fix conflicts

akka-modules/pom.xml

@@ -4,8 +4,8 @@
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <artifactId>akka-modules</artifactId>
-    <name>akka-modules</name>
     <packaging>pom</packaging>
+    <name>akka-modules</name>
 
     <parent>
         <artifactId>parent-modules</artifactId>

algorithms-modules/algorithms-miscellaneous-1/pom.xml

@@ -19,11 +19,6 @@
             <artifactId>commons-math3</artifactId>
             <version>${commons-math3.version}</version>
         </dependency>
-        <dependency>
-            <groupId>com.google.guava</groupId>
-            <artifactId>guava</artifactId>
-            <version>${guava.version}</version>
-        </dependency>
         <dependency>
             <groupId>commons-codec</groupId>
             <artifactId>commons-codec</artifactId>

algorithms-modules/algorithms-miscellaneous-5/pom.xml

@@ -29,11 +29,7 @@
             <artifactId>tradukisto</artifactId>
             <version>${tradukisto.version}</version>
         </dependency>
-        <dependency>
+
-            <groupId>com.google.guava</groupId>
-            <artifactId>guava</artifactId>
-            <version>${guava.version}</version>
-        </dependency>
         <!-- API, java.xml.bind module -->
         <dependency>
             <groupId>jakarta.xml.bind</groupId>

algorithms-modules/algorithms-miscellaneous-7/README.md

@@ -8,4 +8,10 @@
 - [Find Missing Number From a Given Array in Java](https://www.baeldung.com/java-array-find-missing-number)
 - [Calculate Weighted Mean in Java](https://www.baeldung.com/java-compute-weighted-average)
 - [Check if Two Strings Are Rotations of Each Other](https://www.baeldung.com/java-string-check-strings-rotations)
+- [Find the Largest Prime Under the Given Number in Java](https://www.baeldung.com/java-largest-prime-lower-threshold)
+- [Count the Number of Unique Digits in an Integer using Java](https://www.baeldung.com/java-int-count-unique-digits)
+- [Generate Juggler Sequence in Java](https://www.baeldung.com/java-generate-juggler-sequence)
+- [Finding the Parent of a Node in a Binary Search Tree with Java](https://www.baeldung.com/java-find-parent-node-binary-search-tree)
+- [Check if a Number Is a Happy Number in Java](https://www.baeldung.com/java-happy-sad-number-test)
+- [Find the Largest Number Possible After Removing k Digits of a Number](https://www.baeldung.com/java-find-largest-number-remove-k-digits)
 - More articles: [[<-- prev]](/algorithms-miscellaneous-6)

algorithms-modules/algorithms-miscellaneous-7/src/main/java/com/baeldung/algorithms/largestNumberRemovingK/LargestNumberRemoveKDigits.java

@@ -0,0 +1,57 @@
+package com.baeldung.algorithms.largestNumberRemovingK;
+
+import java.util.*;
+
+public class LargestNumberRemoveKDigits {
+    public static int findLargestNumberUsingArithmetic(int num, int k) {
+        for (int j = 0; j < k; j++) {
+
+            int result = 0;
+            int i = 1;
+
+            while (num / i > 0) {
+                int temp = (num / (i * 10))
+                        * i
+                        + (num % i);
+                i *= 10;
+
+                result = Math.max(result, temp);
+            }
+            num = result;
+        }
+
+        return num;
+    }
+
+    public static int findLargestNumberUsingStack(int num, int k) {
+        String numStr = Integer.toString(num);
+        int length = numStr.length();
+
+        if (k == length) return 0;
+
+        Stack<Character> stack = new Stack<>();
+
+        for (int i = 0; i < length; i++) {
+            char digit = numStr.charAt(i);
+
+            while (k > 0 && !stack.isEmpty() && stack.peek() < digit) {
+                stack.pop();
+                k--;
+            }
+
+            stack.push(digit);
+        }
+
+        while (k > 0) {
+            stack.pop();
+            k--;
+        }
+
+        StringBuilder result = new StringBuilder();
+        while (!stack.isEmpty()) {
+            result.insert(0, stack.pop());
+        }
+
+        return Integer.parseInt(result.toString());
+    }
+}

algorithms-modules/algorithms-miscellaneous-7/src/main/java/com/baeldung/algorithms/parentnodebinarytree/ParentKeeperTreeNode.java

@@ -0,0 +1,54 @@
+package com.baeldung.algorithms.parentnodebinarytree;
+
+import java.util.Objects;
+
+public class ParentKeeperTreeNode {
+
+    int value;
+    ParentKeeperTreeNode parent;
+    ParentKeeperTreeNode left;
+    ParentKeeperTreeNode right;
+
+    public ParentKeeperTreeNode(int value) {
+        this.value = value;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        ParentKeeperTreeNode treeNode = (ParentKeeperTreeNode) o;
+        return value == treeNode.value;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(value);
+    }
+
+    public void insert(int value) {
+        insert(this, value);
+    }
+
+    private void insert(ParentKeeperTreeNode currentNode, final int value) {
+        if (currentNode.left == null && value < currentNode.value) {
+            currentNode.left = new ParentKeeperTreeNode(value);
+            currentNode.left.parent = currentNode;
+            return;
+        }
+
+        if (currentNode.right == null && value > currentNode.value) {
+            currentNode.right = new ParentKeeperTreeNode(value);
+            currentNode.right.parent = currentNode;
+            return;
+        }
+
+        if (value > currentNode.value) {
+            insert(currentNode.right, value);
+        }
+
+        if (value < currentNode.value) {
+            insert(currentNode.left, value);
+        }
+    }
+}

algorithms-modules/algorithms-miscellaneous-7/src/main/java/com/baeldung/algorithms/parentnodebinarytree/TreeNode.java

@@ -0,0 +1,107 @@
+package com.baeldung.algorithms.parentnodebinarytree;
+
+import java.util.Deque;
+import java.util.LinkedList;
+import java.util.NoSuchElementException;
+import java.util.Objects;
+
+import static java.lang.String.format;
+
+public class TreeNode {
+    int value;
+    TreeNode left;
+    TreeNode right;
+
+    public TreeNode(int value) {
+        this.value = value;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        TreeNode treeNode = (TreeNode) o;
+        return value == treeNode.value;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(value);
+    }
+
+    public void insert(int value) {
+        insert(this, value);
+    }
+
+    private void insert(TreeNode currentNode, final int value) {
+        if (currentNode.left == null && value < currentNode.value) {
+            currentNode.left = new TreeNode(value);
+            return;
+        }
+
+        if (currentNode.right == null && value > currentNode.value) {
+            currentNode.right = new TreeNode(value);
+            return;
+        }
+
+        if (value > currentNode.value) {
+            insert(currentNode.right, value);
+        }
+
+        if (value < currentNode.value) {
+            insert(currentNode.left, value);
+        }
+    }
+
+    public TreeNode parent(int target) throws NoSuchElementException {
+        return parent(this, new TreeNode(target));
+    }
+
+    private TreeNode parent(TreeNode current, TreeNode target) throws NoSuchElementException {
+        if (target.equals(current) || current == null) {
+            throw new NoSuchElementException(format("No parent node found for 'target.value=%s' " +
+                            "The target is not in the tree or the target is the topmost root node.",
+                    target.value));
+        }
+
+        if (target.equals(current.left) || target.equals(current.right)) {
+            return current;
+        }
+
+        return parent(target.value < current.value ? current.left : current.right, target);
+    }
+
+    public TreeNode iterativeParent(int target) {
+        return iterativeParent(this, new TreeNode(target));
+    }
+
+    private TreeNode iterativeParent(TreeNode current, TreeNode target) {
+        Deque<TreeNode> parentCandidates = new LinkedList<>();
+
+        String notFoundMessage = format("No parent node found for 'target.value=%s' " +
+                        "The target is not in the tree or the target is the topmost root node.",
+                target.value);
+
+        if (target.equals(current)) {
+            throw new NoSuchElementException(notFoundMessage);
+        }
+
+        while (current != null || !parentCandidates.isEmpty()) {
+
+            while (current != null) {
+                parentCandidates.addFirst(current);
+                current = current.left;
+            }
+
+            current = parentCandidates.pollFirst();
+
+            if (target.equals(current.left) || target.equals(current.right)) {
+                return current;
+            }
+
+            current = current.right;
+        }
+
+        throw new NoSuchElementException(notFoundMessage);
+    }
+}

algorithms-modules/algorithms-miscellaneous-7/src/main/java/com/baeldung/algorithms/uniquedigit/UniqueDigitCounter.java

@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.uniquedigit;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class UniqueDigitCounter {
+
+    public static int countWithSet(int number) {
+        number = Math.abs(number);
+        Set<Character> uniqueDigits = new HashSet<>();
+        String numberStr = String.valueOf(number);
+        for (char digit : numberStr.toCharArray()) {
+            uniqueDigits.add(digit);
+        }
+        return uniqueDigits.size();
+    }
+
+    public static int countWithBitManipulation(int number) {
+        if (number == 0) {
+            return 1;
+        }
+        number = Math.abs(number);
+        int mask = 0;
+        while (number > 0) {
+            int digit = number % 10;
+            mask |= 1 << digit;
+            number /= 10;
+        }
+        return Integer.bitCount(mask);
+    }
+
+    public static long countWithStreamApi(int number) {
+        return String.valueOf(Math.abs(number)).chars().distinct().count();
+    }
+
+}

algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/happynumber/HappyNumberUnitTest.java

@@ -0,0 +1,82 @@
+package com.baeldung.algorithms.happynumber;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.junit.jupiter.api.Test;
+
+class HappyNumberDecider {
+
+    public static boolean isHappyNumber(int n) {
+        Set<Integer> checkedNumbers = new HashSet<>();
+        while (true) {
+            n = sumDigitsSquare(n);
+            if (n == 1) {
+                return true;
+            }
+            if (checkedNumbers.contains(n)) {
+                return false;
+            }
+            checkedNumbers.add(n);
+        }
+    }
+
+    public static boolean isHappyNumberFloyd(int n) {
+        int slow = n;
+        int fast = n;
+        do {
+            slow = sumDigitsSquare(slow);
+            fast = sumDigitsSquare(sumDigitsSquare(fast));
+        } while (slow != fast);
+
+        return slow == 1;
+    }
+
+    private static int sumDigitsSquare(int n) {
+        int squareSum = 0;
+        while (n != 0) {
+            squareSum += (n % 10) * (n % 10);
+            n /= 10;
+        }
+        return squareSum;
+    }
+}
+
+public class HappyNumberUnitTest {
+
+    @Test
+    void whenUsingIsHappyNumber_thenGetTheExpectedResult() {
+        assertTrue(HappyNumberDecider.isHappyNumber(7));
+        assertTrue(HappyNumberDecider.isHappyNumber(10));
+        assertTrue(HappyNumberDecider.isHappyNumber(13));
+        assertTrue(HappyNumberDecider.isHappyNumber(19));
+        assertTrue(HappyNumberDecider.isHappyNumber(23));
+
+        assertFalse(HappyNumberDecider.isHappyNumber(4));
+        assertFalse(HappyNumberDecider.isHappyNumber(6));
+        assertFalse(HappyNumberDecider.isHappyNumber(11));
+        assertFalse(HappyNumberDecider.isHappyNumber(15));
+        assertFalse(HappyNumberDecider.isHappyNumber(20));
+
+    }
+
+    @Test
+    void whenUsingIsHappyNumber2_thenGetTheExpectedResult() {
+        assertTrue(HappyNumberDecider.isHappyNumberFloyd(7));
+        assertTrue(HappyNumberDecider.isHappyNumberFloyd(10));
+        assertTrue(HappyNumberDecider.isHappyNumberFloyd(13));
+        assertTrue(HappyNumberDecider.isHappyNumberFloyd(19));
+        assertTrue(HappyNumberDecider.isHappyNumberFloyd(23));
+
+        assertFalse(HappyNumberDecider.isHappyNumberFloyd(4));
+        assertFalse(HappyNumberDecider.isHappyNumberFloyd(6));
+        assertFalse(HappyNumberDecider.isHappyNumberFloyd(11));
+        assertFalse(HappyNumberDecider.isHappyNumberFloyd(15));
+        assertFalse(HappyNumberDecider.isHappyNumberFloyd(20));
+
+    }
+
+}

algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/largestNumberRemovingK/LargestNumberRemoveKDigitsUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.algorithms.largestNumberRemovingK;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class LargestNumberRemoveKDigitsUnitTest {
+
+    @Test
+    public void givenNumber_UsingArithmeticRemoveKDigits_thenReturnLargestNumber(){
+        Assertions.assertEquals(LargestNumberRemoveKDigits.findLargestNumberUsingArithmetic(9461, 1), 961);
+        Assertions.assertEquals(LargestNumberRemoveKDigits.findLargestNumberUsingArithmetic(463, 2), 6);
+        Assertions.assertEquals(LargestNumberRemoveKDigits.findLargestNumberUsingArithmetic(98625410, 6), 98);
+        Assertions.assertEquals(LargestNumberRemoveKDigits.findLargestNumberUsingArithmetic(20, 2), 0);
+        Assertions.assertEquals(LargestNumberRemoveKDigits.findLargestNumberUsingArithmetic(98989, 4), 9);
+    }
+
+    @Test
+    public void givenNumber_UsingStackRemoveKDigits_thenReturnLargestNumber(){
+        Assertions.assertEquals(LargestNumberRemoveKDigits.findLargestNumberUsingStack(9461, 1), 961);
+        Assertions.assertEquals(LargestNumberRemoveKDigits.findLargestNumberUsingStack(463, 2), 6);
+        Assertions.assertEquals(LargestNumberRemoveKDigits.findLargestNumberUsingStack(98625410, 6), 98);
+        Assertions.assertEquals(LargestNumberRemoveKDigits.findLargestNumberUsingStack(20, 2), 0);
+        Assertions.assertEquals(LargestNumberRemoveKDigits.findLargestNumberUsingStack(98989, 4), 9);
+    }
+}

algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/parentnodebinarytree/BinaryTreeParentNodeFinderUnitTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.algorithms.parentnodebinarytree;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.NoSuchElementException;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class BinaryTreeParentNodeFinderUnitTest {
+
+    private TreeNode subject;
+
+    @BeforeEach
+    void setUp() {
+        subject = new TreeNode(8);
+        subject.insert(5);
+        subject.insert(12);
+        subject.insert(3);
+        subject.insert(7);
+        subject.insert(1);
+        subject.insert(4);
+        subject.insert(11);
+        subject.insert(14);
+        subject.insert(13);
+        subject.insert(16);
+    }
+
+    @Test
+    void givenBinaryTree_whenFindParentNode_thenReturnCorrectParentNode() {
+        assertEquals(8, subject.parent(5).value);
+        assertEquals(5, subject.parent(3).value);
+        assertEquals(5, subject.parent(7).value);
+        assertEquals(3, subject.parent(4).value);
+        assertEquals(3, subject.parent(1).value);
+        assertEquals(8, subject.parent(12).value);
+        assertEquals(12, subject.parent(14).value);
+        assertEquals(12, subject.parent(11).value);
+        assertEquals(14, subject.parent(16).value);
+        assertEquals(14, subject.parent(13).value);
+        assertThrows(NoSuchElementException.class, () -> subject.parent(1231));
+        assertThrows(NoSuchElementException.class, () -> subject.parent(8));
+    }
+
+    @Test
+    void givenBinaryTree_whenFindParentNodeIteratively_thenReturnCorrectParentNode() {
+        assertEquals(8, subject.iterativeParent(5).value);
+        assertEquals(5, subject.iterativeParent(3).value);
+        assertEquals(5, subject.iterativeParent(7).value);
+        assertEquals(3, subject.iterativeParent(4).value);
+        assertEquals(3, subject.iterativeParent(1).value);
+        assertEquals(8, subject.iterativeParent(12).value);
+        assertEquals(12, subject.iterativeParent(14).value);
+        assertEquals(12, subject.iterativeParent(11).value);
+        assertEquals(14, subject.iterativeParent(16).value);
+        assertEquals(14, subject.iterativeParent(13).value);
+        assertThrows(NoSuchElementException.class, () -> subject.iterativeParent(1231));
+        assertThrows(NoSuchElementException.class, () -> subject.iterativeParent(8));
+    }
+
+    @Test
+    void givenParentKeeperBinaryTree_whenGetParent_thenReturnCorrectParent() {
+        ParentKeeperTreeNode subject = new ParentKeeperTreeNode(8);
+        subject.insert(5);
+        subject.insert(12);
+        subject.insert(3);
+        subject.insert(7);
+        subject.insert(1);
+        subject.insert(4);
+        subject.insert(11);
+        subject.insert(14);
+        subject.insert(13);
+        subject.insert(16);
+
+        assertNull(subject.parent);
+        assertEquals(8, subject.left.parent.value);
+        assertEquals(8, subject.right.parent.value);
+        assertEquals(5, subject.left.left.parent.value);
+        assertEquals(5, subject.left.right.parent.value);
+
+        // tests for other nodes
+    }
+}

algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/uniquedigit/UniqueDigitCounterUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.algorithms.uniquedigit;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class UniqueDigitCounterUnitTest {
+
+    @Test
+    public void givenNotNegativeNumber_whenCountUniqueDigits_thenCorrectCount() {
+        assertEquals(3, UniqueDigitCounter.countWithSet(122333));
+        assertEquals(1, UniqueDigitCounter.countWithSet(0));
+        assertEquals(2, UniqueDigitCounter.countWithSet(101));
+
+        assertEquals(3, UniqueDigitCounter.countWithBitManipulation(122333));
+        assertEquals(1, UniqueDigitCounter.countWithBitManipulation(0));
+        assertEquals(2, UniqueDigitCounter.countWithBitManipulation(101));
+
+        assertEquals(3, UniqueDigitCounter.countWithStreamApi(122333));
+        assertEquals(1, UniqueDigitCounter.countWithStreamApi(0));
+        assertEquals(2, UniqueDigitCounter.countWithStreamApi(101));
+    }
+
+    @Test
+    public void givenNegativeNumber_whenCountUniqueDigits_thenCorrectCount() {
+        assertEquals(3, UniqueDigitCounter.countWithSet(-122333));
+        assertEquals(3, UniqueDigitCounter.countWithBitManipulation(-122333));
+        assertEquals(3, UniqueDigitCounter.countWithStreamApi(-122333));
+    }
+
+    @Test
+    public void givenLargeNumber_whenCountUniqueDigits_thenCorrectCount() {
+        assertEquals(2, UniqueDigitCounter.countWithSet(1000000000));
+        assertEquals(2, UniqueDigitCounter.countWithBitManipulation(1000000000));
+        assertEquals(2, UniqueDigitCounter.countWithStreamApi(1000000000));
+    }
+
+}

algorithms-modules/algorithms-miscellaneous-8/README.md

@@ -0,0 +1,2 @@
+### Relevant Articles: 
+- [Vigenère Cipher in Java](https://www.baeldung.com/java-vigenere-cipher)

algorithms-modules/algorithms-miscellaneous-8/pom.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>algorithms-miscellaneous-8</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>algorithms-miscellaneous-8</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>algorithms-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+</project>

algorithms-modules/algorithms-miscellaneous-8/src/main/java/com/baeldung/algorithms/mergeintervals/Interval.java

@@ -0,0 +1,37 @@
+package com.baeldung.algorithms.mergeintervals;
+
+import java.util.Objects;
+
+public class Interval {
+    int start;
+    int end;
+
+    Interval(int start, int end) {
+        this.start = start;
+        this.end = end;
+    }
+
+    public void setEnd(int end) {
+        this.end = end;
+    }
+
+    @Override
+    public String toString() {
+        return "Interval{" + "start=" + start + ", end=" + end + '}';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        Interval interval = (Interval) o;
+        return start == interval.start && end == interval.end;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(start, end);
+    }
+}

algorithms-modules/algorithms-miscellaneous-8/src/main/java/com/baeldung/algorithms/mergeintervals/MergeOverlappingIntervals.java

@@ -0,0 +1,29 @@
+package com.baeldung.algorithms.mergeintervals;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class MergeOverlappingIntervals {
+
+    public List<Interval> doMerge(List<Interval> intervals) {
+        // Sort the intervals based on start time
+        intervals.sort((one, two) -> one.start - two.start);
+
+        // Create somewhere to put the merged list, start it off with the earliest starting interval
+        ArrayList<Interval> merged = new ArrayList<>();
+        merged.add(intervals.get(0));
+
+        // Loop over each interval and merge if start time is before the end time of the
+        // previous interval
+        intervals.forEach(interval -> {
+            if (merged.get(merged.size() - 1).end > interval.start) {
+                merged.get(merged.size() - 1).setEnd(interval.end);
+            } else {
+                merged.add(interval);
+            }
+        });
+
+        return merged;
+    }
+
+}

algorithms-modules/algorithms-miscellaneous-8/src/test/java/com/baeldung/algorithms/mergeintervals/MergeIntervalsUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.algorithms.mergeintervals;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+
+import org.junit.jupiter.api.Test;
+
+class MergeIntervalsUnitTest {
+
+    private ArrayList<Interval> intervals = new ArrayList<>(Arrays.asList(
+      new Interval(2, 5),
+      new Interval(13, 20),
+      new Interval(11, 15),
+      new Interval(1, 3)
+    ));
+    private ArrayList<Interval> intervalsMerged = new ArrayList<>(Arrays.asList(
+      new Interval(1, 5),
+      new Interval(11, 20)
+    ));
+
+    @Test
+    void givenIntervals_whenMerging_thenReturnMergedIntervals() {
+        MergeOverlappingIntervals merger = new MergeOverlappingIntervals();
+        ArrayList<Interval> result = (ArrayList<Interval>) merger.doMerge(intervals);
+        assertArrayEquals(intervalsMerged.toArray(), result.toArray());
+    }
+
+}

algorithms-modules/algorithms-miscellaneous-8/src/test/java/com/baeldung/algorithms/vigenere/VigenereCipher.java

@@ -0,0 +1,69 @@
+package com.baeldung.algorithms.vigenere;
+
+public class VigenereCipher {
+    private final String characters;
+
+    public VigenereCipher() {
+        this("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
+    }
+
+    public VigenereCipher(String characters) {
+        this.characters = characters;
+    }
+
+    public String encode(String input, String key) {
+        String result = "";
+
+        int keyPosition = 0;
+        for (char c : input.toCharArray()) {
+            char k = key.charAt(keyPosition % key.length());
+
+            int charIndex = characters.indexOf(c);
+            int keyIndex = characters.indexOf(k);
+
+            if (charIndex >= 0) {
+                if (keyIndex >= 0) {
+                    int newCharIndex = (charIndex + keyIndex + 1) % characters.length();
+                    c = characters.charAt(newCharIndex);
+
+                }
+
+                keyPosition++;
+            }
+
+            result += c;
+        }
+
+        return result;
+    }
+
+    public String decode(String input, String key) {
+        String result = "";
+
+        int keyPosition = 0;
+        for (char c : input.toCharArray()) {
+            char k = key.charAt(keyPosition % key.length());
+
+            int charIndex = characters.indexOf(c);
+            int keyIndex = characters.indexOf(k);
+
+            if (charIndex >= 0) {
+                if (keyIndex >= 0) {
+                    int newCharIndex = charIndex - keyIndex - 1;
+                    if (newCharIndex < 0) {
+                        newCharIndex = characters.length() + newCharIndex;
+                    }
+                    c = characters.charAt(newCharIndex);
+
+                }
+
+                keyPosition++;
+            }
+
+            result += c;
+        }
+
+        return result;
+    }
+
+}

algorithms-modules/algorithms-miscellaneous-8/src/test/java/com/baeldung/algorithms/vigenere/VigenereCipherUnitTest.java

@@ -0,0 +1,76 @@
+package com.baeldung.algorithms.vigenere;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class VigenereCipherUnitTest {
+
+    @Test
+    void encodeBaeldung() {
+        VigenereCipher cipher = new VigenereCipher();
+        String output = cipher.encode("BAELDUNG", "HELLO");
+
+        Assertions.assertEquals("JFQXSCSS", output);
+    }
+
+    @Test
+    void encodeBaeldungMixedCharacters() {
+        VigenereCipher cipher = new VigenereCipher("JQFVHPWORZSLNMKYCGBUXIEDTA");
+        String output = cipher.encode("BAELDUNG", "HELLO");
+
+        Assertions.assertEquals("DERDPTZV", output);
+    }
+
+    @Test
+    void encodeArticleTitle() {
+        VigenereCipher cipher = new VigenereCipher();
+        String output = cipher.encode("VIGENERE CIPHER IN JAVA", "BAELDUNG");
+
+        Assertions.assertEquals("XJLQRZFL EJUTIM WU LBAM", output);
+    }
+
+    @Test
+    void encodeArticleTitleMoreCharacters() {
+        VigenereCipher cipher = new VigenereCipher("ABCDEFGHIJKLMNOPQRSTUVWXYZ ");
+        String output = cipher.encode("VIGENERE CIPHER IN JAVA", "BAELDUNG");
+
+        Assertions.assertEquals("XJLQRZELBDNALZEGKOEVEPO", output);
+    }
+
+    @Test
+    void decodeBaeldung() {
+        VigenereCipher cipher = new VigenereCipher();
+        String output = cipher.decode("JFQXSCSS", "HELLO");
+
+        Assertions.assertEquals("BAELDUNG", output);
+    }
+
+    @Test
+    void decodeBaeldungMixedCharacters() {
+        VigenereCipher cipher = new VigenereCipher("JQFVHPWORZSLNMKYCGBUXIEDTA");
+        String output = cipher.decode("DERDPTZV", "HELLO");
+
+        Assertions.assertEquals("BAELDUNG", output);
+    }
+
+    @Test
+    void decodeArticleTitleMoreCharacters() {
+        VigenereCipher cipher = new VigenereCipher("ABCDEFGHIJKLMNOPQRSTUVWXYZ ");
+        String output = cipher.decode("XJLQRZELBDNALZEGKOEVEPO", "BAELDUNG");
+
+        Assertions.assertEquals("VIGENERE CIPHER IN JAVA", output);
+    }
+
+    @Test
+    void encodeDecodeBaeldung() {
+        VigenereCipher cipher = new VigenereCipher();
+
+        String input = "BAELDUNG";
+        String key = "HELLO";
+
+        String encoded = cipher.encode(input, key);
+        String decoded = cipher.decode(encoded, key);
+
+        Assertions.assertEquals(input, decoded);
+    }
+}

algorithms-modules/pom.xml

@@ -22,6 +22,7 @@
         <module>algorithms-miscellaneous-5</module>
         <module>algorithms-miscellaneous-6</module>
         <module>algorithms-miscellaneous-7</module>
+        <module>algorithms-miscellaneous-8</module>
         <module>algorithms-searching</module>
         <module>algorithms-sorting</module>
         <module>algorithms-sorting-2</module>

apache-cxf-modules/cxf-spring/pom.xml

@@ -4,8 +4,8 @@
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <artifactId>cxf-spring</artifactId>
-    <name>cxf-spring</name>
     <packaging>war</packaging>
+    <name>cxf-spring</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

apache-cxf-modules/pom.xml

@@ -5,8 +5,9 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>apache-cxf-modules</artifactId>
     <version>0.0.1-SNAPSHOT</version>
-    <name>apache-cxf-modules</name>
     <packaging>pom</packaging>
+    <name>apache-cxf-modules</name>
+
 
     <parent>
         <groupId>com.baeldung</groupId>

apache-cxf-modules/sse-jaxrs/pom.xml

@@ -4,8 +4,8 @@
     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>sse-jaxrs</artifactId>
-    <name>sse-jaxrs</name>
     <packaging>pom</packaging>
+    <name>sse-jaxrs</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

apache-cxf-modules/sse-jaxrs/sse-jaxrs-server/pom.xml

@@ -4,8 +4,8 @@
     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>sse-jaxrs-server</artifactId>
-    <name>sse-jaxrs-server</name>
     <packaging>war</packaging>
+    <name>sse-jaxrs-server</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

apache-httpclient4/pom.xml

@@ -5,8 +5,8 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>apache-httpclient4</artifactId>
     <version>0.1-SNAPSHOT</version>
-    <name>apache-httpclient4</name>
     <packaging>war</packaging>
+    <name>apache-httpclient4</name>
 
     <parent>
         <groupId>com.baeldung</groupId>
@@ -82,7 +82,7 @@
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-oxm</artifactId>
-            <version>${spring.version}</version>
+            <version>${spring-oxm.version}</version>
         </dependency>
         <!-- marshalling -->
         <dependency>
@@ -176,12 +176,6 @@
             <version>${jstl.version}</version>
             <scope>runtime</scope>
         </dependency>
-        <!-- util -->
-        <dependency>
-            <groupId>com.google.guava</groupId>
-            <artifactId>guava</artifactId>
-            <version>${guava.version}</version>
-        </dependency>
         <!-- test scoped -->
         <dependency>
             <groupId>org.springframework</groupId>
@@ -199,7 +193,6 @@
                 <filtering>true</filtering>
             </resource>
         </resources>
-
     </build>
 
     <profiles>
@@ -233,6 +226,7 @@
     </profiles>
 
     <properties>
+        <spring-oxm.version>6.1.4</spring-oxm.version>
         <!-- util -->
         <commons-codec.version>1.16.0</commons-codec.version>
         <httpasyncclient.version>4.1.5</httpasyncclient.version>

apache-kafka-2/README.md

@@ -16,3 +16,4 @@ You can build the project from the command line using: *mvn clean install*, or i
 - [Introduction to Apache Kafka](https://www.baeldung.com/apache-kafka)
 - [Ensuring Message Ordering in Kafka: Strategies and Configurations](https://www.baeldung.com/kafka-message-ordering)
 - [Read Multiple Messages with Apache Kafka](https://www.baeldung.com/kafka-read-multiple-messages)
+- [Creating a Kafka Listener Using the Consumer API](https://www.baeldung.com/kafka-create-listener-consumer-api)

apache-kafka-3/README.md

@@ -0,0 +1,10 @@
+## Apache Kafka
+
+This module contains articles about Apache Kafka.
+
+##### Building the project
+You can build the project from the command line using: *mvn clean install*, or in an IDE.
+
+### Relevant Articles:
+- [Commit Offsets in Kafka](https://www.baeldung.com/kafka-commit-offsets)
+

apache-kafka-3/pom.xml

@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>apache-kafka-3</artifactId>
+    <name>apache-kafka-3</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.kafka</groupId>
+            <artifactId>kafka-clients</artifactId>
+            <version>${kafka.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-api</artifactId>
+            <version>${org.slf4j.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+            <version>${jackson.databind.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <kafka.version>3.6.1</kafka.version>
+        <jackson.databind.version>2.15.2</jackson.databind.version>
+    </properties>
+    <profiles>
+        <profile>
+            <id>integration-jdk9-and-above</id>
+        </profile>
+    </profiles>
+</project>

apache-kafka-3/src/main/java/com/baeldung/kafka/commitoffset/AsyncCommit.java

@@ -0,0 +1,23 @@
+package com.baeldung.kafka.commitoffset;
+
+import com.baeldung.kafka.commitoffset.config.KafkaConfigProperties;
+
+import java.time.Duration;
+
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.clients.consumer.ConsumerRecords;
+import org.apache.kafka.clients.consumer.KafkaConsumer;
+
+public class AsyncCommit {
+
+    public static void main(String[] args) {
+
+        KafkaConsumer<Long, String> consumer = new KafkaConsumer<>(KafkaConfigProperties.getProperties());
+        consumer.subscribe(KafkaConfigProperties.getTopic());
+        ConsumerRecords<Long, String> messages = consumer.poll(Duration.ofSeconds(10));
+        for (ConsumerRecord<Long, String> message : messages) {
+            // processed message
+            consumer.commitAsync();
+        }
+    }
+}

apache-kafka-3/src/main/java/com/baeldung/kafka/commitoffset/AutomaticCommit.java

@@ -0,0 +1,26 @@
+package com.baeldung.kafka.commitoffset;
+
+import com.baeldung.kafka.commitoffset.config.KafkaConfigProperties;
+
+import java.time.Duration;
+import java.util.Properties;
+
+import org.apache.kafka.clients.consumer.ConsumerConfig;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.clients.consumer.ConsumerRecords;
+import org.apache.kafka.clients.consumer.KafkaConsumer;
+
+public class AutomaticCommit {
+
+    public static void main(String[] args) {
+
+        Properties properties = KafkaConfigProperties.getProperties();
+        properties.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, "true");
+        KafkaConsumer<Long, String> consumer = new KafkaConsumer<>(properties);
+        consumer.subscribe(KafkaConfigProperties.getTopic());
+        ConsumerRecords<Long, String> messages = consumer.poll(Duration.ofSeconds(10));
+        for (ConsumerRecord<Long, String> message : messages) {
+            // processed message
+        }
+    }
+}

apache-kafka-3/src/main/java/com/baeldung/kafka/commitoffset/SpecificOffsetCommit.java

@@ -0,0 +1,34 @@
+package com.baeldung.kafka.commitoffset;
+
+import com.baeldung.kafka.commitoffset.config.KafkaConfigProperties;
+
+import java.time.Duration;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.clients.consumer.ConsumerRecords;
+import org.apache.kafka.clients.consumer.KafkaConsumer;
+import org.apache.kafka.clients.consumer.OffsetAndMetadata;
+import org.apache.kafka.common.TopicPartition;
+
+public class SpecificOffsetCommit {
+    public static void main(String[] args) {
+
+        KafkaConsumer<Long, String> consumer = new KafkaConsumer<>(KafkaConfigProperties.getProperties());
+        consumer.subscribe(KafkaConfigProperties.getTopic());
+        Map<TopicPartition, OffsetAndMetadata> currentOffsets = new HashMap<>();
+        int messageProcessed = 0;
+        while (true) {
+            ConsumerRecords<Long, String> messages = consumer.poll(Duration.ofSeconds(10));
+            for (ConsumerRecord<Long, String> message : messages) {
+                // processed message
+                messageProcessed++;
+                currentOffsets.put(new TopicPartition(message.topic(), message.partition()), new OffsetAndMetadata(message.offset() + 1));
+                if (messageProcessed % 50 == 0) {
+                    consumer.commitSync(currentOffsets);
+                }
+            }
+        }
+    }
+}

apache-kafka-3/src/main/java/com/baeldung/kafka/commitoffset/SyncCommit.java

@@ -0,0 +1,23 @@
+package com.baeldung.kafka.commitoffset;
+
+import com.baeldung.kafka.commitoffset.config.KafkaConfigProperties;
+
+import java.time.Duration;
+
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.clients.consumer.ConsumerRecords;
+import org.apache.kafka.clients.consumer.KafkaConsumer;
+
+public class SyncCommit {
+
+    public static void main(String[] args) {
+
+        KafkaConsumer<Long, String> consumer = new KafkaConsumer<>(KafkaConfigProperties.getProperties());
+        consumer.subscribe(KafkaConfigProperties.getTopic());
+        ConsumerRecords<Long, String> messages = consumer.poll(Duration.ofSeconds(10));
+        for (ConsumerRecord<Long, String> message : messages) {
+            // processed message
+            consumer.commitSync();
+        }
+    }
+}

apache-kafka-3/src/main/java/com/baeldung/kafka/commitoffset/config/KafkaConfigProperties.java

@@ -0,0 +1,31 @@
+package com.baeldung.kafka.commitoffset.config;
+
+import java.util.ArrayList;
+import java.util.Properties;
+
+import org.apache.kafka.clients.consumer.ConsumerConfig;
+import org.apache.kafka.common.serialization.StringDeserializer;
+
+/**
+ * @author amitkumar
+ */
+public class KafkaConfigProperties {
+    public static final String MY_TOPIC = "my-topic";
+
+    public static Properties getProperties() {
+
+        Properties props = new Properties();
+        props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, "false");
+        props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
+        props.put(ConsumerConfig.GROUP_ID_CONFIG, "MyFirstConsumer");
+        props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
+        props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
+        return props;
+    }
+
+    public static ArrayList<String> getTopic() {
+        ArrayList<String> topics = new ArrayList<>();
+        topics.add(MY_TOPIC);
+        return topics;
+    }
+}

apache-kafka-3/src/test/resources/logback.xml

@@ -0,0 +1,11 @@
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

apache-kafka/pom.xml

@@ -71,11 +71,6 @@
             <version>${flink.version}</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>com.google.guava</groupId>
-            <artifactId>guava</artifactId>
-            <version>${guava.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.awaitility</groupId>
             <artifactId>awaitility</artifactId>

apache-libraries-2/README.md

@@ -1,3 +1,5 @@
 ## Relevant Articles
 - [Understanding XSLT Processing in Java](https://www.baeldung.com/java-extensible-stylesheet-language-transformations)
 - [Add Camel Route at Runtime in Java](https://www.baeldung.com/java-camel-dynamic-route)
+
+- More articles: [[<-- prev]](../apache-libraries)

apache-libraries-2/pom.xml

@@ -24,14 +24,12 @@
             <artifactId>camel-core</artifactId>
             <version>${camel.version}</version>
         </dependency>
-
         <dependency>
             <groupId>org.apache.camel</groupId>
             <artifactId>camel-test-junit5</artifactId>
             <version>${camel.version}</version>
             <scope>test</scope>
         </dependency>
-
         <dependency>
             <groupId>org.apache.camel</groupId>
             <artifactId>camel-main</artifactId>

apache-libraries/README.md

@@ -13,3 +13,5 @@ This module contains articles about various Apache libraries and utilities
 - [Introduction to Apache Curator](https://www.baeldung.com/apache-curator)
 - [A Quick Guide to Apache Geode](https://www.baeldung.com/apache-geode)
 - [Guide To Solr in Java With Apache SolrJ](https://www.baeldung.com/apache-solrj)
+
+- More articles: [[next -->]](../apache-libraries-2)

apache-spark/pom.xml

@@ -5,8 +5,8 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>apache-spark</artifactId>
     <version>1.0-SNAPSHOT</version>
-    <name>apache-spark</name>
     <packaging>jar</packaging>
+    <name>apache-spark</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

apache-thrift/pom.xml

@@ -5,8 +5,8 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>apache-thrift</artifactId>
     <version>0.0.1-SNAPSHOT</version>
-    <name>apache-thrift</name>
     <packaging>pom</packaging>
+    <name>apache-thrift</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

apache-velocity/pom.xml

@@ -5,8 +5,8 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>apache-velocity</artifactId>
     <version>0.1-SNAPSHOT</version>
-    <name>apache-velocity</name>
     <packaging>war</packaging>
+    <name>apache-velocity</name>
 
     <parent>
         <groupId>com.baeldung</groupId>
@@ -28,7 +28,7 @@
         <dependency>
             <groupId>org.apache.httpcomponents</groupId>
             <artifactId>httpclient</artifactId>
-            <version>${org.apache.httpcomponents.version}</version>
+            <version>${httpclient.version}</version>
             <scope>test</scope>
             <exclusions>
                 <exclusion>
@@ -60,7 +60,7 @@
     </build>
 
     <properties>
-        <org.apache.httpcomponents.version>4.5.2</org.apache.httpcomponents.version>
+        <httpclient.version>4.5.2</httpclient.version>
         <velocity-version>1.7</velocity-version>
         <velocity-tools-version>2.0</velocity-tools-version>
     </properties>

aws-modules/aws-dynamodb/pom.xml

@@ -5,8 +5,8 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>aws-dynamodb</artifactId>
     <version>0.1.0-SNAPSHOT</version>
-    <name>aws-dynamodb</name>
     <packaging>jar</packaging>
+    <name>aws-dynamodb</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

aws-modules/aws-lambda-modules/lambda-function/pom.xml

@@ -4,8 +4,8 @@
     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>lambda-function</artifactId>
-    <version>0.1.0-SNAPSHOT</version>
     <name>lambda-function</name>
+    <version>0.1.0-SNAPSHOT</version>
     <packaging>jar</packaging>
 
     <parent>

aws-modules/aws-lambda-modules/pom.xml

@@ -4,8 +4,8 @@
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <artifactId>aws-lambda-modules</artifactId>
-    <name>aws-lambda-modules</name>
     <packaging>pom</packaging>
+    <name>aws-lambda-modules</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

aws-modules/aws-lambda-modules/shipping-tracker-lambda/ShippingFunction/pom.xml

@@ -3,8 +3,8 @@
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <artifactId>ShippingFunction</artifactId>
-    <version>1.0</version>
     <name>ShippingFunction</name>
+    <version>1.0</version>
     <packaging>jar</packaging>
 
     <parent>

aws-modules/aws-lambda-modules/todo-reminder-lambda/ToDoFunction/pom.xml

@@ -4,8 +4,8 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>helloworld</groupId>
     <artifactId>ToDoFunction</artifactId>
-    <version>1.0</version>
     <name>ToDoFunction</name>
+    <version>1.0</version>
     <packaging>jar</packaging>
 
     <parent>

aws-modules/aws-miscellaneous/pom.xml

@@ -5,8 +5,8 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>aws-miscellaneous</artifactId>
     <version>0.1.0-SNAPSHOT</version>
-    <name>aws-miscellaneous</name>
     <packaging>jar</packaging>
+    <name>aws-miscellaneous</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

aws-modules/aws-reactive/pom.xml

@@ -87,6 +87,7 @@
             <plugin>
                 <groupId>org.springframework.boot</groupId>
                 <artifactId>spring-boot-maven-plugin</artifactId>
+                <version>${spring.version}</version>
             </plugin>
         </plugins>
     </build>

aws-modules/aws-s3/README.md

@@ -12,3 +12,4 @@ This module contains articles about Simple Storage Service (S3) on AWS
 - [Update an Existing Amazon S3 Object Using Java](https://www.baeldung.com/java-update-amazon-s3-object)
 - [How To Rename Files and Folders in Amazon S3](https://www.baeldung.com/java-amazon-s3-rename-files-folders)
 - [Update an Existing Amazon S3 Object Using Java](https://www.baeldung.com/java-update-amazon-s3-object)
+- [How to Mock Amazon S3 for Integration Test](https://www.baeldung.com/java-amazon-simple-storage-service-mock-testing)

aws-modules/aws-s3/pom.xml

@@ -5,8 +5,8 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>aws-s3</artifactId>
     <version>0.1.0-SNAPSHOT</version>
-    <name>aws-s3</name>
     <packaging>jar</packaging>
+    <name>aws-s3</name>
 
     <parent>
         <groupId>com.baeldung</groupId>
@@ -26,7 +26,6 @@
             <version>${aws.java.sdk.version}</version>
             <scope>test</scope>
         </dependency>
-
         <dependency>
             <groupId>commons-io</groupId>
             <artifactId>commons-io</artifactId>
@@ -56,7 +55,6 @@
             <version>${com.adobe.testing.version}</version>
             <scope>test</scope>
         </dependency>
-
         <dependency>
             <groupId>org.testcontainers</groupId>
             <artifactId>junit-jupiter</artifactId>

aws-modules/aws-s3/src/test/java/com/baeldung/s3/S3CrudServiceLiveTest.java

@@ -21,7 +21,7 @@ import software.amazon.awssdk.utils.AttributeMap;
 // This live test needs a running Docker instance so that a S3Mock Container can be started
 
 @Testcontainers
-public class S3CrudServiceIntegrationTest {
+public class S3CrudServiceLiveTest {
 
     private static final String TEST_BUCKET_NAME = "test-bucket";
 

aws-modules/pom.xml

@@ -4,6 +4,7 @@
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <artifactId>aws-modules</artifactId>
+    <packaging>pom</packaging>
     <name>aws-modules</name>
 
     <parent>
@@ -12,16 +13,6 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
 
-    <dependencies>
-        <dependency>
-            <groupId>com.amazonaws</groupId>
-            <artifactId>aws-java-sdk-dynamodb</artifactId>
-            <version>1.12.523</version>
-            <scope>compile</scope>
-        </dependency>
-    </dependencies>
-    <packaging>pom</packaging>
-
     <modules>
         <module>aws-app-sync</module>
         <module>aws-dynamodb</module>
@@ -31,6 +22,15 @@
         <module>aws-s3</module>
     </modules>
 
+    <dependencies>
+        <dependency>
+            <groupId>com.amazonaws</groupId>
+            <artifactId>aws-java-sdk-dynamodb</artifactId>
+            <version>1.12.523</version>
+            <scope>compile</scope>
+        </dependency>
+    </dependencies>
+
     <properties>
         <aws-java-sdk.version>1.12.331</aws-java-sdk.version>
         <aws-java-sdk-v2.version>2.24.9</aws-java-sdk-v2.version>

azure/pom.xml

@@ -5,8 +5,8 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>azure</artifactId>
     <version>0.1</version>
-    <name>azure</name>
     <packaging>war</packaging>
+    <name>azure</name>
     <description>Demo project for Spring Boot on Azure</description>
 
     <parent>

checker-framework/pom.xml

@@ -5,8 +5,8 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>checker-framework</artifactId>
     <version>1.0-SNAPSHOT</version>
-    <name>checker-framework</name>
     <packaging>jar</packaging>
+    <name>checker-framework</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

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

@@ -4,8 +4,8 @@
     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-10</artifactId>
-    <name>core-java-10</name>
     <packaging>jar</packaging>
+    <name>core-java-10</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

core-java-modules/core-java-11-2/pom.xml

@@ -4,8 +4,8 @@
     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-11-2</artifactId>
-    <name>core-java-11-2</name>
     <packaging>jar</packaging>
+    <name>core-java-11-2</name>
 
     <parent>
         <groupId>com.baeldung</groupId>
@@ -15,11 +15,6 @@
     </parent>
 
     <dependencies>
-        <dependency>
-            <groupId>com.google.guava</groupId>
-            <artifactId>guava</artifactId>
-            <version>${guava.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.mock-server</groupId>
             <artifactId>mockserver-junit-jupiter</artifactId>

core-java-modules/core-java-11-3/pom.xml

@@ -4,8 +4,8 @@
     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-11-3</artifactId>
-    <name>core-java-11-3</name>
     <packaging>jar</packaging>
+    <name>core-java-11-3</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

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

@@ -4,8 +4,8 @@
     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-11</artifactId>
-    <name>core-java-11</name>
     <packaging>jar</packaging>
+    <name>core-java-11</name>
 
     <parent>
         <groupId>com.baeldung</groupId>
@@ -15,11 +15,6 @@
     </parent>
 
     <dependencies>
-        <dependency>
-            <groupId>com.google.guava</groupId>
-            <artifactId>guava</artifactId>
-            <version>${guava.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.openjdk.jmh</groupId>
             <artifactId>jmh-core</artifactId>

core-java-modules/core-java-12/pom.xml

@@ -4,8 +4,8 @@
     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-12</artifactId>
-    <name>core-java-12</name>
     <packaging>jar</packaging>
+    <name>core-java-12</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

core-java-modules/core-java-13/pom.xml

@@ -4,8 +4,8 @@
     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-13</artifactId>
-    <name>core-java-13</name>
     <packaging>jar</packaging>
+    <name>core-java-13</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

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

@@ -4,8 +4,8 @@
     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-14</artifactId>
-    <name>core-java-14</name>
     <packaging>jar</packaging>
+    <name>core-java-14</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

core-java-modules/core-java-15/pom.xml

@@ -4,8 +4,8 @@
     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-15</artifactId>
-    <name>core-java-15</name>
     <packaging>jar</packaging>
+    <name>core-java-15</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>
@@ -13,7 +13,6 @@
         <version>0.0.1-SNAPSHOT</version>
     </parent>
 
-
     <dependencies>
         <dependency>
             <groupId>org.apache.commons</groupId>

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

@@ -4,8 +4,8 @@
     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-16</artifactId>
-    <name>core-java-16</name>
     <packaging>jar</packaging>
+    <name>core-java-16</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

core-java-modules/core-java-17/pom.xml

@@ -4,8 +4,8 @@
     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-17</artifactId>
-    <name>core-java-17</name>
     <packaging>jar</packaging>
+    <name>core-java-17</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

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

@@ -4,8 +4,8 @@
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <artifactId>core-java-18</artifactId>
-    <name>core-java-18</name>
     <packaging>jar</packaging>
+    <name>core-java-18</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

core-java-modules/core-java-18/src/main/java/com/baeldung/inetspi/InetAddressSPI.java

@@ -0,0 +1,44 @@
+package com.baeldung.inetspi;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.Arrays;
+import java.util.stream.Stream;
+
+import com.baeldung.inetspi.providers.CustomAddressResolverImpl;
+
+public class InetAddressSPI {
+    public String usingGetByName(String host) throws UnknownHostException {
+        InetAddress inetAddress =  InetAddress.getByName(host);
+        return inetAddress.getHostAddress();
+    }
+
+    public String[] usingGetAllByName(String host) throws UnknownHostException {
+        InetAddress[] inetAddresses =  InetAddress.getAllByName(host);
+        return Arrays.stream(inetAddresses).map(InetAddress::getHostAddress).toArray(String[]::new);
+    }
+
+    public String usingGetByIp(byte[] ip) throws UnknownHostException {
+        InetAddress inetAddress =  InetAddress.getByAddress(ip);
+
+        return inetAddress.getHostName();
+    }
+
+    public String usingGetByIpAndReturnsCannonName(byte[] ip) throws UnknownHostException {
+        InetAddress inetAddress =  InetAddress.getByAddress(ip);
+
+        return inetAddress.getCanonicalHostName();
+    }
+
+    public String getHostUsingCustomImpl(byte[] ip) throws UnknownHostException {
+
+        CustomAddressResolverImpl imp = new CustomAddressResolverImpl();
+        return imp.get(null).lookupByAddress(ip);
+    }
+
+    public Stream<InetAddress> getIpUsingCustomImpl(String host) throws UnknownHostException {
+
+        CustomAddressResolverImpl imp = new CustomAddressResolverImpl();
+        return imp.get(null).lookupByName(host, null);
+    }
+}

core-java-modules/core-java-18/src/main/java/com/baeldung/inetspi/Registry.java

@@ -0,0 +1,56 @@
+package com.baeldung.inetspi;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.logging.Logger;
+import java.util.stream.Stream;
+
+public class Registry {
+    private final Map<String, List<byte[]>> registry;
+
+    private static final Logger LOGGER = Logger.getLogger(Registry.class.getName());
+
+    public Registry() {
+        registry = loadMapWithData();
+    }
+
+    public Stream<InetAddress> getAddressesfromHost(String host) throws UnknownHostException {
+        LOGGER.info("Performing Forward Lookup for HOST : " + host);
+        if (!registry.containsKey(host)) {
+            throw new UnknownHostException("Missing Host information in Resolver");
+        }
+        return registry.get(host)
+          .stream()
+          .map(add -> constructInetAddress(host, add))
+          .filter(Objects::nonNull);
+    }
+
+    public String getHostFromAddress(byte[] arr) throws UnknownHostException {
+        LOGGER.info("Performing Reverse Lookup for Address : " + Arrays.toString(arr));
+        for (Map.Entry<String, List<byte[]>> entry : registry.entrySet()) {
+            if (entry.getValue()
+              .stream()
+              .anyMatch(ba -> Arrays.equals(ba, arr))) {
+                return entry.getKey();
+            }
+        }
+        throw new UnknownHostException("Address Not Found");
+    }
+
+    private Map<String, List<byte[]>> loadMapWithData() {
+        return Map.of("baeldung-local.org", List.of(new byte[] { 1, 2, 3, 4 }));
+    }
+
+    private static InetAddress constructInetAddress(String host, byte[] address) {
+        try {
+            return InetAddress.getByAddress(host, address);
+        } catch (UnknownHostException unknownHostException) {
+            return null;
+        }
+    }
+
+}

core-java-modules/core-java-18/src/main/java/com/baeldung/inetspi/providers/CustomAddressResolverImpl.java

@@ -0,0 +1,42 @@
+package com.baeldung.inetspi.providers;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.net.spi.InetAddressResolver;
+import java.net.spi.InetAddressResolverProvider;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.logging.Logger;
+import java.util.stream.Stream;
+
+import com.baeldung.inetspi.Registry;
+
+public class CustomAddressResolverImpl extends InetAddressResolverProvider {
+
+    private static Logger LOGGER = Logger.getLogger(CustomAddressResolverImpl.class.getName());
+
+    private static Registry registry = new Registry();
+
+    @Override
+    public InetAddressResolver get(Configuration configuration) {
+        LOGGER.info("Using Custom Address Resolver :: " + this.name());
+        LOGGER.info("Registry initialised");
+        return new InetAddressResolver() {
+            @Override
+            public Stream<InetAddress> lookupByName(String host, LookupPolicy lookupPolicy) throws UnknownHostException {
+                return registry.getAddressesfromHost(host);
+            }
+
+            @Override
+            public String lookupByAddress(byte[] addr) throws UnknownHostException {
+                return registry.getHostFromAddress(addr);
+            }
+        };
+    }
+
+    @Override
+    public String name() {
+        return "CustomInternetAddressResolverImpl";
+    }
+}

core-java-modules/core-java-18/src/test/java/com/baeldung/inetspi/InetAddressSPIUnitTest.java

@@ -0,0 +1,31 @@
+package com.baeldung.inetspi;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.stream.Stream;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class InetAddressSPIUnitTest {
+    @Test
+    public void givenInetAddress_whenUsingInetAddress_thenPerformResolution() throws UnknownHostException {
+        InetAddressSPI spi = new InetAddressSPI();
+        Assert.assertNotNull(spi.usingGetByName("www.google.com"));
+        Assert.assertTrue(spi.usingGetAllByName("www.google.com").length > 1);
+        Assert.assertNotNull(spi.usingGetByIp(InetAddress.getByName("www.google.com")
+          .getAddress()));
+        Assert.assertNotNull(spi.usingGetByIpAndReturnsCannonName(InetAddress.getByName("www.google.com")
+          .getAddress()));
+    }
+
+    @Test
+    public void givenCustomInetAddressImplementation_whenUsingInetAddress_thenPerformResolution() throws UnknownHostException {
+        InetAddressSPI spi = new InetAddressSPI();
+        Assert.assertEquals("baeldung-local.org", spi.getHostUsingCustomImpl(new byte[] { 1, 2, 3, 4 }));
+        Stream<InetAddress> response = spi.getIpUsingCustomImpl("baeldung-local.org");
+        Assert.assertArrayEquals(new byte[] { 1, 2, 3, 4 }, response.findFirst()
+          .get()
+          .getAddress());
+    }
+}

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

@@ -13,4 +13,5 @@
 - [Format LocalDate to ISO 8601 With T and Z](https://www.baeldung.com/java-format-localdate-iso-8601-t-z)
 - [Check if Two Date Ranges Overlap](https://www.baeldung.com/java-check-two-date-ranges-overlap)
 - [Difference between ZoneOffset.UTC and ZoneId.of(“UTC”)](https://www.baeldung.com/java-zoneoffset-utc-zoneid-of)
+- [Check if a Given Time Lies Between Two Times Regardless of Date](https://www.baeldung.com/java-check-between-two-times)
 - [[<-- Prev]](/core-java-modules/core-java-datetime-java8-1)

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

@@ -4,8 +4,8 @@
     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-8-datetime-2</artifactId>
-    <name>core-java-8-datetime-2</name>
     <packaging>jar</packaging>
+    <name>core-java-8-datetime-2</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

core-java-modules/core-java-8-datetime-2/src/test/java/com/baeldung/checkiftimebetweentwotimes/CheckIfTimeBetweenTwoTimesUnitTest.java

@@ -0,0 +1,45 @@
+package com.baeldung.checkiftimebetweentwotimes;
+
+import org.junit.Test;
+
+import java.time.LocalTime;
+import java.util.Calendar;
+import java.util.Date;
+
+import static org.junit.Assert.assertTrue;
+
+public class CheckIfTimeBetweenTwoTimesUnitTest {
+    private LocalTime startTime = LocalTime.parse("09:00:00");
+    private LocalTime endTime = LocalTime.parse("17:00:00");
+    private LocalTime targetTime = LocalTime.parse("12:30:00");
+
+    @Test
+    public void givenLocalTime_whenUsingIsAfterIsBefore_thenTimeIsBetween() {
+        assertTrue(!targetTime.isBefore(startTime) && !targetTime.isAfter(endTime));
+    }
+
+    @Test
+    public void givenLocalTime_whenUsingCompareTo_thenTimeIsBetween() {
+        assertTrue(targetTime.compareTo(startTime) >= 0 && targetTime.compareTo(endTime) <= 0);
+    }
+
+    @Test
+    public void givenDate_whenUsingAfterBefore_thenTimeIsBetween() {
+        Calendar startCalendar = Calendar.getInstance();
+        startCalendar.set(Calendar.HOUR_OF_DAY, 9);
+        startCalendar.set(Calendar.MINUTE, 0);
+        Date startTime = startCalendar.getTime();
+
+        Calendar endCalendar = Calendar.getInstance();
+        endCalendar.set(Calendar.HOUR_OF_DAY, 17);
+        endCalendar.set(Calendar.MINUTE, 0);
+        Date endTime = endCalendar.getTime();
+
+        Calendar targetCalendar = Calendar.getInstance();
+        targetCalendar.set(Calendar.HOUR_OF_DAY, 12);
+        targetCalendar.set(Calendar.MINUTE, 30);
+        Date targetTime = targetCalendar.getTime();
+
+        assertTrue(!targetTime.before(startTime) && !targetTime.after(endTime));
+    }
+}

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

@@ -4,8 +4,8 @@
     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-8-datetime</artifactId>
-    <name>core-java-8-datetime</name>
     <packaging>jar</packaging>
+    <name>core-java-8-datetime</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

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

@@ -5,7 +5,7 @@ This module contains articles about Project Jigsaw and the Java Platform Module
 ### Relevant Articles:
 
 - [Introduction to Project Jigsaw](http://www.baeldung.com/project-jigsaw-java-modularity)
-- [A Guide to Java 9 Modularity](https://www.baeldung.com/java-9-modularity)
+- [A Guide to Java Modularity](https://www.baeldung.com/java-modularity)
 - [Java 9 java.lang.Module API](https://www.baeldung.com/java-9-module-api)
 - [Java 9 Illegal Reflective Access Warning](https://www.baeldung.com/java-illegal-reflective-access)
 - [Java Modularity and Unit Testing](https://www.baeldung.com/java-modularity-unit-testing)

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

@@ -3,20 +3,14 @@
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
+    <artifactId>library-core</artifactId>
+
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>
         <artifactId>core-java-9-jigsaw</artifactId>
         <version>0.0.1-SNAPSHOT</version>
     </parent>
 
-    <artifactId>library-core</artifactId>
-
-    <properties>
-        <maven.compiler.source>19</maven.compiler.source>
-        <maven.compiler.target>19</maven.compiler.target>
-        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-    </properties>
-
     <dependencies>
         <dependency>
             <groupId>org.junit.jupiter</groupId>
@@ -52,4 +46,11 @@
             </plugin>
         </plugins>
     </build>
+
+    <properties>
+        <maven.compiler.source>19</maven.compiler.source>
+        <maven.compiler.target>19</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+    
 </project>

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

@@ -4,8 +4,9 @@
     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-9-jigsaw</artifactId>
-    <name>core-java-9-jigsaw</name>
     <packaging>pom</packaging>
+    <name>core-java-9-jigsaw</name>
+
     <modules>
         <module>library-core</module>
     </modules>

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

@@ -4,8 +4,8 @@
     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-9-streams</artifactId>
-    <name>core-java-9-streams</name>
     <packaging>jar</packaging>
+    <name>core-java-9-streams</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

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

@@ -4,8 +4,8 @@
     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-annotations</artifactId>
-    <name>core-java-annotations</name>
     <packaging>jar</packaging>
+    <name>core-java-annotations</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

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

@@ -4,8 +4,8 @@
     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-arrays-convert</artifactId>
-    <name>core-java-arrays-convert</name>
     <packaging>jar</packaging>
+    <name>core-java-arrays-convert</name>
 
     <parent>
         <artifactId>core-java-modules</artifactId>
@@ -20,4 +20,5 @@
             <version>${commons-lang3.version}</version>
         </dependency>
     </dependencies>
+
 </project>

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

@@ -4,8 +4,8 @@
     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-arrays-guides</artifactId>
-    <name>core-java-arrays-guides</name>
     <packaging>jar</packaging>
+    <name>core-java-arrays-guides</name>
 
     <parent>
         <artifactId>core-java-modules</artifactId>

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

@@ -4,8 +4,8 @@
     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-arrays-multidimensional</artifactId>
-    <name>core-java-arrays-multidimensional</name>
     <packaging>jar</packaging>
+    <name>core-java-arrays-multidimensional</name>
 
     <parent>
         <artifactId>core-java-modules</artifactId>

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

@@ -2,3 +2,4 @@
 - [Find the Middle Element of an Array in Java](https://www.baeldung.com/java-array-middle-item)
 - [Find the Equilibrium Indexes of an Array in Java](https://www.baeldung.com/java-equilibrium-index-array)
 - [Moves Zeros to the End of an Array in Java](https://www.baeldung.com/java-array-sort-move-zeros-end)
+- [Finding the Majority Element of an Array in Java](https://www.baeldung.com/java-array-find-majority-element)

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

@@ -4,8 +4,8 @@
     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-arrays-operations-advanced-2</artifactId>
-    <name>core-java-arrays-operations-advanced-2</name>
     <packaging>jar</packaging>
+    <name>core-java-arrays-operations-advanced-2</name>
 
     <parent>
         <artifactId>core-java-modules</artifactId>

core-java-modules/core-java-arrays-operations-advanced-2/src/main/java/com/baeldung/majorityelement/FindMajorityElement.java

@@ -0,0 +1,95 @@
+package com.baeldung.majorityelement;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+
+public class FindMajorityElement {
+
+    public static Integer findMajorityElementUsingForLoop(int[] nums) {
+        int majorityThreshold = nums.length / 2;
+        Integer majorityElement = null;
+        for (int i = 0; i < nums.length; i++) {
+            int count = 0;
+            for (int j = 0; j < nums.length; j++) {
+                if (nums[i] == nums[j]) {
+                    count++;
+                }
+            }
+            if (count > majorityThreshold) {
+                return majorityElement = nums[i];
+            }
+        }
+        return majorityElement;
+    }
+
+    public static Integer findMajorityElementUsingSorting(int[] nums) {
+        Arrays.sort(nums);
+        int majorityThreshold = nums.length / 2;
+        int count = 0;
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] == nums[majorityThreshold]) {
+                count++;
+            }
+
+            if (count > majorityThreshold) {
+                return nums[majorityThreshold];
+            }
+        }
+        return null;
+    }
+
+    public static Integer findMajorityElementUsingHashMap(int[] nums) {
+        Map<Integer, Integer> frequencyMap = new HashMap<>();
+
+        for (int num : nums) {
+            frequencyMap.put(num, frequencyMap.getOrDefault(num, 0) + 1);
+        }
+
+        int majorityThreshold = nums.length / 2;
+        for (Map.Entry<Integer, Integer> entry : frequencyMap.entrySet()) {
+            if (entry.getValue() > majorityThreshold) {
+                return entry.getKey();
+            }
+        }
+        return null;
+    }
+
+    public static Integer findMajorityElementUsingMooreVoting(int[] nums) {
+        int majorityThreshold = nums.length / 2;
+        int candidate = nums[0];
+        int count = 1;
+
+        for (int i = 1; i < nums.length; i++) {
+            if (count == 0) {
+                candidate = nums[i];
+                count = 1;
+            } else if (candidate == nums[i]) {
+                count++;
+            } else {
+                count--;
+            }
+
+            System.out.println("Iteration " + i + ": [candidate - " + candidate + ", count - " + count + ", element - " + nums[i] + "]");
+        }
+
+        count = 0;
+        for (int num : nums) {
+            if (num == candidate) {
+                count++;
+            }
+        }
+        return count > majorityThreshold ? candidate : null;
+    }
+
+    public static void main(String[] args) {
+        int[] nums = {  2, 3, 2, 4, 2, 5, 2 };
+        Integer majorityElement = findMajorityElementUsingMooreVoting(nums);
+
+        if (majorityElement != null) {
+            System.out.println("Majority element with maximum occurrences: " + majorityElement);
+        } else {
+            System.out.println("No majority element found");
+        }
+    }
+}

core-java-modules/core-java-arrays-operations-advanced-2/src/test/java/com/baeldung/majorityelement/FindMajorityElementUnitTest.java

@@ -0,0 +1,64 @@
+package com.baeldung.majorityelement;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class FindMajorityElementUnitTest {
+
+    @Test
+    void givenArrayWithMajorityElement_WhenUsingForLoop_ThenReturnFound() {
+        int[] nums = { 2, 3, 2, 4, 2, 5, 2 };
+        Integer result = FindMajorityElement.findMajorityElementUsingForLoop(nums);
+        assertEquals(2, result);
+    }
+
+    @Test
+    void givenArrayWithoutMajorityElement_WhenUsingForLoop_ThenNotFound() {
+        int[] nums = { 2, 2, 3, 3 };
+        Integer result = FindMajorityElement.findMajorityElementUsingForLoop(nums);
+        assertEquals(null, result);
+    }
+
+    @Test
+    public void givenArrayWithMajorityElement_WhenUsingSorting_ThenReturnFound() {
+        int[] nums = { 2, 3, 2, 4, 2, 5, 2 };
+        Integer result = FindMajorityElement.findMajorityElementUsingSorting(nums);
+        assertEquals(2, result);
+    }
+
+    @Test
+    public void givenArrayWithoutMajorityElement_WhenUsingSorting_ThenNotFound() {
+        int[] nums = { 2, 2, 3, 3 };
+        Integer result = FindMajorityElement.findMajorityElementUsingSorting(nums);
+        assertEquals(null, result);
+    }
+
+    @Test
+    void givenArrayWithMajorityElement_WhenUsingHashMap_ThenReturnFound() {
+        int[] nums = { 2, 3, 2, 4, 2, 5, 2 };
+        Integer result = FindMajorityElement.findMajorityElementUsingHashMap(nums);
+        assertEquals(2, result);
+    }
+
+    @Test
+    void givenArrayWithoutMajorityElement_WhenUsingHashMap_ThenNotFound() {
+        int[] nums = { 2, 2, 3, 3 };
+        Integer result = FindMajorityElement.findMajorityElementUsingHashMap(nums);
+        assertEquals(null, result);
+    }
+
+    @Test
+    void givenArrayWithMajorityElement_WhenUsingMooreVoting_ThenReturnFound() {
+        int[] nums = { 2, 3, 2, 4, 2, 5, 2 };
+        Integer result = FindMajorityElement.findMajorityElementUsingMooreVoting(nums);
+        assertEquals(2, result);
+    }
+
+    @Test
+    void givenArrayWithoutMajorityElement_WhenUsingMooreVoting_ThenNotFound() {
+        int[] nums = { 2, 2, 3, 3 };
+        Integer result = FindMajorityElement.findMajorityElementUsingMooreVoting(nums);
+        assertEquals(null, result);
+    }
+}

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

@@ -4,8 +4,8 @@
     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-arrays-operations-advanced</artifactId>
-    <name>core-java-arrays-operations-advanced</name>
     <packaging>jar</packaging>
+    <name>core-java-arrays-operations-advanced</name>
 
     <parent>
         <artifactId>core-java-modules</artifactId>

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

@@ -4,8 +4,8 @@
     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-arrays-operations-basic-2</artifactId>
-    <name>core-java-arrays-operations-basic-2</name>
     <packaging>jar</packaging>
+    <name>core-java-arrays-operations-basic-2</name>
 
     <parent>
         <artifactId>core-java-modules</artifactId>

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

@@ -4,8 +4,8 @@
     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-arrays-operations-basic</artifactId>
-    <name>core-java-arrays-operations-basic</name>
     <packaging>jar</packaging>
+    <name>core-java-arrays-operations-basic</name>
 
     <parent>
         <artifactId>core-java-modules</artifactId>

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

@@ -4,8 +4,8 @@
     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-arrays-sorting</artifactId>
-    <name>core-java-arrays-sorting</name>
     <packaging>jar</packaging>
+    <name>core-java-arrays-sorting</name>
 
     <parent>
         <artifactId>core-java-modules</artifactId>

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

@@ -4,8 +4,8 @@
     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-booleans</artifactId>
-    <name>core-java-booleans</name>
     <packaging>jar</packaging>
+    <name>core-java-booleans</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

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

@@ -4,8 +4,8 @@
     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-char</artifactId>
-    <name>core-java-char</name>
     <packaging>jar</packaging>
+    <name>core-java-char</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

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

@@ -4,8 +4,8 @@
     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>
-    <name>core-java-collections-2</name>
     <packaging>jar</packaging>
+    <name>core-java-collections-2</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

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

@@ -4,8 +4,8 @@
     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-3</artifactId>
-    <name>core-java-collections-3</name>
     <packaging>jar</packaging>
+    <name>core-java-collections-3</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

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

@@ -4,8 +4,8 @@
     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-4</artifactId>
-    <name>core-java-collections-4</name>
     <packaging>jar</packaging>
+    <name>core-java-collections-4</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

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

@@ -4,8 +4,8 @@
     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-5</artifactId>
-    <name>core-java-collections-5</name>
     <packaging>jar</packaging>
+    <name>core-java-collections-5</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

core-java-modules/core-java-collections-5/src/test/java/com/baeldung/immutables/ImmutableCollectionsUnitTest.java

@@ -0,0 +1,54 @@
+package com.baeldung.immutables;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+class ImmutableCollectionsUnitTest {
+
+    @Test
+    void givenUnmodifiableMap_whenPutNewEntry_thenThrowsUnsupportedOperationException() {
+        Map<String, String> modifiableMap = new HashMap<>();
+        modifiableMap.put("name1", "Michael");
+        modifiableMap.put("name2", "Harry");
+
+        Map<String, String> unmodifiableMap = Collections.unmodifiableMap(modifiableMap);
+
+        assertThrows(UnsupportedOperationException.class, () -> unmodifiableMap.put("name3", "Micky"));
+    }
+
+    @Test
+    void givenUnmodifiableMap_whenPutNewEntryUsingOriginalReference_thenSuccess() {
+        Map<String, String> modifiableMap = new HashMap<>();
+        modifiableMap.put("name1", "Michael");
+        modifiableMap.put("name2", "Harry");
+
+        Map<String, String> unmodifiableMap = Collections.unmodifiableMap(modifiableMap);
+        modifiableMap.put("name3", "Micky");
+
+        assertEquals(modifiableMap, unmodifiableMap);
+        assertTrue(unmodifiableMap.containsKey("name3"));
+    }
+
+    @Test
+    void givenImmutableMap_whenPutNewEntry_thenThrowsUnsupportedOperationException() {
+        Map<String, String> immutableMap = Map.of("name1", "Michael", "name2", "Harry");
+
+        assertThrows(UnsupportedOperationException.class, () -> immutableMap.put("name3", "Micky"));
+    }
+
+    @Test
+    void givenImmutableMap_whenUsecopyOf_thenExceptionOnPut() {
+        Map<String, String> immutableMap = Map.of("name1", "Michael", "name2", "Harry");
+        Map<String, String> copyOfImmutableMap = Map.copyOf(immutableMap);
+
+        assertThrows(UnsupportedOperationException.class, () -> copyOfImmutableMap.put("name3", "Micky"));
+    }
+}
+

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

@@ -4,3 +4,4 @@ This module contains articles about the Java ArrayList collection
 
 ### Relevant Articles:
 - [Create an ArrayList with Multiple Object Types](https://www.baeldung.com/java-arraylist-multiple-object-types)
+- [Finding the Peak Elements of a List](https://www.baeldung.com/java-list-find-peak)

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

@@ -3,8 +3,8 @@
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <artifactId>core-java-collections-array-list-2</artifactId>
-    <name>core-java-collections-array-list-2</name>
     <packaging>jar</packaging>
+    <name>core-java-collections-array-list-2</name>
 
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

core-java-modules/core-java-collections-array-list-2/src/main/java/com/baeldung/peakelements/MultiplePeakFinder.java

@@ -0,0 +1,40 @@
+package com.baeldung.peakelements;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class MultiplePeakFinder {
+
+    public static List<Integer> findPeaks(int[] arr) {
+
+        List<Integer> peaks = new ArrayList<>();
+
+        if (arr == null || arr.length == 0) {
+            return peaks;
+        }
+        findPeakElements(arr, 0, arr.length - 1, peaks, arr.length);
+        return peaks;
+    }
+
+    private static void findPeakElements(int[] arr, int low, int high, List<Integer> peaks, int length) {
+
+        if (low > high) {
+            return;
+        }
+
+        int mid = low + (high - low) / 2;
+
+        boolean isPeak = (mid == 0 || arr[mid] > arr[mid - 1]) && (mid == length - 1 || arr[mid] > arr[mid + 1]);
+        boolean isFirstInSequence = mid > 0 && arr[mid] == arr[mid - 1] && arr[mid] > arr[mid + 1];
+
+        if (isPeak || isFirstInSequence) {
+
+            if (!peaks.contains(arr[mid])) {
+                peaks.add(arr[mid]);
+            }
+        }
+
+        findPeakElements(arr, low, mid - 1, peaks, length);
+        findPeakElements(arr, mid + 1, high, peaks, length);
+    }
+}

core-java-modules/core-java-collections-array-list-2/src/main/java/com/baeldung/peakelements/PeakElementFinder.java

@@ -0,0 +1,44 @@
+package com.baeldung.peakelements;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class PeakElementFinder {
+    public List<Integer> findPeakElements(int[] arr) {
+        int n = arr.length;
+        List<Integer> peaks = new ArrayList<>();
+
+        if (n == 0) {
+            return peaks;
+        }
+
+        for (int i = 0; i < n; i++) {
+            if (isPeak(arr, i, n)) {
+                peaks.add(arr[i]);
+            }
+
+            while (i < n - 1 && arr[i] == arr[i + 1]) {
+                i++;
+            }
+        }
+
+        return peaks;
+    }
+
+    private boolean isPeak(int[] arr, int index, int n) {
+        if (index == 0) {
+            return n > 1 ? arr[index] >= arr[index + 1] : true;
+        } else if (index == n - 1) {
+            return arr[index] >= arr[index - 1];
+        } else if (arr[index] == arr[index + 1] && arr[index] > arr[index - 1]) {
+            int i = index;
+
+            while (i < n - 1 && arr[i] == arr[i + 1]) {
+                i++;
+            }
+            return i == n - 1 || arr[i] > arr[i + 1];
+        } else {
+            return arr[index] >= arr[index - 1] && arr[index] >= arr[index + 1];
+        }
+    }
+}