Merge branch 'master' into core-java-move-2

.gitignore

@@ -30,7 +30,7 @@ out/
 .DS_Store
 
 # Maven
-log/
+log/*
 target/
 
 # Gradle
@@ -84,3 +84,4 @@ software-security/sql-injection-samples/derby.log
 spring-soap/src/main/java/com/baeldung/springsoap/gen/
 /report-*.json
 transaction.log
+*-shell.log

akka-http/README.md

@@ -1,3 +1,7 @@
-## Relevant articles:
+## Akka HTTP
+
+This module contains articles about Akka HTTP. 
+
+### Relevant articles:
 
 - [Introduction to Akka HTTP](https://www.baeldung.com/akka-http)

akka-streams/README.md

@@ -1,3 +1,7 @@
+## Akka Streams
+
+This module contains articles about Akka Streams. 
+
 ### Relevant articles
 
 - [Guide to Akka Streams](https://www.baeldung.com/akka-streams)

algorithms-genetic/README.md

@@ -1,4 +1,8 @@
-## Relevant articles:
+## Genetic Algorithms
+
+This module contains articles about genetic algorithms. 
+
+### Relevant articles:
 
 - [Introduction to Jenetics Library](https://www.baeldung.com/jenetics)
 - [Ant Colony Optimization](https://www.baeldung.com/java-ant-colony-optimization)

algorithms-miscellaneous-1/README.md

@@ -1,4 +1,9 @@
-## Relevant articles:
+## Algorithms - Miscellaneous
+
+This module contains articles about algorithms. Some classes of algorithms, e.g., [sorting](/../algorithms-sorting) and
+[genetic algorithms](/../algorithms-genetic), have their own dedicated modules. 
+
+### Relevant articles:
 
 - [Validating Input With Finite Automata in Java](https://www.baeldung.com/java-finite-automata)
 - [Example of Hill Climbing Algorithm](https://www.baeldung.com/java-hill-climbing-algorithm)
@@ -7,3 +12,4 @@
 - [Introduction to Minimax Algorithm](https://www.baeldung.com/java-minimax-algorithm)
 - [How to Calculate Levenshtein Distance in Java?](https://www.baeldung.com/java-levenshtein-distance)
 - [How to Find the Kth Largest Element in Java](https://www.baeldung.com/java-kth-largest-element)
+- More articles: [[next -->]](/../algorithms-miscellaneous-2)

algorithms-miscellaneous-2/README.md

@@ -1,4 +1,9 @@
-## Relevant articles:
+## Algorithms - Miscellaneous
+
+This module contains articles about algorithms. Some classes of algorithms, e.g., [sorting](/../algorithms-sorting) and
+[genetic algorithms](/../algorithms-genetic), have their own dedicated modules. 
+
+### Relevant articles:
 
 - [Dijkstra Shortest Path Algorithm in Java](https://www.baeldung.com/java-dijkstra)
 - [Introduction to Cobertura](https://www.baeldung.com/cobertura)
@@ -8,3 +13,4 @@
 - [Create a Sudoku Solver in Java](https://www.baeldung.com/java-sudoku)
 - [Displaying Money Amounts in Words](https://www.baeldung.com/java-money-into-words)
 - [A Collaborative Filtering Recommendation System in Java](https://www.baeldung.com/java-collaborative-filtering-recommendations)
+- More articles: [[<-- prev]](/../algorithms-miscellaneous-1) [[next -->]](/../algorithms-miscellaneous-3)

algorithms-miscellaneous-3/README.md

@@ -14,4 +14,6 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [A Guide to the Folding Technique in Java](https://www.baeldung.com/folding-hashing-technique)
 - [Creating a Triangle with for Loops in Java](https://www.baeldung.com/java-print-triangle)
 - [Efficient Word Frequency Calculator in Java](https://www.baeldung.com/java-word-frequency)
+- [Interpolation Search in Java](https://www.baeldung.com/java-interpolation-search)
+- [The K-Means Clustering Algorithm in Java](https://www.baeldung.com/java-k-means-clustering-algorithm)
 - More articles: [[<-- prev]](/algorithms-miscellaneous-2) [[next -->]](/algorithms-miscellaneous-4)

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/breadthfirstsearch/BreadthFirstSearchAlgorithm.java

@@ -0,0 +1,54 @@
+package com.baeldung.algorithms.breadthfirstsearch;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.*;
+
+public class BreadthFirstSearchAlgorithm {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(BreadthFirstSearchAlgorithm.class);
+
+    public static <T> Optional<Tree<T>> search(T value, Tree<T> root) {
+        Queue<Tree<T>> queue = new ArrayDeque<>();
+        queue.add(root);
+
+        Tree<T> currentNode;
+        while (!queue.isEmpty()) {
+            currentNode = queue.remove();
+            LOGGER.info("Visited node with value: {}", currentNode.getValue());
+
+            if (currentNode.getValue().equals(value)) {
+                return Optional.of(currentNode);
+            } else {
+                queue.addAll(currentNode.getChildren());
+            }
+        }
+
+        return Optional.empty();
+    }
+
+    public static <T> Optional<Node<T>> search(T value, Node<T> start) {
+        Queue<Node<T>> queue = new ArrayDeque<>();
+        queue.add(start);
+
+        Node<T> currentNode;
+        Set<Node<T>> alreadyVisited = new HashSet<>();
+
+        while (!queue.isEmpty()) {
+            currentNode = queue.remove();
+            LOGGER.info("Visited node with value: {}", currentNode.getValue());
+
+            if (currentNode.getValue().equals(value)) {
+                return Optional.of(currentNode);
+            } else {
+                alreadyVisited.add(currentNode);
+                queue.addAll(currentNode.getNeighbors());
+                queue.removeAll(alreadyVisited);
+            }
+        }
+
+        return Optional.empty();
+    }
+
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/breadthfirstsearch/Node.java

@@ -0,0 +1,31 @@
+package com.baeldung.algorithms.breadthfirstsearch;
+
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+
+public class Node<T> {
+
+    private T value;
+    private Set<Node<T>> neighbors;
+
+    public Node(T value) {
+        this.value = value;
+        this.neighbors = new HashSet<>();
+    }
+
+    public T getValue() {
+        return value;
+    }
+
+    public Set<Node<T>> getNeighbors() {
+        return Collections.unmodifiableSet(neighbors);
+    }
+
+    public void connect(Node<T> node) {
+        if (this == node) throw new IllegalArgumentException("Can't connect node to itself");
+        this.neighbors.add(node);
+        node.neighbors.add(this);
+    }
+
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/breadthfirstsearch/Tree.java

@@ -0,0 +1,34 @@
+package com.baeldung.algorithms.breadthfirstsearch;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class Tree<T> {
+
+    private T value;
+    private List<Tree<T>> children;
+
+    private Tree(T value) {
+        this.value = value;
+        this.children = new ArrayList<>();
+    }
+
+    public static <T> Tree<T> of(T value) {
+        return new Tree<>(value);
+    }
+
+    public T getValue() {
+        return value;
+    }
+
+    public List<Tree<T>> getChildren() {
+        return Collections.unmodifiableList(children);
+    }
+
+    public Tree<T> addChild(T value) {
+        Tree<T> newChild = new Tree<>(value);
+        children.add(newChild);
+        return newChild;
+    }
+}

algorithms-miscellaneous-3/src/test/java/com/baeldung/algorithms/breadthfirstsearch/BreadthFirstSearchAlgorithmUnitTest.java

@@ -0,0 +1,86 @@
+package com.baeldung.algorithms.breadthfirstsearch;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class BreadthFirstSearchAlgorithmUnitTest {
+
+    private Tree<Integer> root;
+    private Tree<Integer> rootFirstChild;
+    private Tree<Integer> depthMostChild;
+    private Tree<Integer> rootSecondChild;
+
+    private Node<Integer> start;
+    private Node<Integer> firstNeighbor;
+    private Node<Integer> firstNeighborNeighbor;
+    private Node<Integer> secondNeighbor;
+
+    @Test
+    void givenTree_whenSearchTen_thenRoot() {
+        initTree();
+        assertThat(BreadthFirstSearchAlgorithm.search(10, root)).isPresent().contains(root);
+    }
+
+    @Test
+    void givenTree_whenSearchThree_thenDepthMostValue() {
+        initTree();
+        assertThat(BreadthFirstSearchAlgorithm.search(3, root)).isPresent().contains(depthMostChild);
+    }
+
+    @Test
+    void givenTree_whenSearchFour_thenRootSecondChild() {
+        initTree();
+        assertThat(BreadthFirstSearchAlgorithm.search(4, root)).isPresent().contains(rootSecondChild);
+    }
+
+    @Test
+    void givenTree_whenSearchFive_thenNotFound() {
+        initTree();
+        assertThat(BreadthFirstSearchAlgorithm.search(5, root)).isEmpty();
+    }
+
+    private void initTree() {
+        root = Tree.of(10);
+        rootFirstChild = root.addChild(2);
+        depthMostChild = rootFirstChild.addChild(3);
+        rootSecondChild = root.addChild(4);
+    }
+
+    @Test
+    void givenNode_whenSearchTen_thenStart() {
+        initNode();
+        assertThat(BreadthFirstSearchAlgorithm.search(10, firstNeighborNeighbor)).isPresent().contains(start);
+    }
+
+    @Test
+    void givenNode_whenSearchThree_thenNeighborNeighbor() {
+        initNode();
+        assertThat(BreadthFirstSearchAlgorithm.search(3, firstNeighborNeighbor)).isPresent().contains(firstNeighborNeighbor);
+    }
+
+    @Test
+    void givenNode_whenSearchFour_thenSecondNeighbor() {
+        initNode();
+        assertThat(BreadthFirstSearchAlgorithm.search(4, firstNeighborNeighbor)).isPresent().contains(secondNeighbor);
+    }
+
+    @Test
+    void givenNode_whenSearchFive_thenNotFound() {
+        initNode();
+        assertThat(BreadthFirstSearchAlgorithm.search(5, firstNeighborNeighbor)).isEmpty();
+    }
+
+    private void initNode() {
+        start = new Node<>(10);
+        firstNeighbor = new Node<>(2);
+        start.connect(firstNeighbor);
+
+        firstNeighborNeighbor = new Node<>(3);
+        firstNeighbor.connect(firstNeighborNeighbor);
+        firstNeighborNeighbor.connect(start);
+
+        secondNeighbor = new Node<>(4);
+        start.connect(secondNeighbor);
+    }
+}

algorithms-miscellaneous-4/README.md

@@ -1,4 +1,9 @@
-## Relevant articles:
+## Algorithms - Miscellaneous
+
+This module contains articles about algorithms. Some classes of algorithms, e.g., [sorting](/../algorithms-sorting) and
+[genetic algorithms](/../algorithms-genetic), have their own dedicated modules. 
+
+### Relevant articles:
 
 - [Multi-Swarm Optimization Algorithm in Java](https://www.baeldung.com/java-multi-swarm-algorithm)
 - [String Search Algorithms for Large Texts](https://www.baeldung.com/java-full-text-search-algorithms)
@@ -7,3 +12,4 @@
 - [Find Substrings That Are Palindromes in Java](https://www.baeldung.com/java-palindrome-substrings)
 - [Find the Longest Substring without Repeating Characters](https://www.baeldung.com/java-longest-substring-without-repeated-characters)
 - [Permutations of an Array in Java](https://www.baeldung.com/java-array-permutations)
+- More articles: [[<-- prev]](/../algorithms-miscellaneous-3) [[next -->]](/../algorithms-miscellaneous-5)

algorithms-miscellaneous-5/README.md

@@ -1,5 +1,11 @@
-## Relevant articles:
+## Algorithms - Miscellaneous
+
+This module contains articles about algorithms. Some classes of algorithms, e.g., [sorting](/../algorithms-sorting) and
+[genetic algorithms](/../algorithms-genetic), have their own dedicated modules. 
+
+### Relevant articles:
 
 - [Converting Between Byte Arrays and Hexadecimal Strings in Java](https://www.baeldung.com/java-byte-arrays-hex-strings)
 - [Reversing a Binary Tree in Java](https://www.baeldung.com/java-reversing-a-binary-tree)
 - [Find If Two Numbers Are Relatively Prime in Java](https://www.baeldung.com/java-two-relatively-prime-numbers)
+- More articles: [[<-- prev]](/../algorithms-miscellaneous-4)

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/knapsack/Knapsack.java

@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.knapsack;
+
+public class Knapsack {
+
+    public int knapsackRec(int[] w, int[] v, int n, int W) {
+        if (n <= 0) {
+            return 0;
+        } else if (w[n - 1] > W) {
+            return knapsackRec(w, v, n - 1, W);
+        } else {
+            return Math.max(knapsackRec(w, v, n - 1, W), v[n - 1] + knapsackRec(w, v, n - 1, W - w[n - 1]));
+        }
+    }
+
+    public int knapsackDP(int[] w, int[] v, int n, int W) {
+        if (n <= 0 || W <= 0) {
+            return 0;
+        }
+
+        int[][] m = new int[n + 1][W + 1];
+        for (int j = 0; j <= W; j++) {
+            m[0][j] = 0;
+        }
+
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= W; j++) {
+                if (w[i - 1] > j) {
+                    m[i][j] = m[i - 1][j];
+                } else {
+                    m[i][j] = Math.max(m[i - 1][j], m[i - 1][j - w[i - 1]] + v[i - 1]);
+                }
+            }
+        }
+        return m[n][W];
+    }
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/knapsack/KnapsackUnitTest.java

@@ -0,0 +1,44 @@
+package com.baeldung.algorithms.knapsack;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class KnapsackUnitTest {
+
+    @Test
+    public void givenWeightsandValues_whenCalculateMax_thenOutputCorrectResult() {
+        final int[] w = new int[] { 23, 26, 20, 18, 32, 27, 29, 26, 30, 27 };
+        final int[] v = new int[] { 505, 352, 458, 220, 354, 414, 498, 545, 473, 543 };
+        final int n = 10;
+        final int W = 67;
+        final Knapsack knapsack = new Knapsack();
+
+        assertEquals(1270, knapsack.knapsackRec(w, v, n, W));
+        assertEquals(1270, knapsack.knapsackDP(w, v, n, W));
+    }
+
+    @Test
+    public void givenZeroItems_whenCalculateMax_thenOutputZero() {
+        final int[] w = new int[] {};
+        final int[] v = new int[] {};
+        final int n = 0;
+        final int W = 67;
+        final Knapsack knapsack = new Knapsack();
+
+        assertEquals(0, knapsack.knapsackRec(w, v, n, W));
+        assertEquals(0, knapsack.knapsackDP(w, v, n, W));
+    }
+
+    @Test
+    public void givenZeroWeightLimit_whenCalculateMax_thenOutputZero() {
+        final int[] w = new int[] { 23, 26, 20, 18, 32, 27, 29, 26, 30, 27 };
+        final int[] v = new int[] { 505, 352, 458, 220, 354, 414, 498, 545, 473, 543 };
+        final int n = 10;
+        final int W = 0;
+        final Knapsack knapsack = new Knapsack();
+
+        assertEquals(0, knapsack.knapsackRec(w, v, n, W));
+        assertEquals(0, knapsack.knapsackDP(w, v, n, W));
+    }
+}

algorithms-sorting/README.md

@@ -12,3 +12,8 @@ This module contains articles about sorting algorithms.
 - [Shell Sort in Java](https://www.baeldung.com/java-shell-sort)
 - [Counting Sort in Java](https://www.baeldung.com/java-counting-sort)
 - [Sorting Strings by Contained Numbers in Java](https://www.baeldung.com/java-sort-strings-contained-numbers)
+- [How an In-Place Sorting Algorithm Works](https://www.baeldung.com/java-in-place-sorting)
+- [Selection Sort in Java](https://www.baeldung.com/java-selection-sort)
+- [Sorting Strings by Contained Numbers in Java](https://www.baeldung.com/java-sort-strings-contained-numbers)
+- [Radix Sort in Java](https://www.baeldung.com/java-radix-sort)
+- [Sorting a String Alphabetically in Java](https://www.baeldung.com/java-sort-string-alphabetically)

algorithms-sorting/pom.xml

@@ -28,6 +28,12 @@
             <version>${lombok.version}</version>
             <scope>provided</scope>
         </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <version>${junit-jupiter-api.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
@@ -52,6 +58,7 @@
         <commons-math3.version>3.6.1</commons-math3.version>
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
         <commons-codec.version>1.11</commons-codec.version>
+        <junit-jupiter-api.version>5.3.1</junit-jupiter-api.version>
     </properties>
 
 </project>

algorithms-sorting/src/main/java/com/baeldung/algorithms/stringsort/AnagramValidator.java

@@ -1,4 +1,4 @@
-package com.baeldung.string.sorting;
+package com.baeldung.algorithms.stringsort;
 
 import java.util.Arrays;
 

algorithms-sorting/src/test/java/com/baeldung/algorithms/stringsort/AnagramValidatorUnitTest.java

@@ -1,12 +1,10 @@
-package com.baeldung.string.sorting;
+package com.baeldung.algorithms.stringsort;
 
 
-import static org.junit.jupiter.api.Assertions.assertTrue;
-import static org.junit.jupiter.api.Assertions.assertFalse;
-
 import org.junit.jupiter.api.Test;
 
-import com.baeldung.string.sorting.AnagramValidator;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 class AnagramValidatorUnitTest {
     

algorithms-sorting/src/test/java/com/baeldung/algorithms/stringsort/SortStringUnitTest.java

@@ -1,9 +1,9 @@
-package com.baeldung.string.sorting;
+package com.baeldung.algorithms.stringsort;
-
-import java.util.Arrays;
 
 import org.junit.jupiter.api.Test;
 
+import java.util.Arrays;
+
 import static org.assertj.core.api.Assertions.assertThat;
 
 class SortStringUnitTest {

animal-sniffer-mvn-plugin/pom.xml

@@ -1,7 +1,6 @@
 <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/maven-v4_0_0.xsd">
     <modelVersion>4.0.0</modelVersion>
-    <groupId>com.baeldung</groupId>
     <artifactId>animal-sniffer-mvn-plugin</artifactId>
     <version>1.0-SNAPSHOT</version>
     <name>animal-sniffer-mvn-plugin</name>

apache-avro/pom.xml

@@ -14,12 +14,6 @@
     </parent>
 
     <dependencies>
-        <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
-            <version>${junit.version}</version>
-            <scope>test</scope>
-        </dependency>
         <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-simple</artifactId>
@@ -46,15 +40,6 @@
 
     <build>
         <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <version>${compiler-plugin.version}</version>
-                <configuration>
-                    <source>${java.version}</source>
-                    <target>${java.version}</target>
-                </configuration>
-            </plugin>
             <plugin>
                 <groupId>org.apache.avro</groupId>
                 <artifactId>avro-maven-plugin</artifactId>
@@ -79,8 +64,6 @@
     </build>
 
     <properties>
-        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <compiler-plugin.version>3.5</compiler-plugin.version>
         <avro.version>1.8.2</avro.version>
         <slf4j.version>1.7.25</slf4j.version>
     </properties>

apache-fop/pom.xml

@@ -1,7 +1,6 @@
 <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</groupId>
     <artifactId>apache-fop</artifactId>
     <version>0.1-SNAPSHOT</version>
     <name>apache-fop</name>

apache-geode/pom.xml

@@ -19,26 +19,8 @@
             <artifactId>geode-core</artifactId>
             <version>${geode.core}</version>
         </dependency>
-        <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
-            <version>${junit.version}</version>
-        </dependency>
     </dependencies>
 	
-    <build>
-        <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <configuration>
-                    <source>${java.version}</source>
-                    <target>${java.version}</target>
-                </configuration>
-            </plugin>
-        </plugins>
-    </build>
-	
     <properties>
         <geode.core>1.6.0</geode.core>
     </properties>

apache-meecrowave/pom.xml

@@ -1,7 +1,6 @@
 <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</groupId>
     <artifactId>apache-meecrowave</artifactId>
     <version>0.0.1</version>
     <name>apache-meecrowave</name>
@@ -38,13 +37,6 @@
             <version>${meecrowave-junit.version}</version>
             <scope>test</scope>
         </dependency>
-        <!-- https://mvnrepository.com/artifact/junit/junit -->
-        <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
-            <version>${junit.version}</version>
-            <scope>test</scope>
-        </dependency>
     </dependencies>
 	
     <build>

apache-olingo/olingo2/pom.xml

@@ -5,7 +5,6 @@
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>org.baeldung.examples.olingo2</groupId>
 	<artifactId>olingo2</artifactId>
-	<version>0.0.1-SNAPSHOT</version>
 	<name>olingo2</name>
 	<description>Sample Olingo 2 Project</description>
 

apache-pulsar/pom.xml

@@ -24,8 +24,6 @@
     </dependencies>
 	
     <properties>
-        <maven.compiler.target>1.8</maven.compiler.target>
-        <maven.compiler.source>1.8</maven.compiler.source>
  		<pulsar-client.version>2.1.1-incubating</pulsar-client.version>
     </properties>
 </project>

apache-shiro/README.md

@@ -5,3 +5,5 @@ This module contains articles about Apache Shiro
 ### Relevant articles:
 
 - [Introduction to Apache Shiro](https://www.baeldung.com/apache-shiro)
+- [Permissions-Based Access Control with Apache Shiro](https://www.baeldung.com/apache-shiro-access-control)
+

apache-solrj/pom.xml

@@ -1,7 +1,6 @@
 <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</groupId>
     <artifactId>apache-solrj</artifactId>
     <version>0.0.1-SNAPSHOT</version>
     <name>apache-solrj</name>

apache-spark/README.md

@@ -6,3 +6,5 @@ This module contains articles about Apache Spark
 
 - [Introduction to Apache Spark](https://www.baeldung.com/apache-spark)
 - [Building a Data Pipeline with Kafka, Spark Streaming and Cassandra](https://www.baeldung.com/kafka-spark-data-pipeline)
+- [Machine Learning with Spark MLlib](https://www.baeldung.com/spark-mlib-machine-learning)
+

apache-spark/pom.xml

@@ -2,7 +2,6 @@
 	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</groupId>
 	<artifactId>apache-spark</artifactId>
 	<version>1.0-SNAPSHOT</version>
 	<name>apache-spark</name>
@@ -59,15 +58,6 @@
 
 	<build>
 		<plugins>
-			<plugin>
-				<groupId>org.apache.maven.plugins</groupId>
-				<artifactId>maven-compiler-plugin</artifactId>
-				<version>${maven-compiler-plugin.version}</version>
-				<configuration>
-					<source>${java.version}</source>
-					<target>${java.version}</target>
-				</configuration>
-			</plugin>
 			<plugin>
 				<artifactId>maven-assembly-plugin</artifactId>
 				<executions>
@@ -95,7 +85,6 @@
 		<org.apache.spark.spark-streaming-kafka.version>2.3.0</org.apache.spark.spark-streaming-kafka.version>
 		<com.datastax.spark.spark-cassandra-connector.version>2.3.0</com.datastax.spark.spark-cassandra-connector.version>
 		<com.datastax.spark.spark-cassandra-connector-java.version>1.5.2</com.datastax.spark.spark-cassandra-connector-java.version>
-		<maven-compiler-plugin.version>3.2</maven-compiler-plugin.version>
 	</properties>
 
 </project>

apache-velocity/pom.xml

@@ -1,7 +1,6 @@
 <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/maven-v4_0_0.xsd">
     <modelVersion>4.0.0</modelVersion>
-    <groupId>com.baeldung</groupId>
     <version>0.1-SNAPSHOT</version>
     <artifactId>apache-velocity</artifactId>
     <name>apache-velocity</name>

aws-lambda/pom.xml

@@ -2,7 +2,6 @@
 <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</groupId>
     <artifactId>aws-lambda</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>aws-lambda</name>
@@ -88,7 +87,6 @@
     
     <properties>
         <json-simple.version>1.1.1</json-simple.version>
-        <org.json.version>20180130</org.json.version>
         <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>1.2.0</aws-lambda-java-core.version>

aws/pom.xml

@@ -1,7 +1,6 @@
 <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</groupId>
     <artifactId>aws</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>aws</name>

axon/pom.xml

@@ -30,7 +30,6 @@
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-autoconfigure</artifactId>
-            <version>${spring-boot.version}</version>
             <scope>compile</scope>
         </dependency>
 

azure/pom.xml

@@ -2,7 +2,6 @@
 <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</groupId>
     <artifactId>azure</artifactId>
     <version>0.1</version>
     <name>azure</name>

blade/pom.xml

@@ -3,19 +3,14 @@
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
 
     <modelVersion>4.0.0</modelVersion>
-    <!-- WITH THIS mvn integration-test DOES WORK -->
-    <groupId>com.baeldung</groupId>
     <artifactId>blade</artifactId>
-    <version>1.0.0-SNAPSHOT</version>
     <name>blade</name>
 
-
+	<parent>
-    <!-- WITH THIS mvn integration-test DOESN'T WORK -->
+		<groupId>com.baeldung</groupId>
-    <!-- <parent> -->
+		<artifactId>parent-modules</artifactId>
-    <!-- <groupId>com.baeldung</groupId> -->
+		<version>1.0.0-SNAPSHOT</version>
-    <!-- <artifactId>parent-modules</artifactId> -->
+	</parent>
-    <!-- <version>1.0.0-SNAPSHOT</version> -->
-    <!-- </parent> -->
 
     <dependencies>
         <dependency>
@@ -45,12 +40,6 @@
         </dependency>
 
         <!-- TEST -->
-        <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
-            <version>${junit.version}</version>
-            <scope>test</scope>
-        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
@@ -79,20 +68,6 @@
     <build>
         <finalName>sample-blade-app</finalName>
         <plugins>
-
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-surefire-plugin</artifactId>
-                <version>${maven-surefire-plugin.version}</version>
-                <configuration>
-                    <forkCount>3</forkCount>
-                    <reuseForks>true</reuseForks>
-                    <excludes>
-                        <exclude>**/*LiveTest.java</exclude>
-                    </excludes>
-                </configuration>
-            </plugin>
-
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-failsafe-plugin</artifactId>
@@ -172,34 +147,19 @@
                     </execution>
                 </executions>
             </plugin>
-            <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>
-                    <encoding>UTF-8</encoding>
-                </configuration>
-            </plugin>
         </plugins>
     </build>
 	
     <properties>
-        <maven.compiler.source>1.8</maven.compiler.source>
-        <maven.compiler.target>1.8</maven.compiler.target>
 		<blade-mvc.version>2.0.14.RELEASE</blade-mvc.version>
 		<bootstrap.version>4.2.1</bootstrap.version>
 		<commons-lang3.version>3.8.1</commons-lang3.version>
 		<lombok.version>1.18.4</lombok.version>
-		<junit.version>4.12</junit.version>
 		<httpclient.version>4.5.6</httpclient.version>
 		<httpmime.version>4.5.6</httpmime.version>
 		<httpcore.version>4.4.10</httpcore.version>
 		<assertj-core.version>3.11.1</assertj-core.version>
 		<maven-failsafe-plugin.version>3.0.0-M3</maven-failsafe-plugin.version>
 		<process-exec-maven-plugin.version>0.7</process-exec-maven-plugin.version>
-		<maven-surefire-plugin.version>2.21.0</maven-surefire-plugin.version>
-		<maven-compiler-plugin.version>3.7.0</maven-compiler-plugin.version>
     </properties>
 </project>

bootique/pom.xml

@@ -42,12 +42,6 @@
             <artifactId>bootique-test</artifactId>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
-            <version>${junit.version}</version>
-            <scope>test</scope>
-        </dependency>
     </dependencies>
 
     <build>

cas/cas-server/pom.xml

@@ -198,7 +198,6 @@
 
         <wrapper-maven-plugin.version>0.0.4</wrapper-maven-plugin.version>
         <maven-war-plugin.version>2.6</maven-war-plugin.version>
-        <maven-compiler-plugin.version>3.3</maven-compiler-plugin.version>
         
         <echo-maven-plugin.version>0.3.0</echo-maven-plugin.version>
         <pgpverify-maven-plugin.version>1.1.0</pgpverify-maven-plugin.version>

cdi/pom.xml

@@ -36,12 +36,6 @@
             <version>${assertj-core.version}</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
-            <version>${junit.version}</version>
-            <scope>test</scope>
-        </dependency>
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-context</artifactId>

checker-plugin/pom.xml

@@ -1,7 +1,6 @@
 <project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
     <modelVersion>4.0.0</modelVersion>
-    <groupId>com.baeldung</groupId>
     <artifactId>checker-plugin</artifactId>
     <version>1.0-SNAPSHOT</version>
     <name>checker-plugin</name>

cloud-foundry-uaa/cf-uaa-oauth2-client/pom.xml

@@ -4,7 +4,6 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.example</groupId>
     <artifactId>cf-uaa-oauth2-client</artifactId>
-    <version>0.0.1-SNAPSHOT</version>
     <name>uaa-client-webapp</name>
     <description>Demo project for Spring Boot</description>
 

cloud-foundry-uaa/cf-uaa-oauth2-resource-server/pom.xml

@@ -4,7 +4,6 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.baeldung.cfuaa</groupId>
     <artifactId>cf-uaa-oauth2-resource-server</artifactId>
-    <version>0.0.1-SNAPSHOT</version>
     <name>cf-uaa-oauth2-resource-server</name>
     <description>Demo project for Spring Boot</description>
 

code-generation/pom.xml

@@ -1,7 +1,6 @@
 <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/maven-v4_0_0.xsd">
     <modelVersion>4.0.0</modelVersion>
-    <groupId>com.baeldung</groupId>
     <artifactId>code-generation</artifactId>
     <version>1.0</version>
     <name>code-generation</name>

core-groovy-2/README.md

@@ -11,4 +11,5 @@ This module contains articles about core Groovy concepts
 - [Integrating Groovy into Java Applications](https://www.baeldung.com/groovy-java-applications)
 - [Concatenate Strings with Groovy](https://www.baeldung.com/groovy-concatenate-strings)
 - [Metaprogramming in Groovy](https://www.baeldung.com/groovy-metaprogramming)
+- [A Quick Guide to Working with Web Services in Groovy](https://www.baeldung.com/groovy-web-services)
 - [[<-- Prev]](/core-groovy)

core-groovy-2/pom.xml

@@ -181,10 +181,8 @@
         <hsqldb.version>2.4.0</hsqldb.version>
         <spock-core.version>1.1-groovy-2.4</spock-core.version>
         <groovy-wslite.version>1.1.3</groovy-wslite.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>
-        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>
 </project>
 

core-groovy/pom.xml

@@ -109,9 +109,6 @@
 
     <properties>
         <junit.platform.version>1.0.0</junit.platform.version>
-<!--         <groovy.version>2.4.13</groovy.version> -->
-<!--         <groovy-all.version>2.4.13</groovy-all.version> -->
-<!--         <groovy-sql.version>2.4.13</groovy-sql.version> -->
         <groovy.version>2.5.6</groovy.version>
         <groovy-all.version>2.5.6</groovy-all.version>
         <groovy-sql.version>2.5.6</groovy-sql.version>

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

@@ -3,7 +3,6 @@
     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</groupId>
     <artifactId>core-java-8-2</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-8-2</name>
@@ -30,24 +29,7 @@
         </dependency>
     </dependencies>
 
-    <build>
-        <plugins>
-            <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>
-                </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>

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

@@ -1,7 +1,6 @@
 <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</groupId>
     <artifactId>core-java-8</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-8</name>
@@ -20,31 +19,11 @@
             <artifactId>commons-collections4</artifactId>
             <version>${commons-collections4.version}</version>
         </dependency>
-        <dependency>
-            <groupId>commons-io</groupId>
-            <artifactId>commons-io</artifactId>
-            <version>${commons-io.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.apache.commons</groupId>
-            <artifactId>commons-lang3</artifactId>
-            <version>${commons-lang3.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.apache.commons</groupId>
-            <artifactId>commons-math3</artifactId>
-            <version>${commons-math3.version}</version>
-        </dependency>
         <dependency>
             <groupId>log4j</groupId>
             <artifactId>log4j</artifactId>
             <version>${log4j.version}</version>
         </dependency>
-        <dependency>
-            <groupId>commons-codec</groupId>
-            <artifactId>commons-codec</artifactId>
-            <version>${commons-codec.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.projectlombok</groupId>
             <artifactId>lombok</artifactId>
@@ -58,64 +37,6 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>com.jayway.awaitility</groupId>
-            <artifactId>awaitility</artifactId>
-            <version>${avaitility.version}</version>
-            <scope>test</scope>
-        </dependency>
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-core</artifactId>
-            <version>${jmh-core.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-generator-annprocess</artifactId>
-            <version>${jmh-generator.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-generator-bytecode</artifactId>
-            <version>${jmh-generator.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.codepoetics</groupId>
-            <artifactId>protonpack</artifactId>
-            <version>${protonpack.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>io.vavr</groupId>
-            <artifactId>vavr</artifactId>
-            <version>${vavr.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>joda-time</groupId>
-            <artifactId>joda-time</artifactId>
-            <version>${joda.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.aspectj</groupId>
-            <artifactId>aspectjrt</artifactId>
-            <version>${asspectj.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.aspectj</groupId>
-            <artifactId>aspectjweaver</artifactId>
-            <version>${asspectj.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.powermock</groupId>
-            <artifactId>powermock-module-junit4</artifactId>
-            <version>${powermock.version}</version>
-            <scope>test</scope>
-        </dependency>
-        <dependency>
-            <groupId>org.powermock</groupId>
-            <artifactId>powermock-api-mockito2</artifactId>
-            <version>${powermock.version}</version>
-            <scope>test</scope>
-        </dependency>
     </dependencies>
 
     <build>
@@ -149,22 +70,10 @@
 
     <properties>
         <!-- util -->
-        <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>
-        <commons-codec.version>1.10</commons-codec.version>
-        <vavr.version>0.9.0</vavr.version>
-        <protonpack.version>1.13</protonpack.version>
-        <joda.version>2.10</joda.version>
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
-        <asspectj.version>1.8.9</asspectj.version>
-        <powermock.version>2.0.0-RC.4</powermock.version>
-        <avaitility.version>1.7.0</avaitility.version>
-        <jmh-core.version>1.19</jmh-core.version>
-        <jmh-generator.version>1.19</jmh-generator.version>
-        <spring-boot-maven-plugin.version>2.0.4.RELEASE</spring-boot-maven-plugin.version>
         <!-- plugins -->
-        <maven-surefire-plugin.version>2.22.1</maven-surefire-plugin.version>
+        <spring-boot-maven-plugin.version>2.0.4.RELEASE</spring-boot-maven-plugin.version>
     </properties>
 </project>

core-java-modules/core-java-8/src/main/java/com/baeldung/java_8_features/groupingby/Tuple.java

@@ -1,12 +1,12 @@
 package com.baeldung.java_8_features.groupingby;
 
-public class Tuple {
+import java.util.Objects;
 
-    private BlogPostType type;
+public class Tuple {
-    private String author;
+    private final BlogPostType type;
+    private final String author;
 
     public Tuple(BlogPostType type, String author) {
-        super();
         this.type = type;
         this.author = author;
     }
@@ -15,20 +15,27 @@ public class Tuple {
         return type;
     }
 
-    public void setType(BlogPostType type) {
-        this.type = type;
-    }
-
     public String getAuthor() {
         return author;
     }
 
-    public void setAuthor(String author) {
+    @Override
-        this.author = author;
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        Tuple tuple = (Tuple) o;
+        return type == tuple.type && author.equals(tuple.author);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(type, author);
     }
 
     @Override
     public String toString() {
-        return "Tuple [type=" + type + ", author=" + author + ", getType()=" + getType() + ", getAuthor()=" + getAuthor() + ", getClass()=" + getClass() + ", hashCode()=" + hashCode() + ", toString()=" + super.toString() + "]";
+        return "Tuple{" + "type=" + type + ", author='" + author + '\'' + '}';
     }
 }

core-java-modules/core-java-8/src/test/java/com/baeldung/java_8_features/groupingby/Java8GroupingByCollectorUnitTest.java

@@ -1,15 +1,32 @@
 package com.baeldung.java_8_features.groupingby;
 
-import com.baeldung.java_8_features.groupingby.BlogPost;
+import static java.util.Comparator.comparingInt;
-import com.baeldung.java_8_features.groupingby.BlogPostType;
+import static java.util.stream.Collectors.averagingInt;
-import org.junit.Test;
+import static java.util.stream.Collectors.counting;
+import static java.util.stream.Collectors.groupingBy;
+import static java.util.stream.Collectors.groupingByConcurrent;
+import static java.util.stream.Collectors.joining;
+import static java.util.stream.Collectors.mapping;
+import static java.util.stream.Collectors.maxBy;
+import static java.util.stream.Collectors.summarizingInt;
+import static java.util.stream.Collectors.summingInt;
+import static java.util.stream.Collectors.toList;
+import static java.util.stream.Collectors.toSet;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
 
-import java.util.*;
+import java.util.Arrays;
+import java.util.EnumMap;
+import java.util.IntSummaryStatistics;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
 import java.util.concurrent.ConcurrentMap;
 
-import static java.util.Comparator.comparingInt;
+import org.junit.Test;
-import static java.util.stream.Collectors.*;
-import static org.junit.Assert.*;
 
 public class Java8GroupingByCollectorUnitTest {
 
@@ -180,4 +197,19 @@ public class Java8GroupingByCollectorUnitTest {
         assertEquals(15, newsLikeStatistics.getMin());
     }
 
+    @Test
+    public void givenAListOfPosts_whenGroupedByComplexMapKeyType_thenGetAMapBetweenTupleAndList() {
+        Map<Tuple, List<BlogPost>> postsPerTypeAndAuthor = posts.stream()
+            .collect(groupingBy(post -> new Tuple(post.getType(), post.getAuthor())));
+
+        List<BlogPost> result = postsPerTypeAndAuthor.get(new Tuple(BlogPostType.GUIDE, "Author 1"));
+
+        assertThat(result.size()).isEqualTo(1);
+
+        BlogPost blogPost = result.get(0);
+
+        assertThat(blogPost.getTitle()).isEqualTo("Programming guide");
+        assertThat(blogPost.getType()).isEqualTo(BlogPostType.GUIDE);
+        assertThat(blogPost.getAuthor()).isEqualTo("Author 1");
+    }
 }

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

@@ -1,7 +1,6 @@
 <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</groupId>
     <artifactId>core-java-annotations</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-annotations</name>
@@ -14,42 +13,6 @@
         <relativePath>../../parent-java</relativePath>
     </parent>
 
-    <dependencies>
-        <dependency>
-            <groupId>org.apache.commons</groupId>
-            <artifactId>commons-lang3</artifactId>
-            <version>${commons-lang3.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.projectlombok</groupId>
-            <artifactId>lombok</artifactId>
-            <version>${lombok.version}</version>
-            <scope>provided</scope>
-        </dependency>
-        <!-- test scoped -->
-        <dependency>
-            <groupId>org.assertj</groupId>
-            <artifactId>assertj-core</artifactId>
-            <version>${assertj.version}</version>
-            <scope>test</scope>
-        </dependency>
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-core</artifactId>
-            <version>${jmh-core.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-generator-annprocess</artifactId>
-            <version>${jmh-generator.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-generator-bytecode</artifactId>
-            <version>${jmh-generator.version}</version>
-        </dependency>
-    </dependencies>
-
     <build>
         <finalName>core-java-annotations</finalName>
         <resources>
@@ -60,13 +23,4 @@
         </resources>
     </build>
 
-    <properties>
-        <!-- testing -->
-        <assertj.version>3.6.1</assertj.version>
-        <asspectj.version>1.8.9</asspectj.version>
-        <jmh-core.version>1.19</jmh-core.version>
-        <jmh-generator.version>1.19</jmh-generator.version>
-        <!-- plugins -->
-        <maven-surefire-plugin.version>2.22.1</maven-surefire-plugin.version>
-    </properties>
 </project>

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

@@ -1,7 +1,6 @@
 <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</groupId>
     <artifactId>core-java-arrays-2</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-arrays-2</name>

core-java-modules/core-java-arrays-2/src/main/java/com/baeldung/array/operations/ArrayOperations.java

@@ -193,14 +193,47 @@ public class ArrayOperations {
     }
 
     public static Integer[] intersectionSimple(final Integer[] a, final Integer[] b) {
-        return Stream.of(a).filter(Arrays.asList(b)::contains).toArray(Integer[]::new);
+        return Stream.of(a)
+            .filter(Arrays.asList(b)::contains)
+            .toArray(Integer[]::new);
     }
 
     public static Integer[] intersectionSet(final Integer[] a, final Integer[] b) {
-        return Stream.of(a).filter(Arrays.asList(b)::contains).distinct().toArray(Integer[]::new);
+        return Stream.of(a)
+            .filter(Arrays.asList(b)::contains)
+            .distinct()
+            .toArray(Integer[]::new);
     }
 
     public static Integer[] intersectionMultiSet(final Integer[] a, final Integer[] b) {
-        return Stream.of(a).filter(new LinkedList<>(Arrays.asList(b))::remove).toArray(Integer[]::new);
+        return Stream.of(a)
+            .filter(new LinkedList<>(Arrays.asList(b))::remove)
+            .toArray(Integer[]::new);
+    }
+
+    public static Integer[] addElementUsingPureJava(Integer[] srcArray, int elementToAdd) {
+        Integer[] destArray = new Integer[srcArray.length + 1];
+
+        for (int i = 0; i < srcArray.length; i++) {
+            destArray[i] = srcArray[i];
+        }
+
+        destArray[destArray.length - 1] = elementToAdd;
+        return destArray;
+    }
+
+    public static int[] insertAnElementAtAGivenIndex(final int[] srcArray, int index, int newElement) {
+        int[] destArray = new int[srcArray.length + 1];
+        int j = 0;
+        for (int i = 0; i < destArray.length - 1; i++) {
+
+            if (i == index) {
+                destArray[i] = newElement;
+            } else {
+                destArray[i] = srcArray[j];
+                j++;
+            }
+        }
+        return destArray;
     }
 }

core-java-modules/core-java-arrays-2/src/main/java/com/baeldung/arraylist/operations/ArrayListOperations.java

@@ -0,0 +1,23 @@
+package com.baeldung.arraylist.operations;
+
+import java.util.ArrayList;
+
+public class ArrayListOperations {
+
+    public static Integer getAnIntegerElement(ArrayList<Integer> anArrayList, int index) {
+        return anArrayList.get(index);
+    }
+
+    public static void modifyAnIntegerElement(ArrayList<Integer> anArrayList, int index, Integer newElement) {
+        anArrayList.set(index, newElement);
+    }
+
+    public static void appendAnIntegerElement(ArrayList<Integer> anArrayList, Integer newElement) {
+        anArrayList.add(newElement);
+    }
+
+    public static void insertAnIntegerElementAtIndex(ArrayList<Integer> anArrayList, int index, Integer newElement) {
+        anArrayList.add(index, newElement);
+    }
+
+}

core-java-modules/core-java-arrays-2/src/test/java/com/baeldung/array/operations/ArrayOperationsUnitTest.java

@@ -1,12 +1,11 @@
 package com.baeldung.array.operations;
 
+import java.util.Arrays;
 import org.assertj.core.api.Condition;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-
-import java.util.Arrays;
-
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertArrayEquals;
 
 public class ArrayOperationsUnitTest {
 
@@ -262,8 +261,7 @@ public class ArrayOperationsUnitTest {
 
     @Test
     public void whenMapIntArrayToString_thenReturnArray() {
-        String[] expectedArray = new String[] { "Value: 3", "Value: 5", "Value: 2", "Value: 5", "Value: 14",
+        String[] expectedArray = new String[] { "Value: 3", "Value: 5", "Value: 2", "Value: 5", "Value: 14", "Value: 4" };
-                "Value: 4" };
         String[] output = ArrayOperations.mapIntArrayToString(defaultIntArray);
 
         assertThat(output).containsExactly(expectedArray);
@@ -313,13 +311,10 @@ public class ArrayOperationsUnitTest {
         int[] output5 = ArrayOperations.shuffleIntArray(defaultIntArray);
         int[] output6 = ArrayOperations.shuffleIntArray(defaultIntArray);
 
-        Condition<int[]> atLeastOneArraysIsNotEqual = new Condition<int[]>(
+        Condition<int[]> atLeastOneArraysIsNotEqual = new Condition<int[]>("at least one output should be different (order-wise)") {
-            "at least one output should be different (order-wise)") {
             @Override
             public boolean matches(int[] value) {
-                return !Arrays.equals(value, output) || !Arrays.equals(value, output2) || !Arrays.equals(value, output3)
+                return !Arrays.equals(value, output) || !Arrays.equals(value, output2) || !Arrays.equals(value, output3) || !Arrays.equals(value, output4) || !Arrays.equals(value, output5) || !Arrays.equals(value, output6);
-                    || !Arrays.equals(value, output4) || !Arrays.equals(value, output5)
-                    || !Arrays.equals(value, output6);
             }
         };
 
@@ -335,13 +330,10 @@ public class ArrayOperationsUnitTest {
         Integer[] output5 = ArrayOperations.shuffleObjectArray(defaultObjectArray);
         Integer[] output6 = ArrayOperations.shuffleObjectArray(defaultObjectArray);
 
-        Condition<Integer[]> atLeastOneArraysIsNotEqual = new Condition<Integer[]>(
+        Condition<Integer[]> atLeastOneArraysIsNotEqual = new Condition<Integer[]>("at least one output should be different (order-wise)") {
-            "at least one output should be different (order-wise)") {
             @Override
             public boolean matches(Integer[] value) {
-                return !Arrays.equals(value, output) || !Arrays.equals(value, output2) || !Arrays.equals(value, output3)
+                return !Arrays.equals(value, output) || !Arrays.equals(value, output2) || !Arrays.equals(value, output3) || !Arrays.equals(value, output4) || !Arrays.equals(value, output5) || !Arrays.equals(value, output6);
-                    || !Arrays.equals(value, output4) || !Arrays.equals(value, output5)
-                    || !Arrays.equals(value, output6);
             }
         };
 
@@ -362,4 +354,27 @@ public class ArrayOperationsUnitTest {
 
         assertThat(defaultObjectArray).contains(output);
     }
+
+    @Test
+    public void givenSourceArrayAndElement_whenAddElementUsingPureJavaIsInvoked_thenNewElementMustBeAdded() {
+        Integer[] sourceArray = { 1, 2, 3, 4 };
+        int elementToAdd = 5;
+
+        Integer[] destArray = ArrayOperations.addElementUsingPureJava(sourceArray, elementToAdd);
+
+        Integer[] expectedArray = { 1, 2, 3, 4, 5 };
+        assertArrayEquals(expectedArray, destArray);
+    }
+
+    @Test
+    public void whenInsertAnElementAtAGivenIndexCalled_thenShiftTheFollowingElementsAndInsertTheElementInArray() {
+        int[] expectedArray = { 1, 4, 2, 3, 0 };
+        int[] anArray = new int[4];
+        anArray[0] = 1;
+        anArray[1] = 2;
+        anArray[2] = 3;
+        int[] outputArray = ArrayOperations.insertAnElementAtAGivenIndex(anArray, 1, 4);
+
+        assertThat(outputArray).containsExactly(expectedArray);
+    }
 }

core-java-modules/core-java-arrays-2/src/test/java/com/baeldung/arraylist/operations/ArrayListOperationsUnitTest.java

@@ -0,0 +1,50 @@
+package com.baeldung.arraylist.operations;
+
+import java.util.ArrayList;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ArrayListOperationsUnitTest {
+
+    private ArrayList<Integer> anArrayList;
+
+    @BeforeEach
+    public void setupDefaults() {
+        anArrayList = new ArrayList<>();
+        anArrayList.add(2);
+        anArrayList.add(3);
+        anArrayList.add(4);
+    }
+
+    @Test
+    public void whenGetAnIntegerElementCalled_thenReturnTheIntegerElement() {
+        Integer output = ArrayListOperations.getAnIntegerElement(anArrayList, 1);
+
+        assertThat(output).isEqualTo(3);
+    }
+
+    @Test
+    public void whenModifyAnIntegerElementCalled_thenModifyTheIntegerElement() {
+        ArrayListOperations.modifyAnIntegerElement(anArrayList, 2, 5);
+        Integer output = ArrayListOperations.getAnIntegerElement(anArrayList, 2);
+
+        assertThat(output).isEqualTo(5);
+    }
+
+    @Test
+    public void whenAppendAnIntegerElementCalled_thenTheIntegerElementIsAppendedToArrayList() {
+        ArrayListOperations.appendAnIntegerElement(anArrayList, 6);
+        Integer output = ArrayListOperations.getAnIntegerElement(anArrayList, anArrayList.size() - 1);
+
+        assertThat(output).isEqualTo(6);
+    }
+
+    @Test
+    public void whenInsertAnIntegerAtIndexCalled_thenTheIntegerElementIsInseredToArrayList() {
+        ArrayListOperations.insertAnIntegerElementAtIndex(anArrayList, 1, 10);
+        Integer output = ArrayListOperations.getAnIntegerElement(anArrayList, 1);
+
+        assertThat(output).isEqualTo(10);
+    }
+}

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

@@ -1,7 +1,6 @@
 <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</groupId>
     <artifactId>core-java-arrays</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-arrays</name>
@@ -20,16 +19,6 @@
             <artifactId>commons-lang3</artifactId>
             <version>${commons-lang3.version}</version>
         </dependency>
-        <dependency>
-            <groupId>log4j</groupId>
-            <artifactId>log4j</artifactId>
-            <version>${log4j.version}</version>
-        </dependency>
-        <dependency> <!-- needed to bridge to slf4j for projects that use the log4j APIs directly -->
-            <groupId>org.slf4j</groupId>
-            <artifactId>log4j-over-slf4j</artifactId>
-            <version>${org.slf4j.version}</version>
-        </dependency>
         <!-- test scoped -->
         <dependency>
             <groupId>org.assertj</groupId>
@@ -47,11 +36,6 @@
             <artifactId>jmh-generator-annprocess</artifactId>
             <version>${jmh-generator-annprocess.version}</version>
         </dependency>
-        <dependency>
-            <groupId>org.springframework</groupId>
-            <artifactId>spring-web</artifactId>
-            <version>${springframework.spring-web.version}</version>
-        </dependency>
     </dependencies>
 
     <build>
@@ -64,21 +48,6 @@
         </resources>
 
         <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-surefire-plugin</artifactId>
-                <configuration>
-                    <excludes>
-                        <exclude>**/*LiveTest.java</exclude>
-                        <exclude>**/*IntegrationTest.java</exclude>
-                        <exclude>**/*IntTest.java</exclude>
-                        <exclude>**/*LongRunningUnitTest.java</exclude>
-                        <exclude>**/*ManualTest.java</exclude>
-                    </excludes>
-                    <testFailureIgnore>true</testFailureIgnore>
-                </configuration>
-            </plugin>
-
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-dependency-plugin</artifactId>
@@ -398,8 +367,6 @@
         <assertj-core.version>3.10.0</assertj-core.version>
 
         <!-- maven and spring plugins -->
-        <maven-surefire-plugin.version>2.21.0</maven-surefire-plugin.version>
-        <springframework.spring-web.version>4.3.4.RELEASE</springframework.spring-web.version>
         <maven-javadoc-plugin.version>3.0.0-M1</maven-javadoc-plugin.version>
         <maven-jar-plugin.version>3.0.2</maven-jar-plugin.version>
         <onejar-maven-plugin.version>1.4.4</onejar-maven-plugin.version>

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

@@ -2,7 +2,6 @@
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <artifactId>core-java-collections-2</artifactId>
-    <version>0.0.1-SNAPSHOT</version>
     <name>core-java-collections-2</name>
     <packaging>jar</packaging>
 

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

@@ -8,3 +8,5 @@ This module contains articles about the Java ArrayList collection
 - [Add Multiple Items to an Java ArrayList](http://www.baeldung.com/java-add-items-array-list)
 - [ClassCastException: Arrays$ArrayList cannot be cast to ArrayList](https://www.baeldung.com/java-classcastexception-arrays-arraylist)
 - [Multi Dimensional ArrayList in Java](https://www.baeldung.com/java-multi-dimensional-arraylist)
+- [Removing an Element From an ArrayList](https://www.baeldung.com/java-arraylist-remove-element)
+

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

@@ -19,28 +19,16 @@
             <artifactId>commons-collections4</artifactId>
             <version>${commons-collections4.version}</version>
         </dependency>
-        <dependency>
-            <groupId>org.apache.commons</groupId>
-            <artifactId>commons-lang3</artifactId>
-            <version>${commons-lang3.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>org.projectlombok</groupId>
-            <artifactId>lombok</artifactId>
-            <version>${lombok.version}</version>
-            <scope>provided</scope>
-        </dependency>
     </dependencies>
 
     <properties>
         <commons-collections4.version>4.1</commons-collections4.version>
-        <commons-lang3.version>3.8.1</commons-lang3.version>
         <assertj.version>3.11.1</assertj.version>
     </properties>
 </project>

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

@@ -19,11 +19,6 @@
             <artifactId>commons-collections4</artifactId>
             <version>${commons-collections4.version}</version>
         </dependency>
-        <dependency>
-            <groupId>org.apache.commons</groupId>
-            <artifactId>commons-lang3</artifactId>
-            <version>${commons-lang3.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
@@ -40,7 +35,6 @@
 
     <properties>
         <commons-collections4.version>4.1</commons-collections4.version>    
-        <commons-lang3.version>3.8.1</commons-lang3.version>
         <assertj.version>3.11.1</assertj.version>
     </properties>
 </project>

core-java-modules/core-java-collections-list-2/src/main/java/com/baeldung/findastring/FindAStringInGivenList.java

@@ -0,0 +1,72 @@
+package com.baeldung.findastring;
+
+import com.google.common.base.Predicates;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+import org.apache.commons.collections4.IterableUtils;
+import org.apache.commons.collections4.IteratorUtils;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+public class FindAStringInGivenList {
+
+
+    public List<String> findUsingLoopWithRegex(String search, List<String> list) {
+
+        List<String> matches = new ArrayList<String>();
+
+        String pattern = ".*"+search+".*";
+        Pattern p = Pattern.compile(pattern);
+
+        for(String str: list) {
+            if (p.matcher(str).matches()) {
+                matches.add(str);
+            }
+        }
+
+        return matches;
+    }
+
+
+    public List<String> findUsingLoop(String search, List<String> list) {
+
+        List<String> matches = new ArrayList<String>();
+
+        for(String str: list) {
+            if (str.contains(search)) {
+                matches.add(str);
+            }
+        }
+
+        return matches;
+    }
+
+    public List<String> findUsingStream(String search, List<String> list) {
+
+        List<String> matchingElements =
+                list.stream()
+                        .filter(str -> str.trim().contains(search))
+                        .collect(Collectors.toList());
+
+        return matchingElements;
+    }
+
+    public List<String> findUsingGuava(String search, List<String> list) {
+        Iterable<String> result = Iterables.filter(list, Predicates.containsPattern(search));
+
+        return Lists.newArrayList(result.iterator());
+    }
+
+    public List<String> findUsingCommonsCollection(String search, List<String> list) {
+        Iterable<String> result = IterableUtils.filteredIterable(list, new org.apache.commons.collections4.Predicate<String>() {
+            public boolean evaluate(String listElement) {
+                return listElement.contains(search);
+            }
+        });
+
+        return IteratorUtils.toList(result.iterator());
+    }
+
+}

core-java-modules/core-java-collections-list-2/src/test/java/com/baeldung/findastring/FindAStringInListUnitTest.java

@@ -0,0 +1,62 @@
+package com.baeldung.findastring;
+
+import java.util.ArrayList;
+import java.util.List;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.Test;
+public class FindAStringInListUnitTest {
+
+    private static List<String> list = new ArrayList<>();
+
+    static {
+        list.add("Jack and Jill");
+        list.add("James and Sarah");
+        list.add("Sam and Louise");
+        list.add("Jack");
+        list.add("");
+    }
+
+    private static FindAStringInGivenList findAStringInGivenList = new FindAStringInGivenList();
+
+    @Test
+    public void givenAString_whenFoundUsingLoopWithRegex_thenReturnList() {
+        List matchingElements = findAStringInGivenList.findUsingLoopWithRegex("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+    @Test
+    public void givenAString_whenFoundUsingLoop_thenReturnList() {
+        List matchingElements = findAStringInGivenList.findUsingLoop("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+
+    @Test
+    public void givenAString_whenFoundUsingStream_thenReturnList(){
+        List matchingElements = findAStringInGivenList.findUsingStream("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+    @Test
+    public void givenAString_whenFoundUsingCommonsCollection_thenReturnList(){
+        List matchingElements = findAStringInGivenList.findUsingCommonsCollection("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+    @Test
+    public void givenAString_whenFoundUsingGuava_thenReturnList(){
+        List matchingElements = findAStringInGivenList.findUsingGuava("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+}

core-java-modules/core-java-collections-list-3/pom.xml

@@ -19,23 +19,12 @@
             <artifactId>commons-collections4</artifactId>
             <version>${commons-collections4.version}</version>
         </dependency>
-        <dependency>
-            <groupId>org.apache.commons</groupId>
-            <artifactId>commons-lang3</artifactId>
-            <version>${commons-lang3.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>org.projectlombok</groupId>
-            <artifactId>lombok</artifactId>
-            <version>${lombok.version}</version>
-            <scope>provided</scope>
-        </dependency>
 
         <dependency>
             <groupId>net.sf.trove4j</groupId>
@@ -67,7 +56,6 @@
 
     <properties>
         <commons-collections4.version>4.1</commons-collections4.version>
-        <commons-lang3.version>3.8.1</commons-lang3.version>
         <assertj.version>3.11.1</assertj.version>
 		<trove4j.version>3.0.2</trove4j.version>
 		<fastutil.version>8.1.0</fastutil.version>

core-java-modules/core-java-collections-list-3/src/main/java/com/baeldung/list/DuplicatesCounter.java

@@ -0,0 +1,42 @@
+package com.baeldung.list;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+/**
+ * Demo different approaches to get count of duplicated elements in an
+ * arrayList
+ */
+public class DuplicatesCounter {
+
+    public static <T> Map<T, Long> countByClassicalLoop(List<T> inputList) {
+        Map<T, Long> resultMap = new HashMap<>();
+        for (T element : inputList) {
+            if (resultMap.containsKey(element)) {
+                resultMap.put(element, resultMap.get(element) + 1L);
+            } else {
+                resultMap.put(element, 1L);
+            }
+        }
+        return resultMap;
+    }
+
+    public static <T> Map<T, Long> countByClassicalLoopWithMapCompute(List<T> inputList) {
+        Map<T, Long> resultMap = new HashMap<>();
+        for (T element : inputList) {
+            resultMap.compute(element, (k, v) -> v == null ? 1 : v + 1);
+        }
+        return resultMap;
+    }
+
+    public static <T> Map<T, Long> countByStreamToMap(List<T> inputList) {
+        return inputList.stream().collect(Collectors.toMap(Function.identity(), v -> 1L, Long::sum));
+    }
+
+    public static <T> Map<T, Long> countByStreamGroupBy(List<T> inputList) {
+        return inputList.stream().collect(Collectors.groupingBy(k -> k, Collectors.counting()));
+    }
+}

core-java-modules/core-java-collections-list-3/src/test/java/com/baeldung/list/DuplicatesCounterUnitTest.java

@@ -0,0 +1,55 @@
+package com.baeldung.list;
+
+import org.assertj.core.util.Lists;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.data.MapEntry.entry;
+
+class DuplicatesCounterUnitTest {
+
+
+    private static List<String> INPUT_LIST = Lists.list(
+        "expect1",
+        "expect2", "expect2",
+        "expect3", "expect3", "expect3",
+        "expect4", "expect4", "expect4", "expect4");
+
+    @Test
+    void givenInput_whenCountByClassicalLoop_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByClassicalLoop(INPUT_LIST);
+        verifyResult(result);
+    }
+
+
+    @Test
+    void givenInput_whenCountByClassicalLoopWithMapCompute_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByClassicalLoopWithMapCompute(INPUT_LIST);
+        verifyResult(result);
+    }
+
+    @Test
+    void givenInput_whenCountByStreamToMap_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByStreamToMap(INPUT_LIST);
+        verifyResult(result);
+    }
+
+    @Test
+    void givenInput_whenCountByStreamGroupBy_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByStreamGroupBy(INPUT_LIST);
+        verifyResult(result);
+    }
+
+    private void verifyResult(Map<String, Long> resultMap) {
+        assertThat(resultMap)
+            .isNotEmpty().hasSize(4)
+            .containsExactly(
+                entry("expect1", 1L),
+                entry("expect2", 2L),
+                entry("expect3", 3L),
+                entry("expect4", 4L));
+    }
+}

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

@@ -30,18 +30,11 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>org.projectlombok</groupId>
-            <artifactId>lombok</artifactId>
-            <version>${lombok.version}</version>
-            <scope>provided</scope>
-        </dependency>
     </dependencies>
 
     <properties>
         <commons-collections4.version>4.1</commons-collections4.version>
         <commons-lang3.version>3.8.1</commons-lang3.version>
         <assertj.version>3.11.1</assertj.version>
-		<trove4j.version>3.0.2</trove4j.version>
     </properties>
 </project>

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

@@ -14,11 +14,6 @@
     </parent>
 
     <dependencies>
-        <dependency>
-            <groupId>com.google.guava</groupId>
-            <artifactId>guava</artifactId>
-            <version>${guava.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-collections4</artifactId>
@@ -38,7 +33,6 @@
 
     <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-collections/pom.xml

@@ -30,12 +30,6 @@
             <artifactId>jmh-generator-annprocess</artifactId>
             <version>${openjdk.jmh.version}</version>
         </dependency>
-        <dependency>
-            <groupId>org.projectlombok</groupId>
-            <artifactId>lombok</artifactId>
-            <version>${lombok.version}</version>
-            <scope>provided</scope>
-        </dependency>
     </dependencies>
 
     <properties>

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

@@ -0,0 +1,19 @@
+=========
+
+## Core Java Concurrency Advanced Examples
+
+This module contains articles about advanced topics about multithreading with core Java.
+
+### Relevant Articles: 
+- [Semaphores in Java](https://www.baeldung.com/java-semaphore)
+- [Daemon Threads in Java](https://www.baeldung.com/java-daemon-thread)
+- [Priority-based Job Scheduling in Java](https://www.baeldung.com/java-priority-job-schedule)
+- [Brief Introduction to Java Thread.yield()](https://www.baeldung.com/java-thread-yield)
+- [Print Even and Odd Numbers Using 2 Threads](https://www.baeldung.com/java-even-odd-numbers-with-2-threads)
+- [Java CyclicBarrier vs CountDownLatch](https://www.baeldung.com/java-cyclicbarrier-countdownlatch)
+- [Guide to the Fork/Join Framework in Java](https://www.baeldung.com/java-fork-join)
+- [Guide to ThreadLocalRandom in Java](https://www.baeldung.com/java-thread-local-random)
+- [The Thread.join() Method in Java](https://www.baeldung.com/java-thread-join)
+- [Passing Parameters to Java Threads](https://www.baeldung.com/java-thread-parameters)
+
+[[<-- previous]](/core-java-modules/core-java-concurrency-advanced)[[next -->]](/core-java-modules/core-java-concurrency-advanced-3)

core-java-modules/core-java-concurrency-advanced-2/pom.xml

@@ -0,0 +1,59 @@
+<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</groupId>
+    <artifactId>core-java-concurrency-advanced-2</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-concurrency-advanced-2</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh-core.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh-generator-annprocess.version}</version>
+        </dependency>
+        
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-concurrency-advanced-2</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+        <jmh-core.version>1.19</jmh-core.version>
+        <jmh-generator-annprocess.version>1.19</jmh-generator-annprocess.version>
+        
+        <assertj.version>3.6.1</assertj.version>
+    </properties>
+
+</project>

core-java-modules/core-java-concurrency-advanced-2/src/main/java/com/baeldung/concurrent/cyclicbarrier/CyclicBarrierResetExample.java

@@ -4,6 +4,7 @@ import java.util.concurrent.BrokenBarrierException;
 import java.util.concurrent.CyclicBarrier;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 
 public class CyclicBarrierResetExample {
@@ -36,6 +37,11 @@ public class CyclicBarrierResetExample {
             });
         }
         es.shutdown();
+        try {
+            es.awaitTermination(1, TimeUnit.SECONDS);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
         return updateCount.get();
     }
 

core-java-modules/core-java-concurrency-advanced-2/src/main/java/com/baeldung/concurrent/daemon/NewThread.java

@@ -0,0 +1,23 @@
+package com.baeldung.concurrent.daemon;
+
+public class NewThread extends Thread {
+    public void run() {
+    	long startTime = System.currentTimeMillis();
+        while (true) {
+            for (int i = 0; i < 10; i++) {
+                System.out.println(this.getName() + ": New Thread is running..." + i);
+                try {
+                    //Wait for one sec so it doesn't print too fast
+                    Thread.sleep(1000);
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
+                }
+            }
+            // prevent the Thread to run forever. It will finish it's execution after 2 seconds
+            if (System.currentTimeMillis() - startTime > 2000) {
+            	Thread.currentThread().interrupt();
+            	break;
+            }
+        }
+    }
+}

core-java-modules/core-java-concurrency-advanced-2/src/main/java/com/baeldung/concurrent/parameters/AverageCalculator.java

@@ -1,4 +1,4 @@
-package com.baeldung.concurrent.parameter;
+package com.baeldung.concurrent.parameters;
 
 import java.util.concurrent.Callable;
 import java.util.stream.IntStream;

core-java-modules/core-java-concurrency-advanced-2/src/main/java/com/baeldung/concurrent/parameters/ParameterizedThreadExample.java

@@ -1,4 +1,4 @@
-package com.baeldung.concurrent.parameter;
+package com.baeldung.concurrent.parameters;
 
 import java.util.concurrent.Callable;
 import java.util.stream.IntStream;

core-java-modules/core-java-concurrency-advanced-2/src/test/java/com/baeldung/concurrent/parameters/ParameterizedThreadUnitTest.java

@@ -1,14 +1,13 @@
-package com.baeldung.parameters;
+package com.baeldung.concurrent.parameters;
 
-import com.baeldung.concurrent.parameter.AverageCalculator;
+import static org.junit.Assert.assertEquals;
-import org.junit.Test;
 
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 import java.util.stream.IntStream;
 
-import static org.junit.Assert.assertEquals;
+import org.junit.Test;
 
 public class ParameterizedThreadUnitTest {