Merge pull request #2 from eugenp/master

merge

.gitignore

@@ -1,4 +1,5 @@
 */bin/*
+bin/
 
 *.class
 
@@ -21,6 +22,9 @@
 *.iws
 out/
 
+# VSCode
+.vscode/
+
 # Mac
 .DS_Store
 
@@ -77,4 +81,5 @@ apache-avro/src/main/java/com/baeldung/avro/model/
 jta/transaction-logs/
 software-security/sql-injection-samples/derby.log
 spring-soap/src/main/java/com/baeldung/springsoap/gen/
-/report-*.json
+/report-*.json
+transaction.log

algorithms-miscellaneous-1/pom.xml

@@ -42,7 +42,7 @@
         <dependency>
             <groupId>com.github.dpaukov</groupId>
             <artifactId>combinatoricslib3</artifactId>
-            <version>3.3.0</version>
+            <version>${combinatoricslib3.version}</version>
          </dependency>
     </dependencies>
 
@@ -83,6 +83,7 @@
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
         <commons-codec.version>1.11</commons-codec.version>
         <guava.version>27.0.1-jre</guava.version>
+        <combinatoricslib3.version>3.3.0</combinatoricslib3.version>
     </properties>
 
 </project>

algorithms-miscellaneous-3/README.md

@@ -5,3 +5,5 @@
 - [Converting Between Roman and Arabic Numerals in Java](http://www.baeldung.com/java-convert-roman-arabic)
 - [Practical Java Examples of the Big O Notation](http://www.baeldung.com/java-algorithm-complexity)
 - [Checking If a List Is Sorted in Java](https://www.baeldung.com/java-check-if-list-sorted)
+- [Checking if a Java Graph has a Cycle](https://www.baeldung.com/java-graph-has-a-cycle)
+- [A Guide to the Folding Technique in Java](https://www.baeldung.com/folding-hashing-technique)

apache-avro/pom.xml

@@ -17,7 +17,7 @@
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
-            <version>4.10</version>
+            <version>${junit.version}</version>
             <scope>test</scope>
         </dependency>
         <dependency>

apache-olingo/olingo2/pom.xml

@@ -3,37 +3,28 @@
 	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>
-	<parent>
-		<groupId>org.springframework.boot</groupId>
-		<artifactId>spring-boot-starter-parent</artifactId>
-		<version>2.1.3.RELEASE</version>
-		<relativePath /> <!-- lookup parent from repository -->
-	</parent>
 	<groupId>org.baeldung.examples.olingo2</groupId>
 	<artifactId>olingo2-sample</artifactId>
 	<version>0.0.1-SNAPSHOT</version>
 	<name>olingo2-sample</name>
 	<description>Sample Olingo 2 Project</description>
 
-	<properties>
+    <parent>
-		<java.version>1.8</java.version>
+        <artifactId>parent-boot-2</artifactId>
-		<olingo2.version>2.0.11</olingo2.version>
+        <groupId>com.baeldung</groupId>
-	</properties>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-boot-2</relativePath>
+    </parent>
 
 	<dependencies>
-
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-jersey</artifactId>
 		</dependency>
-
-
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-data-jpa</artifactId>
 		</dependency>
-
-
 		<dependency>
 			<groupId>com.h2database</groupId>
 			<artifactId>h2</artifactId>
@@ -90,4 +81,8 @@
 		</plugins>
 	</build>
 
+	<properties>
+		<olingo2.version>2.0.11</olingo2.version>
+	</properties>
+
 </project>

apache-olingo/olingo2/src/test/java/org/baeldung/examples/olingo2/Olingo2SampleApplicationUnitTest.java

@@ -7,7 +7,7 @@ import org.springframework.test.context.junit4.SpringRunner;
 
 @RunWith(SpringRunner.class)
 @SpringBootTest
-public class Olingo2SampleApplicationTests {
+public class Olingo2SampleApplicationUnitTest {
 
 	@Test
 	public void contextLoads() {

apache-pulsar/pom.xml

@@ -7,6 +7,13 @@
     <version>0.0.1</version>
     <name>apache-pulsar</name>
 
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>..</relativePath>
+    </parent>
+
     <dependencies>
         <dependency>
             <groupId>org.apache.pulsar</groupId>

apache-pulsar/src/main/java/com/baeldung/ConsumerUnitTest.java

@@ -7,7 +7,7 @@ import org.apache.pulsar.client.api.Message;
 import org.apache.pulsar.client.api.PulsarClient;
 import org.apache.pulsar.client.api.SubscriptionType;
 
-public class ConsumerTest {
+public class ConsumerUnitTest {
 
     private static final String SERVICE_URL = "pulsar://localhost:6650";
     private static final String TOPIC_NAME = "test-topic";

apache-pulsar/src/main/java/com/baeldung/ProducerUnitTest.java

@@ -11,7 +11,7 @@ import org.apache.pulsar.client.api.PulsarClientException;
 import java.io.IOException;
 import java.util.stream.IntStream;
 
-public class ProducerTest {
+public class ProducerUnitTest {
 
     private static final String SERVICE_URL = "pulsar://localhost:6650";
     private static final String TOPIC_NAME = "test-topic";

apache-pulsar/src/main/java/com/baeldung/subscriptions/ExclusiveSubscriptionUnitTest.java

@@ -10,7 +10,7 @@ import org.apache.pulsar.client.api.SubscriptionType;
 
 import java.util.stream.IntStream;
 
-public class ExclusiveSubscriptionTest {
+public class ExclusiveSubscriptionUnitTest {
     private static final String SERVICE_URL = "pulsar://localhost:6650";
     private static final String TOPIC_NAME = "test-topic";
     private static final String SUBSCRIPTION_NAME = "test-subscription";

apache-pulsar/src/main/java/com/baeldung/subscriptions/FailoverSubscriptionUnitTest.java

@@ -11,7 +11,7 @@ import org.apache.pulsar.client.api.SubscriptionType;
 
 import java.util.stream.IntStream;
 
-public class FailoverSubscriptionTest {
+public class FailoverSubscriptionUnitTest {
     private static final String SERVICE_URL = "pulsar://localhost:6650";
     private static final String TOPIC_NAME = "failover-subscription-test-topic";
     private static final String SUBSCRIPTION_NAME = "test-subscription";

apache-spark/pom.xml

@@ -49,6 +49,7 @@
 			<version>${com.datastax.spark.spark-cassandra-connector-java.version}</version>
 		</dependency>
     </dependencies>
+
 	<build>
     	<plugins>
     	  	<plugin>
@@ -78,6 +79,7 @@
       		</plugin>
    		</plugins>
   	</build>
+
     <properties>
         <org.apache.spark.spark-core.version>2.3.0</org.apache.spark.spark-core.version>
         <org.apache.spark.spark-sql.version>2.3.0</org.apache.spark.spark-sql.version>

autovalue/README.md

@@ -1,3 +1,4 @@
 ### Relevant Articles:
 - [Introduction to AutoValue](http://www.baeldung.com/introduction-to-autovalue)
 - [Introduction to AutoFactory](http://www.baeldung.com/autofactory)
+- [Google AutoService](https://www.baeldung.com/google-autoservice)

aws/pom.xml

@@ -112,7 +112,6 @@
     </repositories>
 
     <properties>
-        <commons-io.version>2.5</commons-io.version>
         <aws-lambda-java-events.version>1.3.0</aws-lambda-java-events.version>
         <aws-lambda-java-core.version>1.1.0</aws-lambda-java-core.version>
         <gson.version>2.8.0</gson.version>

bootique/pom.xml

@@ -65,7 +65,6 @@
     <properties>
         <main.class>com.baeldung.bootique.App</main.class>
         <bootique-bom.version>0.23</bootique-bom.version>
-
         <maven-shade-plugin.version>2.4.3</maven-shade-plugin.version>
     </properties>
 

core-groovy-2/README.md

@@ -6,4 +6,5 @@
 - [Template Engines in Groovy](https://www.baeldung.com/groovy-template-engines)
 - [Groovy def Keyword](https://www.baeldung.com/groovy-def-keyword)
 - [Pattern Matching in Strings in Groovy](https://www.baeldung.com/groovy-pattern-matching)
-- [Working with XML in Groovy](https://www.baeldung.com/groovy-xml)
+- [Working with XML in Groovy](https://www.baeldung.com/groovy-xml)
+- [Integrating Groovy into Java Applications](https://www.baeldung.com/groovy-java-applications)

core-groovy-2/pom.xml

@@ -157,27 +157,24 @@
     </repositories>
 
     <pluginRepositories>
-                <pluginRepository>
+        <pluginRepository>
-                    <id>bintray</id>
+            <id>bintray</id>
-                    <name>Groovy Bintray</name>
+            <name>Groovy Bintray</name>
-                    <url>https://dl.bintray.com/groovy/maven</url>
+            <url>https://dl.bintray.com/groovy/maven</url>
-                    <releases>
+            <releases>
-                        <!-- avoid automatic updates -->
+                <!-- avoid automatic updates -->
-                        <updatePolicy>never</updatePolicy>
+                <updatePolicy>never</updatePolicy>
-                    </releases>
+            </releases>
-                    <snapshots>
+            <snapshots>
-                        <enabled>false</enabled>
+                <enabled>false</enabled>
-                    </snapshots>
+            </snapshots>
-                </pluginRepository>
+        </pluginRepository>
-            </pluginRepositories>
+    </pluginRepositories>
-
 
     <properties>
         <junit.platform.version>1.0.0</junit.platform.version>
         <hsqldb.version>2.4.0</hsqldb.version>
         <spock-core.version>1.1-groovy-2.4</spock-core.version>
-        <commons-lang3.version>3.9</commons-lang3.version>
-        <java.version>1.8</java.version>
         <maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>
         <logback.version>1.2.3</logback.version>
         <groovy.version>2.5.7</groovy.version>

core-groovy-2/src/main/groovy/com/baeldung/concatenate/Wonder.groovy

@@ -0,0 +1,52 @@
+package com.baeldung.concatenate
+
+class Wonder {
+
+    String numOfWonder = 'seven'
+
+    String operator_plus() {
+        return 'The ' + numOfWonder + ' wonders of the world'
+    }
+
+    String operator_left() {
+        return 'The ' << numOfWonder << ' wonders of ' << 'the world'
+    }
+
+    String interpolation_one() {
+        return "The $numOfWonder wonders of the world"
+
+    }
+
+    String interpolation_two() {
+        return "The ${numOfWonder} wonders of the world"
+    }
+
+    String multilineString() {
+        return """
+            There are $numOfWonder wonders of the world.
+            Can you name them all? 
+            1. The Great Pyramid of Giza
+            2. Hanging Gardens of Babylon
+            3. Colossus of Rhode
+            4. Lighthouse of Alexendra
+            5. Temple of Artemis
+            6. Status of Zeus at Olympia
+            7. Mausoleum at Halicarnassus
+        """
+    }
+
+    String method_concat() {
+        return 'The '.concat(numOfWonder).concat(' wonders of the world')
+
+    }
+
+    String method_builder() {
+        return new StringBuilder()
+                .append('The ').append(numOfWonder).append(' wonders of the world')
+    }
+
+    String method_buffer() {
+        return new StringBuffer()
+                .append('The ').append(numOfWonder).append(' wonders of the world')
+    }
+}

core-groovy-2/src/test/groovy/com/baeldung/concatenate/WonderUnitTest.groovy

@@ -0,0 +1,69 @@
+package com.baeldung.concatenate
+
+import org.junit.Before
+import org.junit.Test
+
+import static org.junit.Assert.*
+
+class WonderUnitTest {
+
+    static final String EXPECTED_SINGLE_LINE = "The seven wonders of the world"
+
+    Wonder wonder
+
+    @Before
+    void before() {
+        wonder = new Wonder()
+    }
+
+    @Test
+    void whenUsingOperatorPlus_thenConcatCorrectly() {
+        assertEquals(EXPECTED_SINGLE_LINE, wonder.operator_plus())
+    }
+
+    @Test
+    void whenUsingOperatorLeft_thenConcatCorrectly() {
+        assertEquals(EXPECTED_SINGLE_LINE, wonder.operator_left())
+    }
+
+    @Test
+    void whenUsingInterpolationOne_thenConcatCorrectly() {
+        assertEquals(EXPECTED_SINGLE_LINE, wonder.interpolation_one())
+    }
+
+    @Test
+    void whenUsingInterpolationTwo_thenConcatCorrectly() {
+        assertEquals(EXPECTED_SINGLE_LINE, wonder.interpolation_two())
+    }
+
+    @Test
+    void whenUsingMultiline_thenConcatCorrectly() {
+        def expectedMultiline = """
+            There are seven wonders of the world.
+            Can you name them all? 
+            1. The Great Pyramid of Giza
+            2. Hanging Gardens of Babylon
+            3. Colossus of Rhode
+            4. Lighthouse of Alexendra
+            5. Temple of Artemis
+            6. Status of Zeus at Olympia
+            7. Mausoleum at Halicarnassus
+        """
+        assertEquals(expectedMultiline, wonder.multilineString())
+    }
+
+    @Test
+    void whenUsingMethodConcat_thenConcatCorrectly() {
+        assertEquals(EXPECTED_SINGLE_LINE, wonder.method_concat())
+    }
+
+    @Test
+    void whenUsingMethodBuilder_thenConcatCorrectly() {
+        assertEquals(EXPECTED_SINGLE_LINE, wonder.method_builder())
+    }
+
+    @Test
+    void whenUsingMethodBuffer_thenConcatCorrectly() {
+        assertEquals(EXPECTED_SINGLE_LINE, wonder.method_buffer())
+    }
+}

core-java-modules/README.md

@@ -3,3 +3,4 @@
 - [Multi-Module Maven Application with Java Modules](https://www.baeldung.com/maven-multi-module-project-java-jpms)
 - [Guide to Java FileChannel](https://www.baeldung.com/java-filechannel)
 - [Understanding the NumberFormatException in Java](https://www.baeldung.com/java-number-format-exception)
+- [Will an Error Be Caught by Catch Block in Java?](https://www.baeldung.com/java-error-catch)

core-java-modules/core-java-10/README.md

@@ -5,3 +5,4 @@
 - [Guide to Java 10](http://www.baeldung.com/java-10-overview)
 - [Copy a List to Another List in Java](http://www.baeldung.com/java-copy-list-to-another)
 - [Deep Dive Into the New Java JIT Compiler – Graal](https://www.baeldung.com/graal-java-jit-compiler)
+- [Copying Sets in Java](https://www.baeldung.com/java-copy-sets)

core-java-modules/core-java-11/src/main/java/com/baeldung/predicate/not/README.md

@@ -0,0 +1,3 @@
+## Relevant articles:
+
+- [Negate a Predicate Method Reference with Java 11](https://www.baeldung.com/java-negate-predicate-method-reference)

core-java-modules/core-java-12/README.md

@@ -0,0 +1,3 @@
+## Relevant articles:
+
+- [String API Updates in Java 12](https://www.baeldung.com/java12-string-api)

core-java-modules/core-java-8-2/README.md

@@ -6,3 +6,4 @@
 - [Anonymous Classes in Java](http://www.baeldung.com/)
 - [How to Delay Code Execution in Java](https://www.baeldung.com/java-delay-code-execution)
 - [Run JAR Application With Command Line Arguments](https://www.baeldung.com/java-run-jar-with-arguments)
+- [Java 8 Stream skip() vs limit()](https://www.baeldung.com/java-stream-skip-vs-limit)

core-java-modules/core-java-8-2/pom.xml

@@ -9,7 +9,6 @@
     <name>core-java-8-2</name>
     <packaging>jar</packaging>
 
-
     <parent>
         <groupId>com.baeldung</groupId>
         <artifactId>parent-java</artifactId>
@@ -17,19 +16,18 @@
         <relativePath>../../parent-java</relativePath>
     </parent>
 
-    <properties>
-        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <maven.compiler.source>1.8</maven.compiler.source>
-        <maven.compiler.target>1.8</maven.compiler.target>
-        <icu.version>64.2</icu.version>
-    </properties>
-
     <dependencies>
         <dependency>
             <groupId>com.ibm.icu</groupId>
             <artifactId>icu4j</artifactId>
             <version>${icu.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
@@ -44,6 +42,13 @@
                 </configuration>
             </plugin>
         </plugins>
-
     </build>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+        <icu.version>64.2</icu.version>
+        <assertj.version>3.12.2</assertj.version>
+    </properties>
 </project>

core-java-modules/core-java-8-2/src/test/java/com/baeldung/bifunction/BiFunctionalInterfacesUnitTest.java

@@ -0,0 +1,164 @@
+package com.baeldung.bifunction;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+import java.util.function.BiFunction;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class BiFunctionalInterfacesUnitTest {
+    @Test
+    public void givenStreamValues_whenMappedToNewValues() {
+        List<String> mapped = Stream.of("hello", "world")
+                .map(word -> word + "!")
+                .collect(Collectors.toList());
+
+        assertThat(mapped).containsExactly("hello!", "world!");
+    }
+
+    @Test
+    public void givenStreamValues_whenReducedWithPrefixingOperation() {
+        String result = Stream.of("hello", "world")
+                .reduce("", (a, b) -> b + "-" + a);
+
+        assertThat(result).isEqualTo("world-hello-");
+    }
+
+    @Test
+    public void givenStreamValues_whenReducedWithPrefixingLambda_thenHasNoTrailingDash() {
+        String result = Stream.of("hello", "world")
+                .reduce("", (a, b) -> combineWithoutTrailingDash(a, b));
+
+        assertThat(result).isEqualTo("world-hello");
+    }
+
+    private String combineWithoutTrailingDash(String a, String b) {
+        if (a.isEmpty()) {
+            return b;
+        }
+        return b + "-" + a;
+    }
+
+    @Test
+    public void givenStreamValues_whenReducedWithPrefixingMethodReference_thenHasNoTrailingDash() {
+        String result = Stream.of("hello", "world")
+                .reduce("", this::combineWithoutTrailingDash);
+
+        assertThat(result).isEqualTo("world-hello");
+    }
+
+    @Test
+    public void givenTwoLists_whenCombined() {
+        List<String> list1 = Arrays.asList("a", "b", "c");
+        List<Integer> list2 = Arrays.asList(1, 2, 3);
+
+        List<String> result = new ArrayList<>();
+        for (int i=0; i < list1.size(); i++) {
+            result.add(list1.get(i) + list2.get(i));
+        }
+
+        assertThat(result).containsExactly("a1", "b2", "c3");
+    }
+
+    @Test
+    public void givenTwoLists_whenCombinedWithGeneralPurposeCombiner() {
+        List<String> list1 = Arrays.asList("a", "b", "c");
+        List<Integer> list2 = Arrays.asList(1, 2, 3);
+
+        List<String> result = listCombiner(list1, list2, (a, b) -> a + b);
+
+        assertThat(result).containsExactly("a1", "b2", "c3");
+    }
+
+    private static <T, U, R> List<R> listCombiner(List<T> list1,
+                                                  List<U> list2,
+                                                  BiFunction<T, U, R> combiner) {
+        List<R> result = new ArrayList<>();
+        for (int i = 0; i < list1.size(); i++) {
+            result.add(combiner.apply(list1.get(i), list2.get(i)));
+        }
+        return result;
+    }
+
+    @Test
+    public void givenTwoLists_whenComparedWithCombiningFunction() {
+        List<Double> list1 = Arrays.asList(1.0d, 2.1d, 3.3d);
+        List<Float> list2 = Arrays.asList(0.1f, 0.2f, 4f);
+
+        // algorithm to determine if the value in list1 > value in list 2
+        List<Boolean> result = listCombiner(list1, list2, (a, b) -> a > b);
+
+        assertThat(result).containsExactly(true, true, false);
+    }
+
+    @Test
+    public void givenTwoLists_whenComparedWithCombiningFunctionByMethodReference() {
+        List<Double> list1 = Arrays.asList(1.0d, 2.1d, 3.3d);
+        List<Float> list2 = Arrays.asList(0.1f, 0.2f, 4f);
+
+        // algorithm to determine if the value in list1 > value in list 2
+        List<Boolean> result = listCombiner(list1, list2, this::firstIsGreaterThanSecond);
+
+        assertThat(result).containsExactly(true, true, false);
+    }
+
+    private boolean firstIsGreaterThanSecond(Double a, Float b) {
+        return a > b;
+    }
+
+    @Test
+    public void givenTwoLists_whenComparedForEqualityByCombiningFunction() {
+        List<Float> list1 = Arrays.asList(0.1f, 0.2f, 4f);
+        List<Float> list2 = Arrays.asList(0.1f, 0.2f, 4f);
+
+        List<Boolean> result = listCombiner(list1, list2, (a, b) -> a.equals(b));
+
+        assertThat(result).containsExactly(true, true, true);
+    }
+
+    @Test
+    public void givenTwoLists_whenComparedForEqualityByCombiningFunctionWithMethodReference() {
+        List<Float> list1 = Arrays.asList(0.1f, 0.2f, 4f);
+        List<Float> list2 = Arrays.asList(0.1f, 0.2f, 4f);
+
+        List<Boolean> result = listCombiner(list1, list2, Float::equals);
+
+        assertThat(result).containsExactly(true, true, true);
+    }
+
+    @Test
+    public void givenTwoLists_whenComparedWithCombiningFunctionWithCompareTo() {
+        List<Double> list1 = Arrays.asList(1.0d, 2.1d, 3.3d);
+        List<Double> list2 = Arrays.asList(0.1d, 0.2d, 4d);
+
+        List<Integer> result = listCombiner(list1, list2, Double::compareTo);
+
+        assertThat(result).containsExactly(1, 1, -1);
+    }
+
+    /**
+     * Allows you to to pass in a lambda or method reference and then
+     * get access to the BiFunction it is meant to become
+     */
+    private static <T, U, R> BiFunction<T, U, R> asBiFunction(BiFunction<T, U, R> function) {
+        return function;
+    }
+
+    @Test
+    public void givenTwoLists_whenComparedWithCombiningFunctionWithComposedBiFunction() {
+        List<Double> list1 = Arrays.asList(1.0d, 2.1d, 3.3d);
+        List<Double> list2 = Arrays.asList(0.1d, 0.2d, 4d);
+
+        List<Boolean> result = listCombiner(list1, list2,
+                asBiFunction(Double::compareTo)
+                    .andThen(i -> i > 0));
+
+        assertThat(result).containsExactly(true, true, false);
+    }
+}

core-java-modules/core-java-8/README.md

@@ -40,3 +40,4 @@
 - [Java 8 Predicate Chain](https://www.baeldung.com/java-predicate-chain)
 - [Method References in Java](https://www.baeldung.com/java-method-references)
 - [Creating a Custom Annotation in Java](https://www.baeldung.com/java-custom-annotation)
+- [The Difference Between Collection.stream().forEach() and Collection.forEach()](https://www.baeldung.com/java-collection-stream-foreach)

core-java-modules/core-java-8/pom.xml

@@ -175,7 +175,6 @@
 
     <properties>
         <!-- util -->
-        <commons-lang3.version>3.5</commons-lang3.version>
         <commons-math3.version>3.6.1</commons-math3.version>
         <commons-collections4.version>4.1</commons-collections4.version>
         <collections-generic.version>4.01</collections-generic.version>

core-java-modules/core-java-8/src/test/java/com/baeldung/java8/optional/OptionalUnitTest.java

@@ -259,4 +259,15 @@ public class OptionalUnitTest {
         LOG.debug("Getting default value...");
         return "Default Value";
     }
+    
+//    Uncomment code when code base is compatiable with Java 11     
+//    @Test
+//    public void givenAnEmptyOptional_thenIsEmptyBehavesAsExpected() {
+//        Optional<String> opt = Optional.of("Baeldung");
+//        assertFalse(opt.isEmpty());
+//     
+//        opt = Optional.ofNullable(null);
+//        assertTrue(opt.isEmpty());
+//    }
+
 }

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

@@ -389,7 +389,7 @@
     <properties>
 
         <!-- util -->
-        <commons-lang3.version>3.8.1</commons-lang3.version>
+        <commons-lang3.version>3.9</commons-lang3.version>
         
         <jmh-core.version>1.19</jmh-core.version>
         <jmh-generator-annprocess.version>1.19</jmh-generator-annprocess.version>

core-java-modules/core-java-arrays/src/main/java/com/baeldung/array/JaggedArray.java

@@ -1,49 +0,0 @@
-package com.baeldung.array;
-
-import java.util.Arrays;
-import java.util.Scanner;
-
-public class JaggedArray {
-
-    int[][] shortHandFormInitialization() {
-        int[][] jaggedArr = { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } };
-        return jaggedArr;
-    }
-
-    int[][] declarationAndThenInitialization() {
-        int[][] jaggedArr = new int[3][];
-        jaggedArr[0] = new int[] { 1, 2 };
-        jaggedArr[1] = new int[] { 3, 4, 5 };
-        jaggedArr[2] = new int[] { 6, 7, 8, 9 };
-        return jaggedArr;
-    }
-
-    int[][] declarationAndThenInitializationUsingUserInputs() {
-        int[][] jaggedArr = new int[3][];
-        jaggedArr[0] = new int[2];
-        jaggedArr[1] = new int[3];
-        jaggedArr[2] = new int[4];
-        initializeElements(jaggedArr);
-        return jaggedArr;
-    }
-
-    void initializeElements(int[][] jaggedArr) {
-        Scanner sc = new Scanner(System.in);
-        for (int outer = 0; outer < jaggedArr.length; outer++) {
-            for (int inner = 0; inner < jaggedArr[outer].length; inner++) {
-                jaggedArr[outer][inner] = sc.nextInt();
-            }
-        }
-    }
-
-    void printElements(int[][] jaggedArr) {
-        for (int index = 0; index < jaggedArr.length; index++) {
-            System.out.println(Arrays.toString(jaggedArr[index]));
-        }
-    }
-
-    int[] getElementAtGivenIndex(int[][] jaggedArr, int index) {
-        return jaggedArr[index];
-    }
-
-}

core-java-modules/core-java-arrays/src/main/java/com/baeldung/array/MultiDimensionalArray.java

@@ -0,0 +1,83 @@
+package com.baeldung.array;
+
+import java.util.Arrays;
+import java.util.Scanner;
+
+public class MultiDimensionalArray {
+
+    int[][] shortHandFormInitialization() {
+        int[][] multiDimensionalArray = { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } };
+        return multiDimensionalArray;
+    }
+
+    int[][] declarationAndThenInitialization() {
+        int[][] multiDimensionalArray = new int[3][];
+        multiDimensionalArray[0] = new int[] { 1, 2 };
+        multiDimensionalArray[1] = new int[] { 3, 4, 5 };
+        multiDimensionalArray[2] = new int[] { 6, 7, 8, 9 };
+        return multiDimensionalArray;
+    }
+
+    int[][] declarationAndThenInitializationUsingUserInputs() {
+        int[][] multiDimensionalArray = new int[3][];
+        multiDimensionalArray[0] = new int[2];
+        multiDimensionalArray[1] = new int[3];
+        multiDimensionalArray[2] = new int[4];
+        initializeElements(multiDimensionalArray);
+        return multiDimensionalArray;
+    }
+
+    void initializeElements(int[][] multiDimensionalArray) {
+        Scanner sc = new Scanner(System.in);
+        for (int outer = 0; outer < multiDimensionalArray.length; outer++) {
+            for (int inner = 0; inner < multiDimensionalArray[outer].length; inner++) {
+                multiDimensionalArray[outer][inner] = sc.nextInt();
+            }
+        }
+    }
+
+    void initialize2DArray(int[][] multiDimensionalArray) {
+        for (int[] array : multiDimensionalArray) {
+            Arrays.fill(array, 7);
+        }
+    }
+
+    void printElements(int[][] multiDimensionalArray) {
+        for (int index = 0; index < multiDimensionalArray.length; index++) {
+            System.out.println(Arrays.toString(multiDimensionalArray[index]));
+        }
+    }
+
+    int[] getElementAtGivenIndex(int[][] multiDimensionalArray, int index) {
+        return multiDimensionalArray[index];
+    }
+
+    int[] findLengthOfElements(int[][] multiDimensionalArray) {
+        int[] arrayOfLengths = new int[multiDimensionalArray.length];
+        for (int i = 0; i < multiDimensionalArray.length; i++) {
+            arrayOfLengths[i] = multiDimensionalArray[i].length;
+        }
+        return arrayOfLengths;
+    }
+
+    Integer[] findLengthOfElements(Integer[][] multiDimensionalArray) {
+        return Arrays.stream(multiDimensionalArray)
+          .map(array -> array.length)
+          .toArray(Integer[]::new);
+    }
+
+    int[][] copy2DArray(int[][] arrayOfArrays) {
+        int[][] copied2DArray = new int[arrayOfArrays.length][];
+        for (int i = 0; i < arrayOfArrays.length; i++) {
+            int[] array = arrayOfArrays[i];
+            copied2DArray[i] = Arrays.copyOf(array, array.length);
+        }
+        return copied2DArray;
+    }
+
+    Integer[][] copy2DArray(Integer[][] arrayOfArrays) {
+        return Arrays.stream(arrayOfArrays)
+          .map(array -> Arrays.copyOf(array, array.length))
+          .toArray(Integer[][]::new);
+    }
+}

core-java-modules/core-java-arrays/src/main/java/com/baeldung/array/RemoveElementFromAnArray.java

@@ -0,0 +1,27 @@
+package com.baeldung.array;
+
+import org.apache.commons.lang3.ArrayUtils;
+
+public class RemoveElementFromAnArray {
+
+    public int[] removeAnElementWithAGivenIndex(int[] array, int index) {
+        return ArrayUtils.remove(array, index);
+    }
+
+    public int[] removeAllElementsWithGivenIndices(int[] array, int... indicies) {
+        return ArrayUtils.removeAll(array, indicies);
+    }
+
+    public int[] removeFirstOccurrenceOfGivenElement(int[] array, int element) {
+        return ArrayUtils.removeElement(array, element);
+    }
+
+    public int[] removeAllGivenElements(int[] array, int... elements) {
+        return ArrayUtils.removeElements(array, elements);
+    }
+
+    public int[] removeAllOccurrencesOfAGivenElement(int[] array, int element) {
+        return ArrayUtils.removeAllOccurences(array, element);
+    }
+
+}

core-java-modules/core-java-arrays/src/main/java/com/baeldung/array/SortedArrayChecker.java

@@ -0,0 +1,71 @@
+package com.baeldung.array;
+
+import com.baeldung.arraycopy.model.Employee;
+
+public class SortedArrayChecker {
+    boolean isSorted(int[] array, int length) {
+        if (array == null || length < 2)
+            return true;
+
+        if (array[length - 2] > array[length - 1])
+            return false;
+
+        return isSorted(array, length - 1);
+    }
+
+    boolean isSorted(int[] array) {
+        for (int i = 0; i < array.length - 1; i++) {
+            if (array[i] > array[i + 1])
+                return false;
+        }
+
+        return true;
+    }
+
+    boolean isSorted(String[] array, int length) {
+        if (array == null || length < 2)
+            return true;
+
+        if (array[length - 2].compareTo(array[length - 1]) > 0)
+            return false;
+
+        return isSorted(array, length - 1);
+    }
+
+boolean isSorted(String[] array) {
+    for (int i = 0; i < array.length - 1; ++i) {
+        if (array[i].compareTo(array[i + 1]) > 0)
+            return false;
+    }
+
+    return true;
+}
+
+    boolean isSortedByName(Employee[] array) {
+        for (int i = 0; i < array.length - 1; ++i) {
+            if (array[i].getName().compareTo(array[i + 1].getName()) > 0)
+                return false;
+        }
+
+        return true;
+    }
+
+boolean isSortedByAge(Employee[] array) {
+    for (int i = 0; i < array.length - 1; ++i) {
+        if (array[i].getAge() > (array[i + 1].getAge()))
+            return false;
+    }
+
+    return true;
+}
+
+    boolean isSortedByAge(Employee[] array, int length) {
+        if (array == null || length < 2)
+            return true;
+
+        if (array[length - 2].getAge() > array[length - 1].getAge())
+            return false;
+
+        return isSortedByAge(array, length - 1);
+    }
+}

core-java-modules/core-java-arrays/src/main/java/com/baeldung/arraycopy/model/Employee.java

@@ -6,6 +6,7 @@ public class Employee implements Serializable {
     private static final long serialVersionUID = -2454619097207585825L;
     private int id;
     private String name;
+    private int age;
 
     public Employee() {
     }
@@ -15,10 +16,24 @@ public class Employee implements Serializable {
         this.name = name;
     }
 
+    public Employee(int id, String name, int age) {
+        this.id = id;
+        this.name = name;
+        this.age = age;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
     public int getId() {
         return id;
     }
 
+    public void setAge(int age) {
+        this.age = age;
+    }
+
     public void setId(int id) {
         this.id = id;
     }

core-java-modules/core-java-arrays/src/test/java/com/baeldung/array/JaggedArrayUnitTest.java

@@ -1,53 +0,0 @@
-package com.baeldung.array;
-
-import static org.junit.Assert.assertArrayEquals;
-import static org.junit.Assert.assertEquals;
-
-import java.io.ByteArrayInputStream;
-import java.io.ByteArrayOutputStream;
-import java.io.InputStream;
-import java.io.PrintStream;
-
-import org.junit.Test;
-
-public class JaggedArrayUnitTest {
-
-    private JaggedArray obj = new JaggedArray();
-
-    @Test
-    public void whenInitializedUsingShortHandForm_thenCorrect() {
-        assertArrayEquals(new int[][] { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } }, obj.shortHandFormInitialization());
-    }
-
-    @Test
-    public void whenInitializedWithDeclarationAndThenInitalization_thenCorrect() {
-        assertArrayEquals(new int[][] { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } }, obj.declarationAndThenInitialization());
-    }
-
-    @Test
-    public void whenInitializedWithDeclarationAndThenInitalizationUsingUserInputs_thenCorrect() {
-        InputStream is = new ByteArrayInputStream("1 2 3 4 5 6 7 8 9".getBytes());
-        System.setIn(is);
-        assertArrayEquals(new int[][] { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } }, obj.declarationAndThenInitializationUsingUserInputs());
-        System.setIn(System.in);
-    }
-
-    @Test
-    public void givenJaggedArrayAndAnIndex_thenReturnArrayAtGivenIndex() {
-        int[][] jaggedArr = { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } };
-        assertArrayEquals(new int[] { 1, 2 }, obj.getElementAtGivenIndex(jaggedArr, 0));
-        assertArrayEquals(new int[] { 3, 4, 5 }, obj.getElementAtGivenIndex(jaggedArr, 1));
-        assertArrayEquals(new int[] { 6, 7, 8, 9 }, obj.getElementAtGivenIndex(jaggedArr, 2));
-    }
-
-    @Test
-    public void givenJaggedArray_whenUsingArraysAPI_thenVerifyPrintedElements() {
-        int[][] jaggedArr = { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } };
-        ByteArrayOutputStream outContent = new ByteArrayOutputStream();
-        System.setOut(new PrintStream(outContent));
-        obj.printElements(jaggedArr);
-        assertEquals("[1, 2][3, 4, 5][6, 7, 8, 9]", outContent.toString().replace("\r", "").replace("\n", ""));
-        System.setOut(System.out);
-    }
-
-}

core-java-modules/core-java-arrays/src/test/java/com/baeldung/array/MultiDimensionalArrayUnitTest.java

@@ -0,0 +1,86 @@
+package com.baeldung.array;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.io.PrintStream;
+
+import org.junit.Test;
+
+public class MultiDimensionalArrayUnitTest {
+
+    private MultiDimensionalArray obj = new MultiDimensionalArray();
+
+    @Test
+    public void whenInitializedUsingShortHandForm_thenCorrect() {
+        assertArrayEquals(new int[][] { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } }, obj.shortHandFormInitialization());
+    }
+
+    @Test
+    public void whenInitializedWithDeclarationAndThenInitalization_thenCorrect() {
+        assertArrayEquals(new int[][] { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } }, obj.declarationAndThenInitialization());
+    }
+
+    @Test
+    public void whenInitializedWithDeclarationAndThenInitalizationUsingUserInputs_thenCorrect() {
+        InputStream is = new ByteArrayInputStream("1 2 3 4 5 6 7 8 9".getBytes());
+        System.setIn(is);
+        assertArrayEquals(new int[][] { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } }, obj.declarationAndThenInitializationUsingUserInputs());
+        System.setIn(System.in);
+    }
+
+    @Test
+    public void givenMultiDimensionalArrayAndAnIndex_thenReturnArrayAtGivenIndex() {
+        int[][] multiDimensionalArr = { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } };
+        assertArrayEquals(new int[] { 1, 2 }, obj.getElementAtGivenIndex(multiDimensionalArr, 0));
+        assertArrayEquals(new int[] { 3, 4, 5 }, obj.getElementAtGivenIndex(multiDimensionalArr, 1));
+        assertArrayEquals(new int[] { 6, 7, 8, 9 }, obj.getElementAtGivenIndex(multiDimensionalArr, 2));
+    }
+
+    @Test
+    public void givenMultiDimensionalArray_whenUsingArraysAPI_thenVerifyPrintedElements() {
+        int[][] multiDimensionalArr = { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } };
+        ByteArrayOutputStream outContent = new ByteArrayOutputStream();
+        System.setOut(new PrintStream(outContent));
+        obj.printElements(multiDimensionalArr);
+        assertEquals("[1, 2][3, 4, 5][6, 7, 8, 9]", outContent.toString().replace("\r", "").replace("\n", ""));
+        System.setOut(System.out);
+    }
+
+    @Test
+    public void givenMultiDimensionalArray_whenUsingArraysFill_thenVerifyInitialize2DArray() {
+        int[][] multiDimensionalArr = new int[3][];
+        multiDimensionalArr[0] = new int[2];
+        multiDimensionalArr[1] = new int[3];
+        multiDimensionalArr[2] = new int[4];
+        obj.initialize2DArray(multiDimensionalArr);
+        assertArrayEquals(new int[][] {{7,7}, {7,7,7}, {7,7,7,7}}, multiDimensionalArr);
+    }
+    
+    @Test
+    public void givenMultiDimensionalArray_whenUsingIteration_thenVerifyFindLengthOfElements() {
+        int[][] multiDimensionalArr = { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } };
+        assertArrayEquals(new int[]{2,3,4}, obj.findLengthOfElements(multiDimensionalArr));
+    }
+    
+    @Test
+    public void givenMultiDimensionalArray_whenUsingArraysStream_thenVerifyFindLengthOfElements() {
+        Integer[][] multiDimensionalArr = { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } };
+        assertArrayEquals(new Integer[]{2,3,4}, obj.findLengthOfElements(multiDimensionalArr));
+    }
+    
+    @Test
+    public void givenMultiDimensionalArray_whenUsingArraysCopyOf_thenVerifyCopy2DArray() {
+        int[][] multiDimensionalArr = { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } };
+        assertArrayEquals(multiDimensionalArr, obj.copy2DArray(multiDimensionalArr));
+    }
+    
+    @Test
+    public void givenMultiDimensionalArray_whenUsingArraysStream_thenVerifyCopy2DArray() {
+        Integer[][] multiDimensionalArr = { { 1, 2 }, { 3, 4, 5 }, { 6, 7, 8, 9 } };
+        assertArrayEquals(multiDimensionalArr, obj.copy2DArray(multiDimensionalArr));
+    }
+}

core-java-modules/core-java-arrays/src/test/java/com/baeldung/array/RemoveElementFromAnArrayUnitTest.java

@@ -0,0 +1,85 @@
+package com.baeldung.array;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.apache.commons.lang3.ArrayUtils;
+import org.junit.jupiter.api.Test;
+
+class RemoveElementFromAnArrayUnitTest {
+
+    private final RemoveElementFromAnArray sut = new RemoveElementFromAnArray();
+    private final int[] inputArray = new int[] { 40, 10, 20, 30, 40, 50 };
+
+    @Test
+    void testRemoveAnElementWithAGivenIndex() {
+        int index = 2;
+        int[] modifiedArray = sut.removeAnElementWithAGivenIndex(inputArray, index);
+
+        assertFalse(ArrayUtils.contains(modifiedArray, inputArray[index]));
+    }
+
+    @Test
+    void testRemoveAllElementsWithGivenIndices() {
+        int first = 0;
+        int last = inputArray.length - 1;
+        int[] modifiedArray = sut.removeAllElementsWithGivenIndices(inputArray, first, last);
+
+        assertFalse(ArrayUtils.contains(modifiedArray, inputArray[first]) && ArrayUtils.contains(modifiedArray, inputArray[last]));
+    }
+
+    @Test
+    void testRemoveElement_WhenArrayIsNull_ThrowsIndexOutOfBoundEx() {
+        int index = 2;
+
+        assertThrows(IndexOutOfBoundsException.class, () -> {
+            sut.removeAnElementWithAGivenIndex(null, index);
+        });
+
+        assertThrows(IndexOutOfBoundsException.class, () -> {
+            sut.removeAllElementsWithGivenIndices(null, index);
+        });
+    }
+
+    @Test
+    void testRemoveFirstOccurrenceOfGivenElement() {
+        int element = 40;
+        int[] modifiedArray = sut.removeFirstOccurrenceOfGivenElement(inputArray, element);
+
+        int indexInInputArray = ArrayUtils.indexOf(inputArray, element);
+        int indexInModifiedArray = ArrayUtils.indexOf(modifiedArray, element);
+        assertFalse(indexInInputArray == indexInModifiedArray);
+    }
+
+    @Test
+    void testRemoveAllGivenElements() {
+        int duplicateElement = 40;
+        int[] elements = new int[] { duplicateElement, 10, 50 };
+        int[] modifiedArray = sut.removeAllGivenElements(inputArray, elements);
+
+        assertTrue(ArrayUtils.contains(modifiedArray, duplicateElement));
+        assertFalse(ArrayUtils.contains(modifiedArray, elements[1]));
+        assertFalse(ArrayUtils.contains(modifiedArray, elements[2]));
+    }
+
+    @Test
+    void testRemoveAllOccurrencesOfAGivenElement() {
+        int element = 40;
+        int[] modifiedArray = sut.removeAllOccurrencesOfAGivenElement(inputArray, element);
+
+        assertFalse(ArrayUtils.contains(modifiedArray, element));
+    }
+
+    @Test
+    void testRemoveElement_WhenArrayIsNull_ReturnsNull() {
+        int element = 20;
+
+        assertEquals(null, sut.removeFirstOccurrenceOfGivenElement(null, element));
+        assertEquals(null, sut.removeAllGivenElements(null, element));
+        assertEquals(null, sut.removeAllOccurrencesOfAGivenElement(null, element));
+
+    }
+
+}

core-java-modules/core-java-arrays/src/test/java/com/baeldung/array/SortedArrayCheckerUnitTest.java

@@ -0,0 +1,73 @@
+package com.baeldung.array;
+
+import com.baeldung.arraycopy.model.Employee;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class SortedArrayCheckerUnitTest {
+
+    private static final int[] INTEGER_SORTED = {1, 3, 5, 7, 9};
+    private static final int[] INTEGER_NOT_SORTED = {1, 3, 11, 7};
+
+    private static final String[] STRING_SORTED = {"abc", "cde", "fgh"};
+    private static final String[] STRING_NOT_SORTED = {"abc", "fgh", "cde", "ijk"};
+
+    private final Employee[] EMPLOYEES_SORTED_BY_NAME = {
+            new Employee(1, "Carlos", 26),
+            new Employee(2, "Daniel", 31),
+            new Employee(3, "Marta", 27)};
+
+    private final Employee[] EMPLOYEES_NOT_SORTED_BY_NAME = {
+            new Employee(1, "Daniel", 31),
+            new Employee(2, "Carlos", 26),
+            new Employee(3, "Marta", 27)};
+
+    private final Employee[] EMPLOYEES_SORTED_BY_AGE = {
+            new Employee(1, "Carlos", 26),
+            new Employee(2, "Marta", 27),
+            new Employee(3, "Daniel", 31)};
+
+    private final Employee[] EMPLOYEES_NOT_SORTED_BY_AGE = {
+            new Employee(1, "Marta", 27),
+            new Employee(2, "Carlos", 26),
+            new Employee(3, "Daniel", 31)};
+
+    private SortedArrayChecker sortedArrayChecker;
+
+    @Before
+    public void setup() {
+        sortedArrayChecker = new SortedArrayChecker();
+    }
+
+    @Test
+    public void givenIntegerArray_thenReturnIfItIsSortedOrNot() {
+        assertThat(sortedArrayChecker.isSorted(INTEGER_SORTED)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSorted(INTEGER_NOT_SORTED)).isEqualTo(false);
+
+        assertThat(sortedArrayChecker.isSorted(INTEGER_SORTED, INTEGER_SORTED.length)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSorted(INTEGER_NOT_SORTED, INTEGER_NOT_SORTED.length)).isEqualTo(false);
+    }
+
+    @Test
+    public void givenStringArray_thenReturnIfItIsSortedOrNot() {
+        assertThat(sortedArrayChecker.isSorted(STRING_SORTED)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSorted(STRING_NOT_SORTED)).isEqualTo(false);
+
+        assertThat(sortedArrayChecker.isSorted(STRING_SORTED, STRING_SORTED.length)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSorted(STRING_NOT_SORTED, STRING_NOT_SORTED.length)).isEqualTo(false);
+    }
+
+    @Test
+    public void givenEmployeeArray_thenReturnIfItIsSortedOrNot() {
+        assertThat(sortedArrayChecker.isSortedByName(EMPLOYEES_SORTED_BY_NAME)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSortedByName(EMPLOYEES_NOT_SORTED_BY_NAME)).isEqualTo(false);
+
+        assertThat(sortedArrayChecker.isSortedByAge(EMPLOYEES_SORTED_BY_AGE)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSortedByAge(EMPLOYEES_NOT_SORTED_BY_AGE)).isEqualTo(false);
+
+        assertThat(sortedArrayChecker.isSortedByAge(EMPLOYEES_SORTED_BY_AGE, EMPLOYEES_SORTED_BY_AGE.length)).isEqualTo(true);
+        assertThat(sortedArrayChecker.isSortedByAge(EMPLOYEES_NOT_SORTED_BY_AGE, EMPLOYEES_NOT_SORTED_BY_AGE.length)).isEqualTo(false);
+    }
+}

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

@@ -10,3 +10,4 @@
 - [Initializing HashSet at the Time of Construction](http://www.baeldung.com/java-initialize-hashset)
 - [Guide to EnumSet](https://www.baeldung.com/java-enumset)
 - [Set Operations in Java](https://www.baeldung.com/java-set-operations)
+- [Copying Sets in Java](https://www.baeldung.com/java-copy-sets)

core-java-modules/core-java-collections-set/pom.xml

@@ -14,30 +14,31 @@
     </parent>
 
     <dependencies>
-    <dependency>
+        <dependency>
-        <groupId>com.google.guava</groupId>
+            <groupId>com.google.guava</groupId>
-        <artifactId>guava</artifactId>
+            <artifactId>guava</artifactId>
-        <version>${guava.version}</version>
+            <version>${guava.version}</version>
-    </dependency>
+        </dependency>
-    <dependency>
+        <dependency>
-        <groupId>org.apache.commons</groupId>
+            <groupId>org.apache.commons</groupId>
-        <artifactId>commons-collections4</artifactId>
+            <artifactId>commons-collections4</artifactId>
-        <version>${commons-collections4.version}</version>
+            <version>${commons-collections4.version}</version>
-    </dependency>
+        </dependency>
-    <dependency>
+        <dependency>
-        <groupId>com.google.code.gson</groupId>
+            <groupId>com.google.code.gson</groupId>
-        <artifactId>gson</artifactId>
+            <artifactId>gson</artifactId>
-        <version>2.8.5</version>
+            <version>${gson.version}</version>
-    </dependency>
+        </dependency>
-    <dependency>
+        <dependency>
-        <groupId>commons-lang</groupId>
+            <groupId>commons-lang</groupId>
-        <artifactId>commons-lang</artifactId>
+            <artifactId>commons-lang</artifactId>
-        <version>2.6</version>
+            <version>${commons-lang.version}</version>
-    </dependency>
+        </dependency>
     </dependencies>
 
     <properties>
         <commons-collections4.version>4.3</commons-collections4.version>
         <guava.version>27.1-jre</guava.version>
+        <gson.version>2.8.5</gson.version>
     </properties>
 </project>

core-java-modules/core-java-concurrency-advanced/pom.xml

@@ -72,7 +72,6 @@
     <properties>
         <!-- util -->
         <guava.version>21.0</guava.version>
-        <commons-lang3.version>3.5</commons-lang3.version>
         <commons-math3.version>3.6.1</commons-math3.version>
         <commons-collections4.version>4.1</commons-collections4.version>
         <collections-generic.version>4.01</collections-generic.version>

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

@@ -17,3 +17,4 @@
 - [Runnable vs. Callable in Java](http://www.baeldung.com/java-runnable-callable)
 - [What is Thread-Safety and How to Achieve it?](https://www.baeldung.com/java-thread-safety)
 - [How to Start a Thread in Java](https://www.baeldung.com/java-start-thread)
+- [How to Delay Code Execution in Java](https://www.baeldung.com/java-delay-code-execution)

core-java-modules/core-java-concurrency-basic/pom.xml

@@ -45,8 +45,6 @@
     </build>
 
     <properties>
-        <!-- util -->
-        <commons-lang3.version>3.5</commons-lang3.version>
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
         <avaitility.version>1.7.0</avaitility.version>

core-java-modules/core-java-concurrency-collections/pom.xml

@@ -62,7 +62,6 @@
     <properties>
         <!-- util -->
         <guava.version>21.0</guava.version>
-        <commons-lang3.version>3.5</commons-lang3.version>
         <commons-math3.version>3.6.1</commons-math3.version>
         <commons-collections4.version>4.1</commons-collections4.version>
         <collections-generic.version>4.01</collections-generic.version>

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

@@ -0,0 +1,3 @@
+## Relevant articles:
+
+- [Will an Error Be Caught by Catch Block in Java?](https://www.baeldung.com/java-error-catch)

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

@@ -14,15 +14,11 @@
 		<relativePath>../../parent-java</relativePath>
 	</parent>
 
-	<properties>
-		<commons-lang3.version>3.9</commons-lang3.version>
-	</properties>
-
 	<dependencies>
 		<dependency>
 			<groupId>junit</groupId>
 			<artifactId>junit</artifactId>
-			<version>4.12</version>
+			<version>${junit.version}</version>
 			<scope>test</scope>
 		</dependency>
 		<dependency>
@@ -32,4 +28,8 @@
 		</dependency>
 	</dependencies>
 
+	<properties>
+		<commons-lang3.version>3.9</commons-lang3.version>
+	</properties>
+
 </project>

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

@@ -248,7 +248,6 @@
     <properties>
 
         <!-- util -->
-        <commons-lang3.version>3.5</commons-lang3.version>
         <bouncycastle.version>1.55</bouncycastle.version>
         <commons-codec.version>1.10</commons-codec.version>
         <commons-math3.version>3.6.1</commons-math3.version>

core-java-modules/core-java-jpms/decoupling-pattern1/consumermodule/pom.xml

@@ -11,6 +11,14 @@
         <version>1.0</version>
     </parent>
     
+    <dependencies>
+        <dependency>
+            <groupId>com.baeldung.servicemodule</groupId>
+            <artifactId>servicemodule</artifactId>
+            <version>1.0</version>           
+        </dependency>
+    </dependencies>
+    
     <build>
         <plugins>
             <plugin>
@@ -19,12 +27,4 @@
             </plugin>
         </plugins>
     </build>
-    
-    <dependencies>
-        <dependency>
-            <groupId>com.baeldung.servicemodule</groupId>
-            <artifactId>servicemodule</artifactId>
-            <version>1.0</version>           
-        </dependency>
-    </dependencies>
 </project>

core-java-modules/core-java-jpms/decoupling-pattern2/consumermodule/pom.xml

@@ -2,17 +2,18 @@
 <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">
-    <parent>
-        <artifactId>com.baeldung.decoupling-pattern2</artifactId>
-        <groupId>decoupling-pattern2</groupId>
-        <version>1.0-SNAPSHOT</version>
-    </parent>
     <modelVersion>4.0.0</modelVersion>
 
     <groupId>com.baeldung.consumermodule</groupId>
     <artifactId>consumermodule</artifactId>
     <version>1.0</version>
 
+    <parent>
+        <artifactId>com.baeldung.decoupling-pattern2</artifactId>
+        <groupId>decoupling-pattern2</groupId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+
     <dependencies>
         <dependency>
             <groupId>com.baeldung.servicemodule</groupId>

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

@@ -35,7 +35,6 @@
     </dependencies>
 
     <properties>
-        <commons-lang3.version>3.5</commons-lang3.version>
         <assertj.version>3.6.1</assertj.version>
     </properties>
 </project>

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

@@ -0,0 +1,3 @@
+## Relevant articles:
+
+- [Why Do Local Variables Used in Lambdas Have to Be Final or Effectively Final?](https://www.baeldung.com/java-lambda-effectively-final-local-variables)

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

@@ -6,3 +6,4 @@
 - [Generic Constructors in Java](https://www.baeldung.com/java-generic-constructors)
 - [Cannot Reference “X” Before Supertype Constructor Has Been Called](https://www.baeldung.com/java-cannot-reference-x-before-supertype-constructor-error)
 - [Anonymous Classes in Java](https://www.baeldung.com/java-anonymous-classes)
+- [Raw Types in Java](https://www.baeldung.com/raw-types-java)

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

@@ -75,13 +75,7 @@
     </build>
 
     <properties>
-        
-        <!-- marshalling -->
-        <jackson.version>2.8.5</jackson.version>
         <gson.version>2.8.2</gson.version>
-
-        <!-- util -->
-        <commons-lang3.version>3.5</commons-lang3.version>
         <!-- testing -->
         <assertj-core.version>3.10.0</assertj-core.version>
         <equalsverifier.version>3.0.3</equalsverifier.version>

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

@@ -75,9 +75,6 @@
 
     <properties>
         <gson.version>2.8.2</gson.version>
-
-        <!-- util -->
-        <commons-lang3.version>3.5</commons-lang3.version>
         
         <javax.mail.version>1.5.0-b01</javax.mail.version>
         

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

@@ -42,8 +42,6 @@
 
     <properties>
         <javax.mail.version>1.5.0-b01</javax.mail.version>
-        <commons-io.version>2.5</commons-io.version>
-        <commons-lang3.version>3.5</commons-lang3.version>
         <springframework.spring-web.version>4.3.4.RELEASE</springframework.spring-web.version>
     </properties>	
 </project>

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

@@ -1,3 +1,3 @@
 ## Relevant articles:
 
-- [Determine File Creating Date in Java](https://www.baeldung.com/file-creation-date-java)
+- [Determine File Creating Date in Java](https://www.baeldung.com/java-file-creation-date)

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

@@ -8,9 +8,9 @@
     <packaging>jar</packaging>
 
     <parent>
-      <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung</groupId>
-      <artifactId>parent-java</artifactId>
+        <artifactId>parent-java</artifactId>
-      <version>0.0.1-SNAPSHOT</version>
+        <version>0.0.1-SNAPSHOT</version>
-      <relativePath>../../parent-java</relativePath>
+        <relativePath>../../parent-java</relativePath>
     </parent>
 </project>

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

@@ -2,4 +2,5 @@
 
 ## Core Java Optional
 
-### Relevant Articles: 
+### Relevant Articles: 
+- [Java Optional as Return Type](https://www.baeldung.com/java-optional-return)

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

@@ -1,22 +1,14 @@
 <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>
+    <modelVersion>4.0.0</modelVersion>
-  <parent>
+    <artifactId>core-java-optional</artifactId>
-    <groupId>com.baeldung.core-java-modules</groupId>
+    <version>0.1.0-SNAPSHOT</version>
-    <artifactId>core-java-modules</artifactId>
+    <packaging>jar</packaging>
-    <version>1.0.0-SNAPSHOT</version>
+	
-  </parent>
+    <parent>
-  <artifactId>core-java-optional</artifactId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-  <version>0.1.0-SNAPSHOT</version>
+        <artifactId>core-java-modules</artifactId>
-  <packaging>jar</packaging>
+        <version>1.0.0-SNAPSHOT</version>
-
+    </parent>
-    <properties>
-        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <maven.compiler.source>1.8</maven.compiler.source>
-        <maven.compiler.target>1.8</maven.compiler.target>
-        <hibernate.core.version>5.4.0.Final</hibernate.core.version>
-        <h2database.version>1.4.197</h2database.version>
-        <jackson.databind.version>2.9.8</jackson.databind.version>
-    </properties>
   
     <dependencies>
         <dependency>
@@ -27,12 +19,12 @@
         <dependency>
             <groupId>com.h2database</groupId>
             <artifactId>h2</artifactId>
-            <version>${h2database.version}</version>
+            <version>${h2.version}</version>
         </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
-            <version>${jackson.databind.version}</version>
+            <version>${jackson.version}</version>
         </dependency>
     </dependencies>
 
@@ -50,4 +42,11 @@
         </plugins>
 
     </build>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+        <hibernate.core.version>5.4.0.Final</hibernate.core.version>
+    </properties>
 </project>

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

@@ -68,7 +68,6 @@
 
     <properties>
         <!-- util -->
-        <commons-lang3.version>3.5</commons-lang3.version>
         <commons-collections4.version>4.1</commons-collections4.version>
         <collections-generic.version>4.01</collections-generic.version>
     

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

@@ -23,11 +23,4 @@
        
     </dependencies>
 
-    <properties>
-
-        <!-- util -->
-        <commons-lang3.version>3.8.1</commons-lang3.version>
-      
-    </properties>
-
 </project>

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

@@ -43,7 +43,6 @@
     <properties>
 
         <!-- util -->
-        <commons-lang3.version>3.8.1</commons-lang3.version>
         <bouncycastle.version>1.60</bouncycastle.version>
         <commons-codec.version>1.11</commons-codec.version>
 

core-java-modules/core-java-security/src/main/java/com/baeldung/random/SecureRandomDemo.java

@@ -0,0 +1,36 @@
+package com.baeldung.random;
+
+import java.security.SecureRandom;
+import java.security.NoSuchAlgorithmException;
+import java.util.stream.IntStream;
+import java.util.stream.LongStream;
+import java.util.stream.DoubleStream;
+
+public interface SecureRandomDemo {
+
+    public static void generateSecureRandomValues() {
+        SecureRandom sr = new SecureRandom();
+
+        int randomInt = sr.nextInt();
+        long randomLong = sr.nextLong();
+        float randomFloat = sr.nextFloat();
+        double randomDouble = sr.nextDouble();
+        boolean randomBoolean = sr.nextBoolean();
+
+        IntStream randomIntStream = sr.ints();
+        LongStream randomLongStream = sr.longs();
+        DoubleStream randomDoubleStream = sr.doubles();
+
+        byte[] values = new byte[124];
+        sr.nextBytes(values);
+    }
+
+    public static SecureRandom getSecureRandomForAlgorithm(String algorithm) throws NoSuchAlgorithmException {
+        if (algorithm == null || algorithm.isEmpty()) {
+            return new SecureRandom();
+        }
+
+        return SecureRandom.getInstance(algorithm);
+    }
+
+}

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

@@ -264,7 +264,6 @@
 
         <!-- util -->
         <guava.version>23.0</guava.version>
-        <commons-lang3.version>3.5</commons-lang3.version>
         <bouncycastle.version>1.55</bouncycastle.version>
         <commons-codec.version>1.10</commons-codec.version>
         <commons-math3.version>3.6.1</commons-math3.version>

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

@@ -13,7 +13,6 @@
         <relativePath>../../parent-java</relativePath>
     </parent>
 
-
     <dependencies>
         <dependency>
             <groupId>commons-io</groupId>
@@ -114,7 +113,7 @@
         <dependency>
             <groupId>com.h2database</groupId>
             <artifactId>h2</artifactId>
-            <version>${h2database.version}</version>
+            <version>${h2.version}</version>
         </dependency>
         <!-- instrumentation -->
         <dependency>
@@ -454,8 +453,6 @@
         <gson.version>2.8.2</gson.version>
 
         <!-- util -->
-        <commons-lang3.version>3.9</commons-lang3.version>
-        <commons-io.version>2.5</commons-io.version>
         <commons-math3.version>3.6.1</commons-math3.version>
         <decimal4j.version>1.0.3</decimal4j.version>
         <unix4j.version>0.4</unix4j.version>
@@ -472,7 +469,6 @@
         <maven-surefire-plugin.version>2.21.0</maven-surefire-plugin.version>
         
         <javamoney.moneta.version>1.1</javamoney.moneta.version>
-        <h2database.version>1.4.197</h2database.version>
         <esapi.version>2.1.0.1</esapi.version>
         <jmh-core.version>1.19</jmh-core.version>
        

core-java-modules/multimodulemavenproject/daomodule/pom.xml

@@ -1,15 +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>
+    <groupId>com.baeldung.daomodule</groupId>
+    <artifactId>daomodule</artifactId>
+    <version>1.0</version>
+    <packaging>jar</packaging>
+    
     <parent>
         <groupId>com.baeldung.multimodulemavenproject</groupId>
         <artifactId>multimodulemavenproject</artifactId>
         <version>1.0</version>
     </parent>
-    <groupId>com.baeldung.daomodule</groupId>
-    <artifactId>daomodule</artifactId>
-    <version>1.0</version>
-    <packaging>jar</packaging>
     
     <build>
         <plugins>

core-java-modules/multimodulemavenproject/entitymodule/pom.xml

@@ -1,15 +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>
+    <groupId>com.baeldung.entitymodule</groupId>
+    <artifactId>entitymodule</artifactId>
+    <version>1.0</version>
+    <packaging>jar</packaging>
+
     <parent>
         <groupId>com.baeldung.multimodulemavenproject</groupId>
         <artifactId>multimodulemavenproject</artifactId>
         <version>1.0</version>
     </parent>
-    <groupId>com.baeldung.entitymodule</groupId>
-    <artifactId>entitymodule</artifactId>
-    <version>1.0</version>
-    <packaging>jar</packaging>
     
     <build>
         <plugins>

core-java-modules/multimodulemavenproject/mainappmodule/pom.xml

@@ -1,15 +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>
+    <groupId>com.baeldung.mainappmodule</groupId>
+    <artifactId>mainappmodule</artifactId>
+    <version>1.0</version>
+    <packaging>jar</packaging>
+
     <parent>
         <groupId>com.baeldung.multimodulemavenproject</groupId>
         <artifactId>multimodulemavenproject</artifactId>
         <version>1.0</version>
     </parent>
-    <groupId>com.baeldung.mainappmodule</groupId>
-    <artifactId>mainappmodule</artifactId>
-    <version>1.0</version>
-    <packaging>jar</packaging>
     
     <dependencies>
         <dependency>

core-java-modules/multimodulemavenproject/pom.xml

@@ -14,18 +14,25 @@
         <relativePath>../../</relativePath>
     </parent>
     
+    <modules>
+        <module>entitymodule</module>
+        <module>daomodule</module>
+        <module>userdaomodule</module>
+        <module>mainappmodule</module>
+    </modules>
+    
     <dependencyManagement>
         <dependencies>
             <dependency>
                 <groupId>junit</groupId>
                 <artifactId>junit</artifactId>
-                <version>4.12</version>
+                <version>${junit.version}</version>
                 <scope>test</scope>
             </dependency>
             <dependency>
                 <groupId>org.assertj</groupId>
                 <artifactId>assertj-core</artifactId>
-                <version>3.12.2</version>
+                <version>${assertj-core.version}</version>
                 <scope>test</scope>
             </dependency>
         </dependencies>
@@ -49,14 +56,8 @@
         </pluginManagement>
     </build>
     
-    <modules>
-        <module>entitymodule</module>
-        <module>daomodule</module>
-        <module>userdaomodule</module>
-        <module>mainappmodule</module>
-    </modules>
-    
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <assertj-core.version>3.12.2</assertj-core.version>
     </properties>
 </project>

core-java-modules/multimodulemavenproject/userdaomodule/pom.xml

@@ -1,24 +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>
+    <groupId>com.baeldung.userdaomodule</groupId>
+    <artifactId>userdaomodule</artifactId>
+    <version>1.0</version>
+    <packaging>jar</packaging>
+
     <parent>
         <groupId>com.baeldung.multimodulemavenproject</groupId>
         <artifactId>multimodulemavenproject</artifactId>
         <version>1.0</version>
     </parent>
-    <groupId>com.baeldung.userdaomodule</groupId>
-    <artifactId>userdaomodule</artifactId>
-    <version>1.0</version>
-    <packaging>jar</packaging>
-    
-    <build>
-        <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-compiler-plugin</artifactId>
-            </plugin>
-        </plugins>
-    </build>
     
     <dependencies>
         <dependency>
@@ -33,6 +25,15 @@
         </dependency>
     </dependencies>
     
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+    
     <properties>
         <maven.compiler.source>9</maven.compiler.source>
         <maven.compiler.target>9</maven.compiler.target>

core-java-modules/pre-jpms/pom.xml

@@ -18,9 +18,10 @@
 		<dependency>
 			<groupId>org.slf4j</groupId>
 			<artifactId>slf4j-api</artifactId>
-			<version>1.7.25</version>
+			<version>${org.slf4j.version}</version>
 		</dependency>
 	</dependencies>
+
 	<build>
 		<finalName>pre-jpms</finalName>
 		<plugins>
@@ -65,9 +66,9 @@
 					</archive>
 				</configuration>
 			</plugin>
-
 		</plugins>
 	</build>
+
 	<properties>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 	</properties>

core-kotlin-io/pom.xml

@@ -22,7 +22,7 @@
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter</artifactId>
-            <version>${junit.jupiter.version}</version>
+            <version>${junit-jupiter.version}</version>
             <scope>test</scope>
         </dependency>
         <dependency>
@@ -88,7 +88,7 @@
 
     <properties>
         <kotlin.version>1.3.30</kotlin.version>
-        <junit.jupiter.version>5.4.2</junit.jupiter.version>
+        <junit-jupiter.version>5.4.2</junit-jupiter.version>
         <mockito.version>2.27.0</mockito.version>
         <byte-buddy.version>1.9.12</byte-buddy.version>
         <assertj.version>3.10.0</assertj.version>

core-kotlin/pom.xml

@@ -39,7 +39,7 @@
         <dependency>
             <groupId>com.h2database</groupId>
             <artifactId>h2</artifactId>
-            <version>${h2database.version}</version>
+            <version>${h2.version}</version>
         </dependency>
         <dependency>
             <groupId>com.github.kittinunf.fuel</groupId>
@@ -76,11 +76,9 @@
 
     <properties>
         <commons-math3.version>3.6.1</commons-math3.version>
-        <commons-lang3.version>3.8.1</commons-lang3.version>
         <junit.platform.version>1.1.1</junit.platform.version>
         <junit.vintage.version>5.2.0</junit.vintage.version>
         <assertj.version>3.10.0</assertj.version>
-        <h2database.version>1.4.197</h2database.version>
         <fuel.version>1.15.0</fuel.version>
 		<kovenant.version>3.3.0</kovenant.version>
 		<injekt-core.version>1.16.1</injekt-core.version>

couchbase/pom.xml

@@ -69,7 +69,6 @@
     <properties>
         <couchbase.client.version>2.5.0</couchbase.client.version>
         <spring-framework.version>4.3.5.RELEASE</spring-framework.version>
-        <commons-lang3.version>3.5</commons-lang3.version>
     </properties>
 
 </project>

custom-pmd/pom.xml

@@ -7,6 +7,12 @@
     <name>custom-pmd</name>
     <packaging>jar</packaging>
     <url>http://maven.apache.org</url>
+    
+    <parent>
+        <artifactId>parent-modules</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
 
     <dependencies>
         <dependency>

disruptor/pom.xml

@@ -115,7 +115,6 @@
 
     <properties>
         <!-- util -->
-        <commons-lang3.version>3.5</commons-lang3.version>
         <disruptor.version>3.3.6</disruptor.version>
         <!-- testing -->
         <testng.version>6.10</testng.version>

dozer/pom.xml

@@ -26,7 +26,6 @@
     </dependencies>
 
     <properties>
-        <commons-lang3.version>3.5</commons-lang3.version>
         <dozer.version>5.5.1</dozer.version>
     </properties>
 

flyway-cdi-extension/pom.xml

@@ -8,6 +8,13 @@
     <version>1.0-SNAPSHOT</version>
     <name>flyway-cdi-extension</name>
 
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>..</relativePath>
+    </parent>
+
     <dependencies>
         <dependency>
             <groupId>javax.enterprise</groupId>
@@ -51,6 +58,5 @@
 		<flyway-core.version>5.1.4</flyway-core.version>
 		<tomcat-jdbc.version>8.5.33</tomcat-jdbc.version>
 		<javax.annotation-api.version>1.3.2</javax.annotation-api.version>
-		<h2.version>1.4.197</h2.version>
     </properties>
 </project>

gson/pom.xml

@@ -64,7 +64,6 @@
         <!-- marshalling -->
         <gson.version>2.8.0</gson.version>
         <!-- util -->
-        <commons-lang3.version>3.5</commons-lang3.version>
         <commons-collections4.version>4.1</commons-collections4.version>
         <joda-time.version>2.9.6</joda-time.version>
     </properties>

guava-collections/pom.xml

@@ -55,7 +55,6 @@
     <properties>
         <!-- util -->
         <guava.version>24.0-jre</guava.version>
-        <commons-lang3.version>3.5</commons-lang3.version>
         <commons-collections4.version>4.1</commons-collections4.version>
 
         <!-- testing -->

guava/pom.xml

@@ -49,7 +49,6 @@
     <properties>
         <!-- util -->
         <guava.version>24.0-jre</guava.version>
-        <commons-lang3.version>3.5</commons-lang3.version>
 
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>

httpclient-simple/pom.xml

@@ -297,7 +297,6 @@
     <properties>
         <!-- util -->
         <guava.version>19.0</guava.version>
-        <commons-lang3.version>3.5</commons-lang3.version>
         <commons-codec.version>1.10</commons-codec.version>
         <httpasyncclient.version>4.1.4</httpasyncclient.version>
         <!-- testing -->
@@ -305,7 +304,6 @@
         <httpcore.version>4.4.11</httpcore.version>
         <httpclient.version>4.5.8</httpclient.version> <!-- 4.3.6 --> <!-- 4.4-beta1 -->
         <!-- maven plugins -->
-        <maven-war-plugin.version>2.6</maven-war-plugin.version>
         <cargo-maven2-plugin.version>1.6.1</cargo-maven2-plugin.version>
     </properties>
 

httpclient/pom.xml

@@ -120,7 +120,6 @@
     <properties>
         <!-- util -->
         <guava.version>19.0</guava.version>
-        <commons-lang3.version>3.5</commons-lang3.version>
         <commons-codec.version>1.10</commons-codec.version>
         <httpasyncclient.version>4.1.4</httpasyncclient.version>
         <!-- testing -->

hystrix/pom.xml

@@ -65,7 +65,6 @@
         <hystrix-core.version>1.5.8</hystrix-core.version>
         <rxjava-core.version>0.20.7</rxjava-core.version>
         <!-- maven plugins -->
-        <maven-war-plugin.version>2.6</maven-war-plugin.version>
         <maven-resources-plugin.version>2.7</maven-resources-plugin.version>
         <hystrix-metrics-event-stream.version>1.5.8</hystrix-metrics-event-stream.version>
         <hystrix-dashboard.version>1.5.8</hystrix-dashboard.version>

jackson-2/README.md

@@ -9,4 +9,4 @@ The "REST With Spring" Classes: http://bit.ly/restwithspring
 - [Mapping Multiple JSON Fields to a Single Java Field](https://www.baeldung.com/json-multiple-fields-single-java-field)
 - [How to Process YAML with Jackson](https://www.baeldung.com/jackson-yaml)
 - [Working with Tree Model Nodes in Jackson](https://www.baeldung.com/jackson-json-node-tree-model)
-
+- [Converting JSON to CSV in Java](https://www.baeldung.com/java-converting-json-to-csv)

jackson-2/pom.xml

@@ -26,21 +26,21 @@
         <dependency>
             <groupId>com.fasterxml.jackson.dataformat</groupId>
             <artifactId>jackson-dataformat-yaml</artifactId>
-            <version>2.9.8</version>
+            <version>${jackson.version}</version>
         </dependency>
         
         <!-- CSV -->
         <dependency>
             <groupId>com.fasterxml.jackson.dataformat</groupId>
             <artifactId>jackson-dataformat-csv</artifactId>
-            <version>2.9.8</version>
+            <version>${jackson.version}</version>
         </dependency>        
 
         <!-- Allow use of LocalDate -->
         <dependency>
             <groupId>com.fasterxml.jackson.datatype</groupId>
             <artifactId>jackson-datatype-jsr310</artifactId>
-            <version>2.9.8</version>
+            <version>${jackson.version}</version>
         </dependency>
 
 

jackson-2/src/test/java/com/baeldung/jackson/json/compare/JsonCompareUnitTest.java

@@ -0,0 +1,126 @@
+package com.baeldung.jackson.json.compare;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.util.Comparator;
+
+import org.junit.Test;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.NumericNode;
+import com.fasterxml.jackson.databind.node.TextNode;
+
+public class JsonCompareUnitTest {
+
+    @Test
+    public void givenTwoSameJsonDataObjects_whenCompared_thenAreEqual() throws IOException {
+        ObjectMapper mapper = new ObjectMapper();
+
+        String s1 = "{\"employee\": {\"id\": \"1212\",\"fullName\": \"John Miles\", \"age\": 34 }}";
+        String s2 = "{\"employee\": {\"id\": \"1212\",\"age\": 34, \"fullName\": \"John Miles\" }}";
+
+        JsonNode actualObj1 = mapper.readTree(s1);
+        JsonNode actualObj2 = mapper.readTree(s2);
+
+        assertEquals(actualObj1, actualObj2);
+
+    }
+
+    @Test
+    public void givenTwoSameNestedJsonDataObjects_whenCompared_thenEqual() throws IOException {
+        ObjectMapper mapper = new ObjectMapper();
+
+        String s1 = "{\"employee\": {\"id\": \"1212\",\"fullName\": \"John Miles\",\"age\": 34, \"contact\":{\"email\": \"john@xyz.com\",\"phone\": \"9999999999\"} }}";
+        String s2 = "{\"employee\": {\"id\": \"1212\",\"fullName\": \"John Miles\",\"age\": 34, \"contact\":{\"email\": \"john@xyz.com\",\"phone\": \"9999999999\"} }}";
+
+        JsonNode actualObj1 = mapper.readTree(s1);
+        JsonNode actualObj2 = mapper.readTree(s2);
+
+        assertEquals(actualObj1, actualObj2);
+
+    }
+
+    @Test
+    public void givenTwoSameListJsonDataObjects_whenCompared_thenEqual() throws IOException {
+        ObjectMapper mapper = new ObjectMapper();
+
+        String s1 = "{\"employee\": {\"id\": \"1212\",\"fullName\": \"John Miles\",\"age\": 34, \"skills\":[\"Java\", \"C++\", \"Python\"] }}";
+        String s2 = "{\"employee\": {\"id\": \"1212\",\"fullName\": \"John Miles\",\"age\": 34, \"skills\":[\"Java\", \"C++\", \"Python\"] }}";
+
+        JsonNode actualObj1 = mapper.readTree(s1);
+        JsonNode actualObj2 = mapper.readTree(s2);
+
+        assertEquals(actualObj1, actualObj2);
+
+    }
+
+    @Test
+    public void givenTwoJsonDataObjects_whenComparedUsingCustomNumericNodeComparator_thenEqual() throws IOException {
+        ObjectMapper mapper = new ObjectMapper();
+
+        String s1 = "{\"name\": \"John\",\"score\":5.0}";
+        String s2 = "{\"name\": \"John\",\"score\":5}";
+        JsonNode actualObj1 = mapper.readTree(s1);
+        JsonNode actualObj2 = mapper.readTree(s2);
+
+        NumericNodeComparator cmp = new NumericNodeComparator();
+
+        assertNotEquals(actualObj1, actualObj2);
+        assertTrue(actualObj1.equals(cmp, actualObj2));
+
+    }
+    
+    public class NumericNodeComparator implements Comparator<JsonNode> {
+        @Override
+        public int compare(JsonNode o1, JsonNode o2) {
+            if (o1.equals(o2)) {
+                return 0;
+            }
+            if ((o1 instanceof NumericNode) && (o2 instanceof NumericNode)) {
+                Double d1 = ((NumericNode) o1).asDouble();
+                Double d2 = ((NumericNode) o2).asDouble();
+                if (d1.compareTo(d2) == 0) {
+                    return 0;
+                }
+            }
+            return 1;
+        }
+    }
+    
+    @Test
+    public void givenTwoJsonDataObjects_whenComparedUsingCustomTextNodeComparator_thenEqual() throws IOException {
+        ObjectMapper mapper = new ObjectMapper();
+
+        String s1 = "{\"name\": \"JOHN\",\"score\":5}";
+        String s2 = "{\"name\": \"John\",\"score\":5}";
+        JsonNode actualObj1 = mapper.readTree(s1);
+        JsonNode actualObj2 = mapper.readTree(s2);
+
+        TextNodeComparator cmp = new TextNodeComparator();
+
+        assertNotEquals(actualObj1, actualObj2);
+        assertTrue(actualObj1.equals(cmp, actualObj2));
+
+    }
+    
+    public class TextNodeComparator implements Comparator<JsonNode> {
+        @Override
+        public int compare(JsonNode o1, JsonNode o2) {
+            if (o1.equals(o2)) {
+                return 0;
+            }
+            if ((o1 instanceof TextNode) && (o2 instanceof TextNode)) {
+                String s1 = ((TextNode) o1).asText();
+                String s2 = ((TextNode) o2).asText();
+                if (s1.equalsIgnoreCase(s2)) {
+                    return 0;
+                }
+            }
+            return 1;
+        }
+    }
+}

jackson-simple/pom.xml

@@ -118,7 +118,6 @@
 
     <properties>
         <!-- util -->
-        <commons-lang3.version>3.8</commons-lang3.version>
         <joda-time.version>2.10</joda-time.version>
         <gson.version>2.8.5</gson.version>
         <commons-collections4.version>4.2</commons-collections4.version>

jackson/pom.xml

@@ -118,7 +118,6 @@
 
     <properties>
         <!-- util -->
-        <commons-lang3.version>3.8</commons-lang3.version>
         <joda-time.version>2.10</joda-time.version>
         <gson.version>2.8.5</gson.version>
         <commons-collections4.version>4.2</commons-collections4.version>

java-collections-conversions/README.md

@@ -10,4 +10,7 @@
 - [Converting a List to String in Java](http://www.baeldung.com/java-list-to-string)
 - [How to Convert List to Map in Java](http://www.baeldung.com/java-list-to-map)
 - [Array to String Conversions](https://www.baeldung.com/java-array-to-string)
-- [Converting a Collection to ArrayList in Java](https://www.baeldung.com/java-convert-collection-arraylist)
+- [Converting a Collection to ArrayList in Java](https://www.baeldung.com/java-convert-collection-arraylist)
+- [Java 8 Collectors toMap](https://www.baeldung.com/java-collectors-tomap)
+- [Converting Iterable to Collection in Java](https://www.baeldung.com/java-iterable-to-collection)
+- [Converting Iterator to List](https://www.baeldung.com/java-convert-iterator-to-list)

java-collections-conversions/pom.xml

@@ -33,7 +33,6 @@
     </dependencies>
 
     <properties>
-        <commons-lang3.version>3.5</commons-lang3.version>
         <commons-collections4.version>4.1</commons-collections4.version>
         <assertj.version>3.6.1</assertj.version>
     </properties>

java-collections-conversions/src/test/java/com/baeldung/java/collections/IterableToCollectionUnitTest.java

@@ -1,4 +1,4 @@
-package org.baeldung.java.collections;
+package com.baeldung.java.collections;
 
 import static org.hamcrest.Matchers.contains;
 import static org.junit.Assert.assertThat;

java-collections-maps-2/pom.xml

@@ -54,7 +54,6 @@
         <trove4j.version>3.0.2</trove4j.version>
         <fastutil.version>8.1.0</fastutil.version>
         <colt.version>1.2.0</colt.version>
-        <commons-lang3.version>3.8.1</commons-lang3.version>
         <assertj.version>3.11.1</assertj.version>
     </properties>
 

java-collections-maps/pom.xml

@@ -44,7 +44,6 @@
     </dependencies>
 
     <properties>
-        <commons-lang3.version>3.5</commons-lang3.version>
         <commons-collections4.version>4.1</commons-collections4.version>
         <collections-generic.version>4.01</collections-generic.version>
         <avaitility.version>1.7.0</avaitility.version>

java-dates-2/pom.xml

@@ -25,7 +25,7 @@
         <dependency>
             <groupId>commons-validator</groupId>
             <artifactId>commons-validator</artifactId>
-            <version>1.6</version>
+            <version>${commons-validator.version}</version>
         </dependency>
 
         <!-- test scoped -->
@@ -63,6 +63,7 @@
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
         <joda-time.version>2.10</joda-time.version>
+        <commons-validator.version>1.6</commons-validator.version>
         <maven.compiler.source>1.9</maven.compiler.source>
         <maven.compiler.target>1.9</maven.compiler.target>
     </properties>

java-dates/pom.xml

@@ -74,8 +74,6 @@
     </build>
 
     <properties>
-        <!-- util -->
-        <commons-lang3.version>3.5</commons-lang3.version>
         <joda-time.version>2.10</joda-time.version>
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>

java-ee-8-security-api/pom.xml

@@ -72,8 +72,6 @@
         <javaee-version>8.0</javaee-version>
         <liberty-maven-plugin.version>2.3</liberty-maven-plugin.version>
         <openliberty-runtime.version>18.0.0.1</openliberty-runtime.version>
-        
-        <maven-war-plugin.version>3.2.2</maven-war-plugin.version>
     </properties>
 
 </project>

java-math/pom.xml

@@ -42,7 +42,7 @@
         <dependency>
             <groupId>com.github.dpaukov</groupId>
             <artifactId>combinatoricslib3</artifactId>
-            <version>3.3.0</version>
+            <version>${combinatoricslib3.version}</version>
          </dependency>
     </dependencies>
 
@@ -63,6 +63,7 @@
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
         <commons-codec.version>1.11</commons-codec.version>
         <guava.version>27.0.1-jre</guava.version>
+        <combinatoricslib3.version>3.3.0</combinatoricslib3.version>
     </properties>
 
 </project>

java-numbers-2/.gitignore

@@ -0,0 +1,26 @@
+*.class
+
+0.*
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+.resourceCache
+
+# Packaged files #
+*.jar
+*.war
+*.ear
+
+# Files generated by integration tests
+*.txt
+backup-pom.xml
+/bin/
+/temp
+
+#IntelliJ specific
+.idea/
+*.iml