -37,8 +37,8 @@
     </build>
 
     <properties>
-        <maven.compiler.source>1.8</maven.compiler.source>
-        <maven.compiler.target>1.8</maven.compiler.target>
+        <maven.compiler.source>17</maven.compiler.source>
+        <maven.compiler.target>17</maven.compiler.target>
     </properties>
 
 </project>

core-java-modules/core-java-lang-oop-generics/src/main/java/com/baeldung/generics/classtype/CollectionWithAndWithoutGenerics.java

@@ -0,0 +1,33 @@
+package com.baeldung.generics.classtype;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class CollectionWithAndWithoutGenerics {
+
+    public static void main(String[] args) {
+        withoutGenerics();
+    }
+
+    private static void withoutGenerics() {
+        List container = new ArrayList();
+        container.add(1);
+        container.add("2");
+        container.add("string");
+
+        for (int i = 0; i < container.size(); i++) {
+            int val = (int) container.get(i);
+        }
+    }
+
+    public static void withGenerics() {
+        List<Integer> container = new ArrayList();
+        container.add(1);
+        container.add(2);
+        container.add(3);
+
+        for (int i = 0; i < container.size(); i++) {
+            int val = container.get(i);
+        }
+    }
+}

core-java-modules/core-java-lang-oop-generics/src/main/java/com/baeldung/generics/classtype/ContainerTypeFromReflection.java

@@ -0,0 +1,13 @@
+package com.baeldung.generics.classtype;
+
+public class ContainerTypeFromReflection<T> {
+    private T content;
+
+    public ContainerTypeFromReflection(T content) {
+        this.content = content;
+    }
+
+    public Class<?> getClazz() {
+        return this.content.getClass();
+    }
+}

core-java-modules/core-java-lang-oop-generics/src/main/java/com/baeldung/generics/classtype/ContainerTypeFromTypeParameter.java

@@ -0,0 +1,13 @@
+package com.baeldung.generics.classtype;
+
+public class ContainerTypeFromTypeParameter<T> {
+    private Class<T> clazz;
+
+    public ContainerTypeFromTypeParameter(Class<T> clazz) {
+        this.clazz = clazz;
+    }
+
+    public Class<T> getClazz() {
+        return this.clazz;
+    }
+}

core-java-modules/core-java-lang-oop-generics/src/main/java/com/baeldung/generics/classtype/TypeToken.java

@@ -0,0 +1,17 @@
+package com.baeldung.generics.classtype;
+
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+
+public abstract class TypeToken<T> {
+    private Type type;
+
+    protected TypeToken(){
+        Type superclass = getClass().getGenericSuperclass();
+        this.type = ((ParameterizedType) superclass).getActualTypeArguments()[0];
+    }
+
+    public Type getType() {
+        return type;
+    }
+}

core-java-modules/core-java-lang-oop-generics/src/test/java/com/baeldung/classtype/GenericClassTypeUnitTest.java

@@ -0,0 +1,47 @@
+package com.baeldung.classtype;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import com.baeldung.generics.classtype.ContainerTypeFromReflection;
+import com.baeldung.generics.classtype.ContainerTypeFromTypeParameter;
+import com.baeldung.generics.classtype.TypeToken;
+
+public class GenericClassTypeUnitTest {
+
+    @Test
+    public void givenContainerClassWithGenericType_whenTypeParameterUsed_thenReturnsClassType() {
+        var stringContainer = new ContainerTypeFromTypeParameter<>(String.class);
+        Class<String> containerClass = stringContainer.getClazz();
+
+        assertEquals(containerClass, String.class);
+    }
+
+    @Test
+    public void givenContainerClassWithGenericType_whenReflectionUsed_thenReturnsClassType() {
+        var stringContainer = new ContainerTypeFromReflection<>("Hello Java");
+        Class<?> stringClazz = stringContainer.getClazz();
+        assertEquals(stringClazz, String.class);
+
+        var integerContainer = new ContainerTypeFromReflection<>(1);
+        Class<?> integerClazz = integerContainer.getClazz();
+        assertEquals(integerClazz, Integer.class);
+    }
+
+    @Test
+    public void giveContainerClassWithGenericType_whenTypeTokenUsed_thenReturnsClassType() {
+        class ContainerTypeFromTypeToken extends TypeToken<List<String>> {
+        }
+
+        var container = new ContainerTypeFromTypeToken();
+        ParameterizedType type = (ParameterizedType) container.getType();
+        Type actualTypeArgument = type.getActualTypeArguments()[0];
+
+        assertEquals(actualTypeArgument, String.class);
+    }
+}

core-java-modules/core-java-lang-operators-2/README.md

@@ -10,3 +10,4 @@ This module contains articles about Java operators
 - [Check if at Least Two Out of Three Booleans Are True in Java](https://www.baeldung.com/java-check-two-of-three-booleans)
 - [Alternatives for instanceof Operator in Java](https://www.baeldung.com/java-instanceof-alternatives)
 - [What Does “––>” Mean in Java?](https://www.baeldung.com/java-minus-minus-greaterthan)
+- [All the Ways Java Uses the Colon Character](https://www.baeldung.com/java-colon)

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

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

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

@@ -0,0 +1,16 @@
+<?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-loops</artifactId>
+    <name>core-java-loops</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-loops/src/test/java/com/baeldung/loops/TheLastIterationInForEachUnitTest.java

@@ -0,0 +1,93 @@
+package com.baeldung.loops;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.IntStream;
+
+import org.junit.jupiter.api.Test;
+
+public class TheLastIterationInForEachUnitTest {
+
+    //@formatter:off
+    private static final List<String> MOVIES = List.of(
+      "Titanic",
+      "The Deer Hunter",
+      "Lord of the Rings",
+      "One Flew Over the Cuckoo's Nest",
+      "No Country For Old Men");
+    //@formatter:on
+
+    @Test
+    void whenUsingForEach_thenGetTheLastElementAfterTheLoop() {
+        String myLastMovie = "";
+        for (String movie : MOVIES) {
+            // ... work with movie
+            myLastMovie = movie;
+        }
+        assertEquals("No Country For Old Men", myLastMovie);
+    }
+
+    @Test
+    void whenLoopingWithIndexes_thenGetExpectedResult() {
+        int size = MOVIES.size();
+        String myLastMovie = null;
+        for (int i = 0; i < size; i++) {
+            String movie = MOVIES.get(i);
+            // ... work with movie
+            if (i == size - 1) {
+                myLastMovie = movie;
+            }
+        }
+        assertEquals("No Country For Old Men", myLastMovie);
+    }
+
+    @Test
+    void whenUsingIntStream_thenGetExpectedResult() {
+        int size = MOVIES.size();
+        final Map<Integer, String> myLastMovie = new HashMap<>();
+        IntStream.range(0, size)
+            .forEach(idx -> {
+                String movie = MOVIES.get(idx);
+                // ... work with movie
+                if (idx == size - 1) {
+                    myLastMovie.put(idx, movie);
+                }
+            });
+        assertEquals(1, myLastMovie.size());
+        assertTrue(myLastMovie.containsKey(size - 1));
+        assertTrue(myLastMovie.containsValue("No Country For Old Men"));
+    }
+
+    @Test
+    void whenUsingCounter_thenGetExpectedResult() {
+        int size = MOVIES.size();
+        String myLastMovie = null;
+        int cnt = 0;
+        for (String movie : MOVIES) {
+            // ... work with movie
+            if (++cnt == size) {
+                myLastMovie = movie;
+            }
+        }
+        assertEquals("No Country For Old Men", myLastMovie);
+    }
+
+    @Test
+    void whenUsingIterator_thenGetExpectedResult() {
+        String movie;
+        String myLastMovie = null;
+        for (Iterator<String> it = MOVIES.iterator(); it.hasNext(); ) {
+            movie = it.next();
+            // ... work with movie
+            if (!it.hasNext()) { // the last element
+                myLastMovie = movie;
+            }
+        }
+        assertEquals("No Country For Old Men", myLastMovie);
+    }
+}

core-java-modules/core-java-numbers-7/README.md

@@ -0,0 +1,2 @@
+## Relevant Articles
+- [Check if a double Is an Integer in Java](https://www.baeldung.com/java-check-double-integer)

core-java-modules/core-java-numbers-7/src/test/java/com/baeldung/withoutscientificnotation/PrintDoubleWithoutScientificNotationUnitTest.java

@@ -0,0 +1,113 @@
+package com.baeldung.withoutscientificnotation;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.math.BigDecimal;
+import java.text.DecimalFormat;
+import java.util.Locale;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class PrintDoubleWithoutScientificNotationUnitTest {
+
+    private final PrintStream standardOut = System.out;
+    private final ByteArrayOutputStream outputStreamCaptor = new ByteArrayOutputStream();
+
+    @BeforeEach
+    public void setUp() {
+        System.setOut(new PrintStream(outputStreamCaptor));
+        Locale.setDefault(Locale.US);
+    }
+
+    @AfterEach
+    public void tearDown() {
+        System.setOut(standardOut);
+    }
+
+    @Test
+    void givenLargeNumber_whenPrintWithDecimalFormat_thenOutputIsWithoutScientificNotation() {
+
+        DecimalFormat df = new DecimalFormat("#.###########");
+        double largeNumber = 256450000d;
+        System.out.println("Large Number: " + df.format(largeNumber));
+
+        Assertions.assertEquals("Large Number: 256450000", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenSmallNumber_whenPrintWithDecimalFormat_thenOutputIsWithoutScientificNotation() {
+
+        DecimalFormat df = new DecimalFormat("#.###########");
+        double smallNumber = 0.0000046d;
+        System.out.println("Small Number: " + df.format(smallNumber));
+
+        Assertions.assertEquals("Small Number: 0.0000046", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenLargeNumber_whenPrintWithPrintf_thenOutputIsWithoutScientificNotation() {
+
+        double largeNumber = 256450000d;
+        System.out.printf("Large Number: %.7f", largeNumber);
+
+        Assertions.assertEquals("Large Number: 256450000.0000000", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenSmallNumber_whenPrintWithPrintf_thenOutputIsWithoutScientificNotation() {
+
+        double smallNumber = 0.0000046d;
+        System.out.printf("Small Number: %.7f", smallNumber);
+
+        Assertions.assertEquals("Small Number: 0.0000046", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenLargeNumber_whenPrintWithBigDecimal_thenOutputIsWithoutScientificNotation() {
+
+        double largeNumber = 256450000d;
+        System.out.println("Large Number: " + BigDecimal.valueOf(largeNumber).toPlainString());
+
+        Assertions.assertEquals("Large Number: 256450000", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenSmallNumber_whenPrintWithBigDecimal_thenOutputIsWithoutScientificNotation() {
+
+        double smallNumber = 0.0000046d;
+        System.out.println("Small Number: " + BigDecimal.valueOf(smallNumber).toPlainString());
+
+        Assertions.assertEquals("Small Number: 0.0000046", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenLargeNumber_whenPrintWithStringFormat_thenOutputIsWithoutScientificNotation() {
+
+        double largeNumber = 256450000d;
+        String formattedLargeNumber = String.format("%.7f", largeNumber);
+        System.out.println("Large Number: " + formattedLargeNumber);
+
+        Assertions.assertEquals("Large Number: 256450000.0000000", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenSmallNumber_whenPrintWithStringFormat_thenOutputIsWithoutScientificNotation() {
+
+        double smallNumber = 0.0000046d;
+        String formattedSmallNumber = String.format("%.7f", smallNumber);
+        System.out.println("Small Number: " + formattedSmallNumber);
+
+        Assertions.assertEquals("Small Number: 0.0000046", outputStreamCaptor.toString()
+          .trim());
+    }
+}

core-java-modules/core-java-numbers-conversions/README.md

@@ -4,3 +4,5 @@
 - [Convert int to Long in Java](https://www.baeldung.com/java-convert-int-long)
 - [How To Convert Double To Float In Java](https://www.baeldung.com/java-convert-double-float)
 - [Converting from float to BigDecimal in Java](https://www.baeldung.com/java-convert-float-bigdecimal)
+- [Convert Positive Integer to Negative and Vice Versa in Java](https://www.baeldung.com/java-negating-integer)
+- [Rounding Up a Number to Nearest Multiple of 5 in Java](https://www.baeldung.com/java-round-nearest-multiple-five)

core-java-modules/core-java-perf/src/test/java/com/baeldung/branchprediction/CombiningUnitTest.java

@@ -9,7 +9,7 @@ import org.slf4j.LoggerFactory;
 public class CombiningUnitTest {
     private static final Logger LOG = LoggerFactory.getLogger(CombiningUnitTest.class);
 
-    public static final int TOP = 10000000;
+    public static final int TOP = 1000000;
     public static final double FRACTION = 0.1;
 
     @Test

core-java-modules/core-java-perf/src/test/java/com/baeldung/branchprediction/IfUnitTest.java

@@ -12,7 +12,7 @@ import org.slf4j.LoggerFactory;
 public class IfUnitTest {
     private static final Logger LOG = LoggerFactory.getLogger(IfUnitTest.class);
 
-    public static final int TOP = 10000000;
+    public static final int TOP = 1000000;
 
     @Test
     public void majorBranchSorted() {

core-java-modules/core-java-perf/src/test/java/com/baeldung/branchprediction/SortingUnitTest.java

@@ -11,7 +11,7 @@ import org.slf4j.LoggerFactory;
 
 public class SortingUnitTest {
     private static final Logger LOG = LoggerFactory.getLogger(SortingUnitTest.class);
-    public static final int BIG = 10000000;
+    public static final int BIG = 1000000;
     public static final int SMALL = 100000;
 
     @Test

core-java-modules/core-java-streams-3/README.md

@@ -11,4 +11,4 @@ This module contains articles about the Stream API in Java.
 - [Should We Close a Java Stream?](https://www.baeldung.com/java-stream-close)
 - [Returning Stream vs. Collection](https://www.baeldung.com/java-return-stream-collection)
 - [Convert a Java Enumeration Into a Stream](https://www.baeldung.com/java-enumeration-to-stream)
-- More articles: [[<-- prev>]](/../core-java-streams-2)
+- More articles: [[<-- prev>]](/../core-java-streams-2) [[next -->]](/../core-java-streams-4)

core-java-modules/core-java-streams-4/README.md

@@ -10,3 +10,4 @@
 - [Understanding the Difference Between Stream.of() and IntStream.range()](https://www.baeldung.com/java-stream-of-and-intstream-range)
 - [Check if Object Is an Array in Java](https://www.baeldung.com/java-check-if-object-is-an-array)
 - [Mapping an Array of Integers to Strings Using Java Streams](https://www.baeldung.com/java-stream-integer-array-to-strings)
+- More articles: [[<-- prev>]](/../core-java-streams-3) [[next -->]](/../core-java-streams-5)

core-java-modules/core-java-streams-4/pom.xml

@@ -71,7 +71,7 @@
         <dependency>
             <groupId>io.projectreactor</groupId>
             <artifactId>reactor-core</artifactId>
-            <version>${io.reactor3.version}</version>
+            <version>${reactor-core.version}</version>
         </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
@@ -121,7 +121,7 @@
         <rx.java2.version>2.2.2</rx.java2.version>
         <rx.java3.version>3.1.5</rx.java3.version>
         <io.varv.version>1.0.0-alpha-4</io.varv.version>
-        <io.reactor3.version>3.5.1</io.reactor3.version>
+        <reactor-core.version>3.6.0</reactor-core.version>
         <apache.commons.collection4.version>4.4</apache.commons.collection4.version>
         <cyclops.version>10.4.1</cyclops.version>
     </properties>

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

@@ -6,5 +6,7 @@
 - [Partition a Stream in Java](https://www.baeldung.com/java-partition-stream)
 - [Taking Every N-th Element from Finite and Infinite Streams in Java](https://www.baeldung.com/java-nth-element-finite-infinite-streams)
 - [Modifying Objects Within Stream While Iterating](https://www.baeldung.com/java-stream-modify-objects-during-iteration)
-- [Convert a Stream into a Map or Multimap in Java](https://www.baeldung.com/java-convert-stream-map-multimap)
 - [How to Avoid NoSuchElementException in Stream API](https://www.baeldung.com/java-streams-api-avoid-nosuchelementexception)
+- [Get Index of First Element Matching Boolean Using Java Streams](https://www.baeldung.com/java-streams-find-first-match-index)
+- [Handling NullPointerException in findFirst() When the First Element Is Null](https://www.baeldung.com/java-handle-nullpointerexception-findfirst-first-null)
+- More articles: [[<-- prev>]](/../core-java-streams-4)

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

@@ -67,7 +67,6 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>${maven-compiler-plugin.version}</version>
                 <configuration>
                     <source>${maven.compiler.source}</source>
                     <target>${maven.compiler.target}</target>

core-java-modules/core-java-streams-5/src/test/java/com/baeldung/findfirstnullpointerexception/FindFirstNullPointerExceptionUnitTest.java

@@ -0,0 +1,42 @@
+package com.baeldung.findfirstnullpointerexception;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.function.Function;
+
+import org.junit.Test;
+
+public class FindFirstNullPointerExceptionUnitTest {
+
+    private final List<String> inputs = Arrays.asList(null, "foo", "bar");
+
+    @Test(expected = NullPointerException.class)
+    public void givenStream_whenCallingFindFirst_thenThrowNullPointerException() {
+        Optional<String> firstElement = inputs.stream()
+          .findFirst();
+    }
+
+    @Test
+    public void givenStream_whenUsingOfNullableBeforeFindFirst_thenCorrect() {
+        Optional<String> firstElement = inputs.stream()
+          .map(Optional::ofNullable)
+          .findFirst()
+          .flatMap(Function.identity());
+
+        assertTrue(firstElement.isEmpty());
+    }
+
+    @Test
+    public void givenStream_whenUsingFilterBeforeFindFirst_thenCorrect() {
+        Optional<String> firstNonNullElement = inputs.stream()
+          .filter(Objects::nonNull)
+          .findFirst();
+
+        assertTrue(firstNonNullElement.isPresent());
+    }
+
+}

core-java-modules/core-java-streams-5/src/test/java/com/baeldung/streams/firstmatchingelement/FirstMatchingElementUnitTest.java

@@ -34,7 +34,7 @@ public class FirstMatchingElementUnitTest {
 
     @Test
     public void whenUsingIntStream_thenFindFirstMatchingUserIndex() {
-        int index = IntStream.range(0, userList.size() - 1)
+        int index = IntStream.range(0, userList.size())
           .filter(streamIndex -> searchName.equals(userList.get(streamIndex).getUserName()))
           .findFirst()
           .orElse(-1);

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

@@ -1,2 +1,3 @@
 ## Relevant Articles:
 - [Handle Duplicate Keys When Producing Map Using Java Stream](https://www.baeldung.com/java-duplicate-keys-when-producing-map-using-stream)
+- [Convert a Stream into a Map or Multimap in Java](https://www.baeldung.com/java-convert-stream-map-multimap)

core-java-modules/core-java-streams-maps/pom.xml

@@ -46,7 +46,6 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>${maven-compiler-plugin.version}</version>
                 <configuration>
                     <source>${maven.compiler.source}</source>
                     <target>${maven.compiler.target}</target>