Merge branch 'eugenp:master' into danielmcnally285_return_first_non_null

algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/connect4/GameBoard.java

@@ -0,0 +1,129 @@
+package com.baeldung.algorithms.connect4;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class GameBoard {
+    private final List<List<Piece>> columns;
+
+    private final int rows;
+
+    public GameBoard(int columns, int rows) {
+        this.rows = rows;
+        this.columns = new ArrayList<>();
+
+        for (int i = 0; i < columns; ++i) {
+            this.columns.add(new ArrayList<>());
+        }
+    }
+
+    public int getRows() {
+        return rows;
+    }
+
+    public int getColumns() {
+        return columns.size();
+    }
+
+    public Piece getCell(int x, int y) {
+        assert(x >= 0 && x < getColumns());
+        assert(y >= 0 && y < getRows());
+
+        List<Piece> column = columns.get(x);
+
+        if (column.size() > y) {
+            return column.get(y);
+        } else {
+            return null;
+        }
+    }
+
+    public boolean move(int x, Piece player) {
+        assert(x >= 0 && x < getColumns());
+
+        List<Piece> column = columns.get(x);
+
+        if (column.size() >= this.rows) {
+            throw new IllegalArgumentException("That column is full");
+        }
+
+        column.add(player);
+
+        return checkWin(x, column.size() - 1, player);
+    }
+
+    private boolean checkWin(int x, int y, Piece player) {
+        // Vertical line
+        if (checkLine(x, y, 0, -1, player)) {
+            return true;
+        }
+
+        for (int offset = 0; offset < 4; ++offset) {
+            // Horizontal line
+            if (checkLine(x - 3 + offset, y, 1, 0, player)) {
+                return true;
+            }
+
+            // Leading diagonal
+            if (checkLine(x - 3 + offset, y + 3 - offset, 1, -1, player)) {
+                return true;
+            }
+
+            // Trailing diagonal
+            if (checkLine(x - 3 + offset, y - 3 + offset, 1, 1, player)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    private boolean checkLine(int x1, int y1, int xDiff, int yDiff, Piece player) {
+        for (int i = 0; i < 4; ++i) {
+            int x = x1 + (xDiff * i);
+            int y = y1 + (yDiff * i);
+
+            if (x < 0 || x > columns.size() - 1) {
+                return false;
+            }
+
+            if (y < 0 || y > rows - 1) {
+                return false;
+            }
+
+            if (player != getCell(x, y)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder result = new StringBuilder();
+
+        for (int y = getRows() - 1; y >= 0; --y) {
+            for (int x = 0; x < getColumns(); ++x) {
+                Piece piece = getCell(x, y);
+
+                result.append("|");
+                if (piece == null) {
+                    result.append(" ");
+                } else if (piece == Piece.PLAYER_1) {
+                    result.append("X");
+                } else if (piece == Piece.PLAYER_2) {
+                    result.append("O");
+                }
+            }
+
+            result.append("|\n");
+            for (int i = 0; i < getColumns(); ++i) {
+                result.append("+-");
+            }
+            result.append("+\n");
+        }
+
+        return result.toString();
+    }
+}

algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/connect4/GameUnitTest.java

@@ -0,0 +1,40 @@
+package com.baeldung.algorithms.connect4;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class GameUnitTest {
+    @Test
+    public void blankGame() {
+        GameBoard gameBoard = new GameBoard(8, 6);
+
+        System.out.println(gameBoard);
+    }
+
+    @Test
+    public void playedGame() {
+        GameBoard gameBoard = new GameBoard(8, 6);
+
+        assertFalse(gameBoard.move(3, Piece.PLAYER_1));
+        assertFalse(gameBoard.move(2, Piece.PLAYER_2));
+
+        assertFalse(gameBoard.move(4, Piece.PLAYER_1));
+        assertFalse(gameBoard.move(3, Piece.PLAYER_2));
+
+        assertFalse(gameBoard.move(5, Piece.PLAYER_1));
+        assertFalse(gameBoard.move(6, Piece.PLAYER_2));
+
+        assertFalse(gameBoard.move(5, Piece.PLAYER_1));
+        assertFalse(gameBoard.move(4, Piece.PLAYER_2));
+
+        assertFalse(gameBoard.move(5, Piece.PLAYER_1));
+        assertFalse(gameBoard.move(5, Piece.PLAYER_2));
+
+        assertFalse(gameBoard.move(6, Piece.PLAYER_1));
+        assertTrue(gameBoard.move(4, Piece.PLAYER_2));
+
+        System.out.println(gameBoard);
+    }
+}

algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/connect4/Piece.java

@@ -0,0 +1,6 @@
+package com.baeldung.algorithms.connect4;
+
+public enum Piece {
+    PLAYER_1,
+    PLAYER_2
+}

aws-modules/aws-miscellaneous/README.md

@@ -5,6 +5,5 @@ This module contains articles about various Amazon Web Services (AWS) such as EC
 ### Relevant articles
 
 - [Managing EC2 Instances in Java](https://www.baeldung.com/ec2-java)
-- [Integration Testing with a Local DynamoDB Instance](https://www.baeldung.com/dynamodb-local-integration-tests)
 - [Managing Amazon SQS Queues in Java](https://www.baeldung.com/aws-queues-java)
 - [Guide to AWS Aurora RDS with Java](https://www.baeldung.com/aws-aurora-rds-java)

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

@@ -11,5 +11,5 @@ This module contains articles about Java 8 core features
 - [Finding Min/Max in an Array with Java](https://www.baeldung.com/java-array-min-max)
 - [Internationalization and Localization in Java 8](https://www.baeldung.com/java-8-localization)
 - [Generalized Target-Type Inference in Java](https://www.baeldung.com/java-generalized-target-type-inference)
-- [Monads in Java](https://www.baeldung.com/java-monads)
+- [Monads in Java – Optional](https://www.baeldung.com/java-monads)
 - [[More -->]](/core-java-modules/core-java-8-2)

core-java-modules/core-java-8/src/main/java/com/baeldung/spliterator/CustomSpliterator.java

@@ -0,0 +1,48 @@
+package com.baeldung.spliterator;
+
+import java.util.List;
+import java.util.Spliterator;
+import java.util.function.Consumer;
+
+public class CustomSpliterator implements Spliterator<Integer> {
+    private final List<Integer> elements;
+    private int currentIndex;
+    
+    public CustomSpliterator(List<Integer> elements) {
+        this.elements = elements;
+        this.currentIndex = 0;
+    }
+    
+    @Override
+    public boolean tryAdvance(Consumer<? super Integer> action) {
+        if (currentIndex < elements.size()) {
+            action.accept(elements.get(currentIndex));
+            currentIndex++;
+            return true;
+        }
+        return false;
+    }
+    
+    @Override
+    public Spliterator<Integer> trySplit() {
+        int currentSize = elements.size() - currentIndex;
+        if (currentSize < 2) {
+            return null;
+        }
+        
+        int splitIndex = currentIndex + currentSize / 2;
+        CustomSpliterator newSpliterator = new CustomSpliterator(elements.subList(currentIndex, splitIndex));
+        currentIndex = splitIndex;
+        return newSpliterator;
+    }
+    
+    @Override
+    public long estimateSize() {
+        return elements.size() - currentIndex;
+    }
+    
+    @Override
+    public int characteristics() {
+        return ORDERED | SIZED | SUBSIZED | NONNULL;
+    }
+} 

core-java-modules/core-java-8/src/main/java/com/baeldung/spliterator/Executor.java

@@ -1,12 +0,0 @@
-package com.baeldung.spliterator;
-
-import java.util.stream.Stream;
-
-public class Executor {
-
-	public static int countAutors(Stream<Author> stream) {
-		RelatedAuthorCounter wordCounter = stream.reduce(new RelatedAuthorCounter(0, true),
-				RelatedAuthorCounter::accumulate, RelatedAuthorCounter::combine);
-		return wordCounter.getCounter();
-	}
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/spliterator/RelatedAuthorCounter.java

@@ -1,27 +0,0 @@
-package com.baeldung.spliterator;
-
-public class RelatedAuthorCounter {
-    private final int counter;
-    private final boolean isRelated;
-
-    public RelatedAuthorCounter(int counter, boolean isRelated) {
-        this.counter = counter;
-        this.isRelated = isRelated;
-    }
-
-    public RelatedAuthorCounter accumulate(Author author) {
-        if (author.getRelatedArticleId() == 0) {
-            return isRelated ? this : new RelatedAuthorCounter(counter, true);
-        } else {
-            return isRelated ? new RelatedAuthorCounter(counter + 1, false) : this;
-        }
-    }
-
-    public RelatedAuthorCounter combine(RelatedAuthorCounter RelatedAuthorCounter) {
-        return new RelatedAuthorCounter(counter + RelatedAuthorCounter.counter, RelatedAuthorCounter.isRelated);
-    }
-
-    public int getCounter() {
-        return counter;
-    }
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/spliterator/RelatedAuthorSpliterator.java

@@ -1,49 +0,0 @@
-package com.baeldung.spliterator;
-
-import java.util.List;
-import java.util.Spliterator;
-import java.util.concurrent.atomic.AtomicInteger;
-import java.util.function.Consumer;
-
-public class RelatedAuthorSpliterator implements Spliterator<Author> {
-	private final List<Author> list;
-	AtomicInteger current = new AtomicInteger();
-
-	public RelatedAuthorSpliterator(List<Author> list) {
-		this.list = list;
-	}
-
-	@Override
-	public boolean tryAdvance(Consumer<? super Author> action) {
-
-		action.accept(list.get(current.getAndIncrement()));
-		return current.get() < list.size();
-	}
-
-	@Override
-	public Spliterator<Author> trySplit() {
-		int currentSize = list.size() - current.get();
-		if (currentSize < 10) {
-			return null;
-		}
-		for (int splitPos = currentSize / 2 + current.intValue(); splitPos < list.size(); splitPos++) {
-			if (list.get(splitPos).getRelatedArticleId() == 0) {
-				Spliterator<Author> spliterator = new RelatedAuthorSpliterator(list.subList(current.get(), splitPos));
-				current.set(splitPos);
-				return spliterator;
-			}
-		}
-		return null;
-	}
-
-	@Override
-	public long estimateSize() {
-		return list.size() - current.get();
-	}
-
-	@Override
-	public int characteristics() {
-		return CONCURRENT;
-	}
-
-}

core-java-modules/core-java-8/src/test/java/com/baeldung/spliterator/ExecutorUnitTest.java

@@ -6,10 +6,10 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Spliterator;
+import java.util.concurrent.ForkJoinPool;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
-import java.util.stream.StreamSupport;
-
 import org.junit.Before;
 import org.junit.Test;
 
@@ -18,22 +18,50 @@ import lombok.extern.slf4j.Slf4j;
 @Slf4j
 public class ExecutorUnitTest {
     Article article;
-    Stream<Author> stream;
-    Spliterator<Author> spliterator;
 
     @Before
     public void init() {
         article = new Article(Arrays.asList(new Author("Ahmad", 0), new Author("Eugen", 0), new Author("Alice", 1), new Author("Alice", 1), new Author("Mike", 0), new Author("Alice", 1), new Author("Mike", 0), new Author("Alice", 1), new Author("Mike", 0),
             new Author("Alice", 1), new Author("Mike", 0), new Author("Mike", 0), new Author("Alice", 1), new Author("Mike", 0), new Author("Alice", 1), new Author("Mike", 0), new Author("Alice", 1), new Author("Mike", 0), new Author("Alice", 1),
             new Author("Mike", 0), new Author("Michał", 0), new Author("Loredana", 1)), 0);
-
-        spliterator = new RelatedAuthorSpliterator(article.getListOfAuthors());
     }
 
     @Test
-    public void givenAstreamOfAuthors_whenProcessedInParallelWithCustomSpliterator_coubtProducessRightOutput() {
-        Stream<Author> stream2 = StreamSupport.stream(spliterator, true);
-        assertThat(Executor.countAutors(stream2.parallel())).isEqualTo(9);
+    public void givenAStreamOfIntegers_whenProcessedSequentialCustomSpliterator_countProducesRightOutput() {
+        List<Integer> numbers = new ArrayList<>();
+        numbers.add(1);
+        numbers.add(2);
+        numbers.add(3);
+        numbers.add(4);
+        numbers.add(5);
+
+        CustomSpliterator customSpliterator = new CustomSpliterator(numbers);
+
+        AtomicInteger sum = new AtomicInteger();
+
+        customSpliterator.forEachRemaining(sum::addAndGet);
+        assertThat(sum.get()).isEqualTo(15);
+    }
+
+    @Test
+    public void givenAStreamOfIntegers_whenProcessedInParallelWithCustomSpliterator_countProducesRightOutput() {
+        List<Integer> numbers = new ArrayList<>();
+        numbers.add(1);
+        numbers.add(2);
+        numbers.add(3);
+        numbers.add(4);
+        numbers.add(5);
+
+        CustomSpliterator customSpliterator = new CustomSpliterator(numbers);
+
+        // Create a ForkJoinPool for parallel processing
+        ForkJoinPool forkJoinPool = ForkJoinPool.commonPool();
+
+        AtomicInteger sum = new AtomicInteger(0);
+
+        // Process elements in parallel using parallelStream
+        forkJoinPool.submit(() -> customSpliterator.forEachRemaining(sum::addAndGet)).join();
+        assertThat(sum.get()).isEqualTo(15);
     }
 
     @Test
@@ -43,9 +71,7 @@ public class ExecutorUnitTest {
             .collect(Collectors.toList());
 
         Spliterator<Article> spliterator = articles.spliterator();
-        while (spliterator.tryAdvance(article -> article.setName(article.getName()
-            .concat("- published by Baeldung"))))
-            ;
+        while(spliterator.tryAdvance(article -> article.setName(article.getName().concat("- published by Baeldung"))));
 
         articles.forEach(article -> assertThat(article.getName()).isEqualTo("Java- published by Baeldung"));
     }

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

@@ -57,5 +57,9 @@
             </plugin>
         </plugins>
     </build>
+    
+    <properties>
+        <maven.compiler.release>11</maven.compiler.release>
+    </properties>
 
 </project>

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arraycompare/ArraysCompareUnitTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.arraycompare;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Arrays;
+
+import org.junit.jupiter.api.Test;
+
+class ArraysCompareUnitTest {
+
+    @Test
+    void givenSameContents_whenCompare_thenCorrect() {
+        String[] array1 = new String[] { "A", "B", "C" };
+        String[] array2 = new String[] { "A", "B", "C" };
+
+        assertThat(Arrays.compare(array1, array2)).isEqualTo(0);
+    }
+
+    @Test
+    void givenDifferentContents_whenCompare_thenDifferent() {
+        String[] array1 = new String[] { "A", "B", "C" };
+        String[] array2 = new String[] { "A", "C", "B", "D" };
+
+        assertThat(Arrays.compare(array1, array2)).isLessThan(0);
+        assertThat(Arrays.compare(array2, array1)).isGreaterThan(0);
+        assertThat(Arrays.compare(array1, null)).isGreaterThan(0);
+    }
+
+}

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

@@ -0,0 +1,6 @@
+## Core Java Arrays - Basic Operations
+
+This module contains articles about Java array fundamentals. They assume no previous background knowledge on working with arrays.
+
+### Relevant Articles: 
+- [Arrays mismatch() Method in Java](https://www.baeldung.com/java-arrays-mismatch)

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

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-arrays-operations-basic-2</artifactId>
+    <name>core-java-arrays-operations-basic-2</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <artifactId>core-java-modules</artifactId>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+
+</project>

core-java-modules/core-java-arrays-operations-basic-2/src/test/java/com/baeldung/array/mismatch/ArrayMismatchUnitTest.java

@@ -0,0 +1,269 @@
+package com.baeldung.array.mismatch;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.util.Arrays;
+import java.util.Comparator;
+
+import org.junit.jupiter.api.Test;
+
+class ArrayMismatchUnitTest {
+    
+    @Test
+    void givenTwoArraysWithACommonPrefix_whenMismatch_thenIndexOfFirstMismatch() {
+        int[] firstArray = {1, 2, 3, 4, 5};
+        int[] secondArray = {1, 2, 3, 5, 8};
+        assertEquals(3, Arrays.mismatch(firstArray, secondArray));
+    }
+    
+    @Test
+    void givenTwoIdenticalArrays_whenMismatch_thenMinusOne() {
+        int[] firstArray = {1, 2, 3, 4, 5};
+        int[] secondArray = {1, 2, 3, 4, 5};
+        assertEquals(-1, Arrays.mismatch(firstArray, secondArray));
+    }
+    
+    @Test
+    void givenFirstArrayIsAPrefixOfTheSecond_whenMismatch_thenFirstArrayLength() {
+        int[] firstArray = {1, 2, 3, 4, 5};
+        int[] secondArray = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+        assertEquals(firstArray.length, Arrays.mismatch(firstArray, secondArray));
+    }
+    
+    @Test
+    void givenNoCommonPrefix_whenMismatch_thenZero() {
+        int[] firstArray = {1, 2, 3, 4, 5};
+        int[] secondArray = {9, 8, 7};
+        assertEquals(0, Arrays.mismatch(firstArray, secondArray));
+    }
+    
+    @Test
+    void givenAtLeastANullArray_whenMismatch_thenThrowsNullPointerException() {
+        int[] firstArray = null;
+        int[] secondArray = {1, 2, 3, 4, 5};
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(firstArray, secondArray));
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(secondArray, firstArray));
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(firstArray, firstArray));
+    }
+    
+    @Test
+    void givenExactlyOneAnEmptyArray_whenMismatch_thenZero() {
+        int[] firstArray = {};
+        int[] secondArray = {1, 2, 3};
+        assertEquals(0, Arrays.mismatch(firstArray, secondArray));
+        assertEquals(0, Arrays.mismatch(secondArray, firstArray));
+    }
+    
+    @Test
+    void givenTwoEmptyArrays_whenMismatch_thenMinusOne() {
+        assertEquals(-1, Arrays.mismatch(new int[] {}, new int[] {}));
+    }
+    
+    @Test
+    void givenTwoSubArraysWithACommonPrefix_whenMismatch_thenIndexOfFirstMismatch() {
+        int[] firstArray = {1, 2, 3, 4, 5};
+        int[] secondArray = {0, 1, 2, 3, 5, 8};
+        assertEquals(3, Arrays.mismatch(firstArray, 0, 4, secondArray, 1, 6));
+    }
+    
+    @Test
+    void givenTwoIdenticalSubArrays_whenMismatch_thenMinusOne() {
+        int[] firstArray = {0, 0, 1, 2};
+        int[] secondArray = {0, 1, 2, 3, 4};
+        assertEquals(-1, Arrays.mismatch(firstArray, 2, 4, secondArray, 1, 3));
+    }
+    
+    @Test
+    void givenFirstSubArrayIsAPrefixOfTheSecond_whenMismatch_thenFirstArrayLength() {
+        int[] firstArray = {2, 3, 4, 5, 4, 3, 2};
+        int[] secondArray = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+        assertEquals(4, Arrays.mismatch(firstArray, 0, 4, secondArray, 2, 9));
+    }
+    
+    @Test
+    void givenNoCommonPrefixForSubArrays_whenMismatch_thenZero() {
+        int[] firstArray = {0, 0, 0, 0, 0};
+        int[] secondArray = {9, 8, 7, 6, 5};
+        assertEquals(0, Arrays.mismatch(firstArray, 1, 2, secondArray, 1, 2));
+    }
+    
+    @Test
+    void givenAtLeastANullSubArray_whenMismatch_thenThrowsNullPointerException() {
+        int[] firstArray = null;
+        int[] secondArray = {1, 2, 3, 4, 5};
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(firstArray, 0, 1, secondArray, 0, 1));
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(secondArray, 0, 1, firstArray, 0, 1));
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(firstArray, 0, 1, firstArray, 0, 1));
+    }
+    
+    @Test
+    void givenExactlyOneEmptySubArray_whenMismatch_thenZero() {
+        int[] firstArray = {1};
+        int[] secondArray = {1, 2, 3};
+        assertEquals(0, Arrays.mismatch(firstArray, 0, 0, secondArray, 0, 2));
+        assertEquals(0, Arrays.mismatch(firstArray, 0, 1, secondArray, 2, 2));
+    }
+    
+    @Test
+    void givenTwoEmptySubArrays_whenMismatch_thenMinusOne() {
+        int[] firstArray = {1};
+        int[] secondArray = {1, 2, 3};
+        assertEquals(-1, Arrays.mismatch(firstArray, 0, 0, secondArray, 2, 2));
+    }
+    
+    @Test
+    void givenToIndexGreaterThanFromIndex_whenMismatch_thenThrowsIllegalArgumentException() {
+        int[] firstArray = {2, 3, 4, 5, 4, 3, 2};
+        int[] secondArray = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+        assertThrows(IllegalArgumentException.class, () -> Arrays.mismatch(firstArray, 4, 2, secondArray, 0, 6));
+        assertThrows(IllegalArgumentException.class, () -> Arrays.mismatch(firstArray, 2, 3, secondArray, 6, 0));
+    }
+    
+    @Test
+    void givenIllegalIndexes_whenMismatch_thenThrowsArrayIndexOutOfBoundsException() {
+        int[] firstArray = {2, 3, 4, 5, 4, 3, 2};
+        int[] secondArray = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+        assertThrows(ArrayIndexOutOfBoundsException.class, () -> Arrays.mismatch(firstArray, -1, 2, secondArray, 0, 6));
+        assertThrows(ArrayIndexOutOfBoundsException.class, () -> Arrays.mismatch(firstArray, 0, 8, secondArray, 0, 6));
+        assertThrows(ArrayIndexOutOfBoundsException.class, () -> Arrays.mismatch(firstArray, 2, 3, secondArray, -5, 0));
+        assertThrows(ArrayIndexOutOfBoundsException.class, () -> Arrays.mismatch(firstArray, 2, 3, secondArray, 11, 12));
+    }
+    
+    @Test
+    void givenTwoStringArraysAndAComparator_whenMismatch_thenIndexOfFirstMismatch() {
+        String[] firstArray = {"one", "two", "three"};
+        String[] secondArray = {"ONE", "TWO", "FOUR"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertEquals(2, Arrays.mismatch(firstArray, secondArray, comparator));
+    }
+    
+    @Test
+    void givenTwoIdenticalStringArraysForTheComparator_whenMismatch_thenMinusOne() {
+        String[] firstArray = {"one", "two", "three"};
+        String[] secondArray = {"ONE", "TWO", "THREE"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertEquals(-1, Arrays.mismatch(firstArray, secondArray, comparator));
+    }
+    
+    @Test
+    void givenFirstStringArrayIsAPrefixOfTheSecondForTheComparator_whenMismatch_thenFirstArrayLength() {
+        String[] firstArray = {"one", "two", "three"};
+        String[] secondArray = {"ONE", "TWO", "THREE", "FOUR", "FIVE"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertEquals(firstArray.length, Arrays.mismatch(firstArray, secondArray, comparator));
+    }
+    
+    @Test
+    void givenNoCommonPrefixForTheComparator_whenMismatch_thenZero() {
+        String[] firstArray = {"one", "two", "three"};
+        String[] secondArray = {"six", "seven", "eight"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertEquals(0, Arrays.mismatch(firstArray, secondArray, comparator));
+    }
+    
+    @Test
+    void givenAtLeastANullArrayOrNullComparator_whenMismatch_thenThrowsNullPointerException() {
+        String[] firstArray = null;
+        String[] secondArray = {"one"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(firstArray, secondArray, comparator));
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(secondArray, firstArray, comparator));
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(secondArray, secondArray, null));
+    }
+    
+    @Test
+    void givenExactlyOneAnEmptyArrayAndAComparator_whenMismatch_thenZero() {
+        String[] firstArray = {};
+        String[] secondArray = {"one"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertEquals(0, Arrays.mismatch(firstArray, secondArray, comparator));
+        assertEquals(0, Arrays.mismatch(secondArray, firstArray, comparator));
+    }
+    
+    @Test
+    void givenTwoEmptyStringArraysForTheComparator_whenMismatch_thenMinusOne() {
+        assertEquals(-1, Arrays.mismatch(new String[] {}, new String[] {}, String.CASE_INSENSITIVE_ORDER));
+    }
+    
+    @Test
+    void givenTwoStringSubarraysAndAComparator_whenMismatch_thenIndexOfFirstMismatch() {
+        String[] firstArray = {"one", "two", "three", "four"};
+        String[] secondArray = {"ZERO", "ONE", "TWO", "FOUR", "EIGHT", "SIXTEEN"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertEquals(2, Arrays.mismatch(firstArray, 0, 4, secondArray, 1, 3, comparator));
+    }
+   
+    @Test
+    void givenTwoIdenticalStringSubArraysForTheComparator_whenMismatch_thenMinusOne() {
+        String[] firstArray = {"zero", "zero", "one", "two"};
+        String[] secondArray = {"zero", "one", "two", "three", "four"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertEquals(-1, Arrays.mismatch(firstArray, 2, 4, secondArray, 1, 3, comparator));
+    }
+    
+    @Test
+    void givenFirstSubArrayIsAPrefixOfTheSecondForTheComparator_whenMismatch_thenFirstArrayLength() {
+        String[] firstArray = {"two", "three", "four", "five", "four", "three", "two"};
+        String[] secondArray = {"ZERO", "ONE", "TWO", "THREE", "FOUR", "FIVE", "EIGHT", "NINE", "TEN"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertEquals(4, Arrays.mismatch(firstArray, 0, 4, secondArray, 2, 9, comparator));
+    }
+    
+    @Test
+    void givenNoCommonPrefixForSubArraysForTheComparator_whenMismatch_thenZero() {
+        String[] firstArray = {"zero", "one"};
+        String[] secondArray = {"TEN", "ELEVEN", "TWELVE"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertEquals(0, Arrays.mismatch(firstArray, 1, 2, secondArray, 1, 2, comparator));
+    }
+    
+    @Test
+    void givenAtLeastANullSubArrayOrNullComparator_whenMismatch_thenThrowsNullPointerException() {
+        String[] firstArray = null;
+        String[] secondArray = {"ONE", "TWO", "THREE", "FOUR", "FIVE"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(firstArray, 0, 1, secondArray, 0, 1, comparator));
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(secondArray, 0, 1, firstArray, 0, 1, comparator));
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(firstArray, 0, 1, firstArray, 0, 1, comparator));
+        assertThrows(NullPointerException.class, () -> Arrays.mismatch(secondArray, 0, 1, secondArray, 0, 1, null));
+    }
+    
+    @Test
+    void givenExactlyOneEmptySubArrayAndAComparator_whenMismatch_thenZero() {
+        String[] firstArray = {"one"};
+        String[] secondArray = {"ONE", "TWO", "THREE"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertEquals(0, Arrays.mismatch(firstArray, 0, 0, secondArray, 0, 2, comparator));
+        assertEquals(0, Arrays.mismatch(firstArray, 0, 1, secondArray, 2, 2, comparator));
+    }
+    
+    @Test
+    void givenTwoEmptySubArraysAndAComparator_whenMismatch_thenMinusOne() {
+        String[] firstArray = {"one"};
+        String[] secondArray = {"ONE", "TWO", "THREE"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertEquals(-1, Arrays.mismatch(firstArray, 0, 0, secondArray, 2, 2, comparator));
+    }
+    
+    @Test
+    void givenToIndexGreaterThanFromIndexAndAComparator_whenMismatch_thenThrowsIllegalArgumentException() {
+        String[] firstArray = {"two", "three", "four", "five", "four", "three", "two"};
+        String[] secondArray = {"ZERO", "ONE", "TWO", "THREE", "FOUR", "FIVE", "EIGHT", "NINE", "TEN"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertThrows(IllegalArgumentException.class, () -> Arrays.mismatch(firstArray, 4, 2, secondArray, 0, 6, comparator));
+        assertThrows(IllegalArgumentException.class, () -> Arrays.mismatch(firstArray, 2, 3, secondArray, 6, 0, comparator));
+    }
+    
+    @Test
+    void givenIllegalIndexesAndAComparator_whenMismatch_thenThrowsArrayIndexOutOfBoundsException() {
+        String[] firstArray = {"two", "three", "four", "five", "four", "three", "two"};
+        String[] secondArray = {"ZERO", "ONE", "TWO", "THREE", "FOUR", "FIVE", "EIGHT", "NINE", "TEN"};
+        Comparator<String> comparator = String.CASE_INSENSITIVE_ORDER;
+        assertThrows(ArrayIndexOutOfBoundsException.class, () -> Arrays.mismatch(firstArray, -1, 2, secondArray, 0, 6, comparator));
+        assertThrows(ArrayIndexOutOfBoundsException.class, () -> Arrays.mismatch(firstArray, 0, 8, secondArray, 0, 6, comparator));
+        assertThrows(ArrayIndexOutOfBoundsException.class, () -> Arrays.mismatch(firstArray, 2, 3, secondArray, -5, 0, comparator));
+        assertThrows(ArrayIndexOutOfBoundsException.class, () -> Arrays.mismatch(firstArray, 2, 3, secondArray, 11, 12, comparator));
+    }
+
+}

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

@@ -7,4 +7,5 @@
 - [Creating Custom Iterator in Java](https://www.baeldung.com/java-creating-custom-iterator)
 - [Difference Between Arrays.sort() and Collections.sort()](https://www.baeldung.com/java-arrays-collections-sort-methods)
 - [Skipping the First Iteration in Java](https://www.baeldung.com/java-skip-first-iteration)
+- [Remove Elements From a Queue Using Loop](https://www.baeldung.com/java-remove-elements-queue)
 - More articles: [[<-- prev]](/core-java-modules/core-java-collections-4)

core-java-modules/core-java-collections-5/src/test/java/com/baeldung/removequeueelements/RemoveQueueElementsUnitTest.java

@@ -12,7 +12,7 @@ public class RemoveQueueElementsUnitTest {
     @Test
     public void givenQueueWithEvenAndOddNumbers_whenRemovingEvenNumbers_thenOddNumbersRemain() {
         Queue<Integer> queue = new LinkedList<>();
-        Queue<Integer> evenElementsQueue = new LinkedList<>();
+        Queue<Integer> oddElementsQueue = new LinkedList<>();
         queue.add(1);
         queue.add(2);
         queue.add(3);
@@ -22,14 +22,14 @@ public class RemoveQueueElementsUnitTest {
         while (queue.peek() != null) {
             int element = queue.remove();
             if (element % 2 != 0) {
-                evenElementsQueue.add(element);
+                oddElementsQueue.add(element);
             }
         }
 
-        assertEquals(3, evenElementsQueue.size());
-        assertTrue(evenElementsQueue.contains(1));
-        assertTrue(evenElementsQueue.contains(3));
-        assertTrue(evenElementsQueue.contains(5));
+        assertEquals(3, oddElementsQueue.size());
+        assertTrue(oddElementsQueue.contains(1));
+        assertTrue(oddElementsQueue.contains(3));
+        assertTrue(oddElementsQueue.contains(5));
     }
 
     @Test

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

@@ -1,2 +1,3 @@
 ## Relevant Articles
 - [Difference Between putIfAbsent() and computeIfAbsent() in Java’s Map](https://www.baeldung.com/java-map-putifabsent-computeifabsent)
+- [How to Write Hashmap to CSV File](https://www.baeldung.com/java-write-hashmap-csv)

core-java-modules/core-java-concurrency-advanced-5/README.md

@@ -0,0 +1,3 @@
+
+### Relevant Articles:
+- [Why wait() Requires Synchronization?](https://www.baeldung.com/java-wait-necessary-synchronization)

core-java-modules/core-java-concurrency-basic-3/README.md

@@ -10,4 +10,5 @@ This module contains articles about basic Java concurrency.
 - [Returning a Value After Finishing Thread’s Job in Java](https://www.baeldung.com/java-return-value-after-thread-finish)
 - [CompletableFuture and ThreadPool in Java](https://www.baeldung.com/java-completablefuture-threadpool)
 - [CompletableFuture allOf().join() vs. CompletableFuture.join()](https://www.baeldung.com/java-completablefuture-allof-join)
+- [Retry Logic with CompletableFuture](https://www.baeldung.com/java-completablefuture-retry-logic)
 - [[<-- Prev]](../core-java-concurrency-basic-2)

core-java-modules/core-java-concurrency-basic-3/src/main/java/com/baeldung/concurrent/completablefuture/retry/RetryCompletableFuture.java

@@ -0,0 +1,63 @@
+package com.baeldung.concurrent.completablefuture.retry;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+public class RetryCompletableFuture {
+    public static <T> CompletableFuture<T> retryTask(Supplier<T> supplier, int maxRetries) {
+        Supplier<T> retryableSupplier = retryFunction(supplier, maxRetries);
+        return CompletableFuture.supplyAsync(retryableSupplier);
+    }
+
+    static <T> Supplier<T> retryFunction(Supplier<T> supplier, int maxRetries) {
+        return () -> {
+            int retries = 0;
+            while (retries < maxRetries) {
+                try {
+                    return supplier.get();
+                } catch (Exception e) {
+                    retries++;
+                }
+            }
+            throw new IllegalStateException(String.format("Task failed after %s attempts", maxRetries));
+        };
+    }
+
+    public static <T> CompletableFuture<T> retryUnsafe(Supplier<T> supplier, int maxRetries) {
+        CompletableFuture<T> cf = CompletableFuture.supplyAsync(supplier);
+        sleep(100l);
+        for (int i = 0; i < maxRetries; i++) {
+            cf = cf.exceptionally(__ -> supplier.get());
+        }
+        return cf;
+    }
+
+    public static <T> CompletableFuture<T> retryNesting(Supplier<T> supplier, int maxRetries) {
+        CompletableFuture<T> cf = CompletableFuture.supplyAsync(supplier);
+        sleep(100);
+        for (int i = 0; i < maxRetries; i++) {
+            cf = cf.thenApply(CompletableFuture::completedFuture)
+              .exceptionally(__ -> CompletableFuture.supplyAsync(supplier))
+              .thenCompose(Function.identity());
+        }
+        return cf;
+    }
+
+    public static <T> CompletableFuture<T> retryExceptionallyAsync(Supplier<T> supplier, int maxRetries) {
+        CompletableFuture<T> cf = CompletableFuture.supplyAsync(supplier);
+        sleep(100);
+        for (int i = 0; i < maxRetries; i++) {
+            cf = cf.exceptionallyAsync(__ -> supplier.get());
+        }
+        return cf;
+    }
+
+    private static void sleep(long millis) {
+        try {
+            Thread.sleep(millis);
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}

core-java-modules/core-java-concurrency-basic-3/src/main/java/com/baeldung/concurrent/completablefuturelist/Application.java

@@ -0,0 +1,100 @@
+package com.baeldung.concurrent.completablefuturelist;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.stream.Collectors;
+
+public class Application {
+
+    ScheduledExecutorService asyncOperationEmulation;
+
+    Application initialize() {
+        asyncOperationEmulation = Executors.newScheduledThreadPool(10);
+        return this;
+    }
+
+    CompletableFuture<String> asyncOperation(String operationId) {
+        CompletableFuture<String> cf = new CompletableFuture<>();
+        asyncOperationEmulation.submit(() -> {
+            // The following lines simulate an exception happening on the 567th operation
+            //  if (operationId.endsWith("567")) {
+            //      cf.completeExceptionally(new Exception("Error on operation " + operationId));
+            //      return;
+            //  }
+            try {
+                Thread.sleep(100);
+                cf.complete(operationId);
+            } catch (InterruptedException e) {
+                System.err.println("Thread interrupted error");
+                cf.completeExceptionally(e);
+            }
+        });
+        return cf;
+    }
+
+    void startNaive() {
+        List<CompletableFuture<String>> futures = new ArrayList<>();
+        for (int i = 1; i <= 1000; i++) {
+            String operationId = "Naive-Operation-" + i;
+            futures.add(asyncOperation(operationId));
+        }
+
+        CompletableFuture<List<String>> aggregate = CompletableFuture.completedFuture(new ArrayList<>());
+        for (CompletableFuture<String> future : futures) {
+            aggregate = aggregate.thenCompose(list -> {
+                try {
+                    list.add(future.get());
+                    return CompletableFuture.completedFuture(list);
+                } catch (Exception e) {
+                    final CompletableFuture<List<String>> excFuture = new CompletableFuture<>();
+                    excFuture.completeExceptionally(e);
+                    return excFuture;
+                }
+            });
+        }
+
+        try {
+            final List<String> results = aggregate.join();
+            System.out.println("Printing first 10 results");
+            for (int i = 0; i < 10; i++) {
+                System.out.println("Finished " + results.get(i));
+            }
+        } finally {
+            close();
+        }
+    }
+
+    void start() {
+        List<CompletableFuture<String>> futures = new ArrayList<>();
+        for (int i = 1; i <= 1000; i++) {
+            String operationId = "Operation-" + i;
+            futures.add(asyncOperation(operationId));
+        }
+        CompletableFuture<?>[] futuresArray = futures.toArray(new CompletableFuture<?>[0]);
+        CompletableFuture<List<String>> listFuture = CompletableFuture.allOf(futuresArray).thenApply(v -> futures.stream().map(CompletableFuture::join).collect(Collectors.toList()));
+        try {
+            final List<String> results = listFuture.join();
+            System.out.println("Printing first 10 results");
+            for (int i = 0; i < 10; i++) {
+                System.out.println("Finished " + results.get(i));
+            }
+        } finally {
+            close();
+        }
+    }
+
+    void close() {
+        asyncOperationEmulation.shutdownNow();
+    }
+
+    public static void main(String[] args) {
+        new Application().initialize()
+        // Switch between .startNaive() and .start() to test both implementations
+        //  .startNaive();
+          .start();
+    }
+
+}

core-java-modules/core-java-concurrency-basic-3/src/test/java/com/baeldung/concurrent/completablefuture/retry/RetryCompletableFutureUnitTest.java

@@ -0,0 +1,120 @@
+package com.baeldung.concurrent.completablefuture.retry;
+
+import static com.baeldung.concurrent.completablefuture.retry.RetryCompletableFuture.retryExceptionallyAsync;
+import static com.baeldung.concurrent.completablefuture.retry.RetryCompletableFuture.retryNesting;
+import static com.baeldung.concurrent.completablefuture.retry.RetryCompletableFuture.retryTask;
+import static com.baeldung.concurrent.completablefuture.retry.RetryCompletableFuture.retryUnsafe;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Supplier;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class RetryCompletableFutureUnitTest {
+    private AtomicInteger retriesCounter = new AtomicInteger(0);
+
+    @BeforeEach
+    void beforeEach() {
+        retriesCounter.set(0);
+    }
+
+    @Test
+    void whenRetryingTask_thenReturnsCorrectlyAfterFourInvocations() {
+        Supplier<Integer> codeToRun = () -> failFourTimesThenReturn(100);
+
+        CompletableFuture<Integer> result = retryTask(codeToRun, 10);
+
+        assertThat(result.join()).isEqualTo(100);
+        assertThat(retriesCounter).hasValue(4);
+    }
+
+    @Test
+    void whenRetryingTask_thenThrowsExceptionAfterThreeInvocations() {
+        Supplier<Integer> codeToRun = () -> failFourTimesThenReturn(100);
+
+        CompletableFuture<Integer> result = retryTask(codeToRun, 3);
+
+        assertThatThrownBy(result::join)
+          .isInstanceOf(CompletionException.class)
+          .hasMessageContaining("IllegalStateException: Task failed after 3 attempts");
+    }
+
+    @Test
+    void whenRetryingExceptionally_thenReturnsCorrectlyAfterFourInvocations() {
+        Supplier<Integer> codeToRun = () -> failFourTimesThenReturn(100);
+
+        CompletableFuture<Integer> result = retryUnsafe(codeToRun, 10);
+
+        assertThat(result.join()).isEqualTo(100);
+        assertThat(retriesCounter).hasValue(4);
+    }
+
+    @Test
+    void whenRetryingExceptionally_thenThrowsExceptionAfterThreeInvocations() {
+        Supplier<Integer> codeToRun = () -> failFourTimesThenReturn(100);
+
+        CompletableFuture<Integer> result = retryUnsafe(codeToRun, 3);
+
+        assertThatThrownBy(result::join)
+          .isInstanceOf(CompletionException.class)
+          .hasMessageContaining("RuntimeException: task failed for 3 time(s)");
+    }
+
+    @Test
+    void whenRetryingExceptionallyAsync_thenReturnsCorrectlyAfterFourInvocations() {
+        Supplier<Integer> codeToRun = () -> failFourTimesThenReturn(100);
+
+        CompletableFuture<Integer> result = retryExceptionallyAsync(codeToRun, 10);
+
+        assertThat(result.join()).isEqualTo(100);
+        assertThat(retriesCounter).hasValue(4);
+    }
+
+    @Test
+    void whenRetryingExceptionallyAsync_thenThrowsExceptionAfterThreeInvocations() {
+        Supplier<Integer> codeToRun = () -> failFourTimesThenReturn(100);
+
+        CompletableFuture<Integer> result = retryExceptionallyAsync(codeToRun, 3);
+
+        assertThatThrownBy(result::join)
+          .isInstanceOf(CompletionException.class)
+          .hasMessageContaining("RuntimeException: task failed for 3 time(s)");
+    }
+
+    @Test
+    void whenRetryingNesting_thenReturnsCorrectlyAfterFourInvocations() {
+        Supplier<Integer> codeToRun = () -> failFourTimesThenReturn(100);
+
+        CompletableFuture<Integer> result = retryNesting(codeToRun, 10);
+
+        assertThat(result.join()).isEqualTo(100);
+        assertThat(retriesCounter).hasValue(4);
+    }
+
+    @Test
+    void whenRetryingNesting_thenThrowsExceptionAfterThreeInvocations() {
+        Supplier<Integer> codeToRun = () -> failFourTimesThenReturn(100);
+
+        CompletableFuture<Integer> result = retryNesting(codeToRun, 3);
+
+        assertThatThrownBy(result::join)
+          .isInstanceOf(CompletionException.class)
+          .hasMessageContaining("RuntimeException: task failed for 3 time(s)");
+    }
+
+    int failFourTimesThenReturn(int returnValue) {
+        int retryNr = retriesCounter.get();
+        System.out.println(String.format("invocation: %s, thread: %s", retryNr, Thread.currentThread().getName()));
+        if (retryNr < 4) {
+            retriesCounter.set(retryNr + 1);
+            throw new RuntimeException(String.format("task failed for %s time(s)", retryNr));
+        }
+        return returnValue;
+    }
+
+}

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

@@ -12,6 +12,7 @@ This module contains articles about Java Concurrency that are also part of an Eb
 - [Guide to the Volatile Keyword in Java](https://www.baeldung.com/java-volatile)
 - [A Guide to the Java ExecutorService](https://www.baeldung.com/java-executor-service-tutorial)
 - [Guide To CompletableFuture](https://www.baeldung.com/java-completablefuture)
+- [How To Manage Timeout for CompletableFuture](https://www.baeldung.com/java-completablefuture-timeout)
 
 ### NOTE:
 

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

@@ -12,6 +12,15 @@
         <version>0.0.1-SNAPSHOT</version>
     </parent>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.wiremock</groupId>
+            <artifactId>wiremock</artifactId>
+            <version>3.1.0</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
     <build>
         <finalName>core-java-concurrency-simple</finalName>
         <resources>

core-java-modules/core-java-concurrency-simple/src/test/java/com/baeldung/concurrent/completablefuture/CompletableFutureTimeoutUnitTest.java

@@ -0,0 +1,182 @@
+package com.baeldung.concurrent.completablefuture;
+
+import com.github.tomakehurst.wiremock.WireMockServer;
+import com.github.tomakehurst.wiremock.client.WireMock;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.util.concurrent.*;
+
+import static com.github.tomakehurst.wiremock.client.WireMock.*;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+class CompletableFutureTimeoutUnitTest {
+    private WireMockServer wireMockServer;
+    private ScheduledExecutorService executorService;
+    private static final int DEFAULT_TIMEOUT = 1000; //1 seconds
+    private static final String DEFAULT_PRODUCT = """
+            {
+              "products": [
+                {
+                  "id": 2,
+                  "title": "iPhone X",
+                  "description": "SIM-Free, Model A19211 6.5-inch Super Retina HD display with OLED technology A12 Bionic chip with ...",
+                  "price": 899,
+                  "discountPercentage": 0.0,
+                  "rating": 4.44,
+                  "stock": 34,
+                  "brand": "Apple",
+                  "category": "smartphones"
+                },
+                {
+                  "id": 3,
+                  "title": "Samsung Universe 9",
+                  "description": "Samsung's new variant which goes beyond Galaxy to the Universe",
+                  "price": 1249,
+                  "discountPercentage": 0.0,
+                  "rating": 4.09,
+                  "stock": 36,
+                  "brand": "Samsung",
+                  "category": "smartphones"
+                }
+              ],
+              "total": 2
+            }""";
+    private static final String PRODUCT_OFFERS = """
+            {
+              "products": [
+                {
+                  "id": 1,
+                  "title": "iPhone 9",
+                  "description": "An apple mobile which is nothing like apple",
+                  "price": 549,
+                  "discountPercentage": 12.96,
+                  "rating": 4.69,
+                  "stock": 94,
+                  "brand": "Apple",
+                  "category": "smartphones"
+                },
+                {
+                  "id": 2,
+                  "title": "iPhone X",
+                  "description": "SIM-Free, Model A19211 6.5-inch Super Retina HD display with OLED technology A12 Bionic chip with ...",
+                  "price": 899,
+                  "discountPercentage": 17.94,
+                  "rating": 4.44,
+                  "stock": 34,
+                  "brand": "Apple",
+                  "category": "smartphones"
+                },
+                {
+                  "id": 3,
+                  "title": "Samsung Universe 9",
+                  "description": "Samsung's new variant which goes beyond Galaxy to the Universe",
+                  "price": 1249,
+                  "discountPercentage": 15.46,
+                  "rating": 4.09,
+                  "stock": 36,
+                  "brand": "Samsung",
+                  "category": "smartphones"
+                },
+                {
+                  "id": 4,
+                  "title": "OPPOF19",
+                  "description": "OPPO F19 is officially announced on April 2021.",
+                  "price": 280,
+                  "discountPercentage": 17.91,
+                  "rating": 4.3,
+                  "stock": 123,
+                  "brand": "OPPO",
+                  "category": "smartphones"
+                },
+                {
+                  "id": 5,
+                  "title": "Huawei P30",
+                  "description": "Huawei’s re-badged P30 Pro New Edition was officially unveiled yesterday in Germany and now the device has made its way to the UK.",
+                  "price": 499,
+                  "discountPercentage": 10.58,
+                  "rating": 4.09,
+                  "stock": 32,
+                  "brand": "Huawei",
+                  "category": "smartphones"
+                }
+              ],
+              "total": 5
+            }""";
+
+    @BeforeAll
+    void setUp() {
+        wireMockServer = new WireMockServer(8080);
+        wireMockServer.start();
+        WireMock.configureFor("localhost", 8080);
+
+        stubFor(get(urlEqualTo("/api/dummy"))
+                .willReturn(aResponse()
+                        .withFixedDelay(5000) // must be > DEFAULT_TIMEOUT for a timeout to occur.
+                        .withBody(PRODUCT_OFFERS)));
+
+        executorService = Executors.newScheduledThreadPool(1);
+    }
+
+    @AfterAll
+    void tearDown() {
+        executorService.shutdown();
+        wireMockServer.stop();
+    }
+
+    private CompletableFuture<String> fetchProductData() {
+        return CompletableFuture.supplyAsync(() -> {
+            try {
+                URL url = new URL("http://localhost:8080/api/dummy");
+                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
+
+                try (BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()))) {
+                    String inputLine;
+                    StringBuffer response = new StringBuffer();
+
+                    while ((inputLine = in.readLine()) != null) {
+                        response.append(inputLine);
+                    }
+
+                    return response.toString();
+                } finally {
+                    connection.disconnect();
+                }
+            } catch (IOException e) {
+                return "";
+            }
+        });
+    }
+
+
+    @Test
+    void whenorTimeout_thenGetThrow() {
+        CompletableFuture<String> productDataFuture = fetchProductData();
+        productDataFuture.orTimeout(DEFAULT_TIMEOUT, TimeUnit.MILLISECONDS);
+        assertThrows(ExecutionException.class, productDataFuture::get);
+    }
+
+    @Test
+    void whencompleteOnTimeout_thenReturnValue() throws ExecutionException, InterruptedException {
+        CompletableFuture<String> productDataFuture = fetchProductData();
+        productDataFuture.completeOnTimeout(DEFAULT_PRODUCT, DEFAULT_TIMEOUT, TimeUnit.MILLISECONDS);
+        assertEquals(DEFAULT_PRODUCT, productDataFuture.get());
+    }
+
+    @Test
+    void whencompleteExceptionally_thenGetThrow() {
+        CompletableFuture<String> productDataFuture = fetchProductData();
+        executorService.schedule(() -> productDataFuture
+                .completeExceptionally(new TimeoutException("Timeout occurred")), DEFAULT_TIMEOUT, TimeUnit.MILLISECONDS);
+        assertThrows(ExecutionException.class, productDataFuture::get);
+    }
+}

core-java-modules/core-java-date-operations-3/src/test/java/com/baeldung/firstdaymonth/FirstDayOfMonthUnitTest.java

@@ -0,0 +1,61 @@
+package com.baeldung.firstdaymonth;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.time.LocalDate;
+import java.time.YearMonth;
+import java.time.temporal.TemporalAdjusters;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.GregorianCalendar;
+
+import org.junit.jupiter.api.Test;
+
+public class FirstDayOfMonthUnitTest {
+
+    @Test
+    void givenMonth_whenUsingCalendar_thenReturnFirstDay() {
+        Date currentDate = new GregorianCalendar(2023, Calendar.NOVEMBER, 23).getTime();
+        Date expectedDate = new GregorianCalendar(2023, Calendar.NOVEMBER, 1).getTime();
+
+        Calendar cal = Calendar.getInstance();
+        cal.setTime(currentDate);
+        cal.set(Calendar.DAY_OF_MONTH, 1);
+
+        assertEquals(expectedDate, cal.getTime());
+    }
+
+    @Test
+    void givenMonth_whenUsingLocalDate_thenReturnFirstDay() {
+        LocalDate currentDate = LocalDate.of(2023, 9, 6);
+        LocalDate expectedDate = LocalDate.of(2023, 9, 1);
+
+        assertEquals(expectedDate, currentDate.withDayOfMonth(1));
+    }
+
+    @Test
+    void givenMonth_whenUsingTemporalAdjusters_thenReturnFirstDay() {
+        LocalDate currentDate = LocalDate.of(2023, 7, 19);
+        LocalDate expectedDate = LocalDate.of(2023, 7, 1);
+
+        assertEquals(expectedDate, currentDate.with(TemporalAdjusters.firstDayOfMonth()));
+    }
+
+    @Test
+    void givenMonth_whenUsingYearMonth_thenReturnFirstDay() {
+        YearMonth currentDate = YearMonth.of(2023, 4);
+        LocalDate expectedDate = LocalDate.of(2023, 4, 1);
+
+        assertEquals(expectedDate, currentDate.atDay(1));
+    }
+
+    @Test
+    void givenMonth_whenUsingJodaTime_thenReturnFirstDay() {
+        org.joda.time.LocalDate currentDate = org.joda.time.LocalDate.parse("2023-5-10");
+        org.joda.time.LocalDate expectedDate = org.joda.time.LocalDate.parse("2023-5-1");
+
+        assertEquals(expectedDate, currentDate.dayOfMonth()
+          .withMinimumValue());
+    }
+
+}

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

@@ -35,6 +35,21 @@
             <artifactId>simplemagic</artifactId>
             <version>${simplemagic.version}</version>
         </dependency>
+        <dependency>
+            <groupId>commons-io</groupId>
+            <artifactId>commons-io</artifactId>
+            <version>${commons-io.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -62,5 +77,6 @@
         <jmime-magic.version>0.1.5</jmime-magic.version>
         <jodd-util.version>6.2.1</jodd-util.version>
         <simplemagic.version>1.17</simplemagic.version>
+        <jmh.version>1.37</jmh.version>
     </properties>
 </project>

core-java-modules/core-java-io-5/src/main/java/com/baeldung/zip/ZipBenchmark.java

@@ -0,0 +1,112 @@
+package com.baeldung.zip;
+
+import java.io.*;
+import java.util.concurrent.TimeUnit;
+import java.util.*;
+import java.util.zip.*;
+
+import org.openjdk.jmh.annotations.*;
+import org.openjdk.jmh.infra.Blackhole;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+@State(Scope.Benchmark)
+@BenchmarkMode(Mode.AverageTime)
+@Warmup(iterations = 1, time = 2, timeUnit = TimeUnit.SECONDS)
+@Measurement(iterations = 3, time = 1, timeUnit = TimeUnit.SECONDS)
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+@Fork(value = 1)
+public class ZipBenchmark {
+
+    public static final int NUM_OF_FILES = 10;
+    public static final int DATA_SIZE = 204800;
+
+    @State(Scope.Thread)
+    public static class SourceState {
+
+        public File compressedFile;
+
+        @Setup(Level.Trial)
+        public void setup() throws IOException {
+            ZipSampleFileStore sampleFileStore = new ZipSampleFileStore(NUM_OF_FILES, DATA_SIZE);
+            compressedFile = sampleFileStore.getFile();
+        }
+
+        @TearDown(Level.Trial)
+        public void cleanup() {
+            if (compressedFile.exists()) {
+                compressedFile.delete();
+            }
+        }
+    }
+
+    @Benchmark
+    public static void readAllEntriesByZipFile(SourceState sourceState, Blackhole blackhole) throws IOException {
+
+        try (ZipFile zipFile = new ZipFile(sourceState.compressedFile)) {
+            Enumeration<? extends ZipEntry> zipEntries = zipFile.entries();
+            while (zipEntries.hasMoreElements())  {
+                ZipEntry zipEntry = zipEntries.nextElement();
+                try (InputStream inputStream = new BufferedInputStream(zipFile.getInputStream(zipEntry))) {
+                    blackhole.consume(ZipSampleFileStore.getString(inputStream));
+                }
+            }
+        }
+    }
+
+    @Benchmark
+    public static void readAllEntriesByZipInputStream(SourceState sourceState, Blackhole blackhole) throws IOException {
+
+        try (
+            BufferedInputStream bis = new BufferedInputStream(new FileInputStream(sourceState.compressedFile));
+            ZipInputStream zipInputStream = new ZipInputStream(bis)
+        ) {
+            ZipEntry entry;
+            while ((entry = zipInputStream.getNextEntry()) != null) {
+                blackhole.consume(ZipSampleFileStore.getString(zipInputStream));
+            }
+        }
+    }
+
+    @Benchmark
+    public static void readLastEntryByZipFile(SourceState sourceState, Blackhole blackhole) throws IOException {
+
+        try (ZipFile zipFile = new ZipFile(sourceState.compressedFile)) {
+           ZipEntry zipEntry = zipFile.getEntry(getLastEntryName());
+            try (InputStream inputStream = new BufferedInputStream(zipFile.getInputStream(zipEntry))) {
+                blackhole.consume(ZipSampleFileStore.getString(inputStream));
+            }
+        }
+    }
+
+    @Benchmark
+    public static void readLastEntryByZipInputStream(SourceState sourceState, Blackhole blackhole) throws IOException {
+
+        try (
+            BufferedInputStream bis = new BufferedInputStream(new FileInputStream(sourceState.compressedFile));
+            ZipInputStream zipInputStream = new ZipInputStream(bis)
+        ) {
+            ZipEntry entry;
+            while ((entry = zipInputStream.getNextEntry()) != null) {
+                if (Objects.equals(entry.getName(), getLastEntryName())){
+                    blackhole.consume(ZipSampleFileStore.getString(zipInputStream));
+                }
+            }
+        }
+    }
+
+    private static String getLastEntryName() {
+        return String.format(ZipSampleFileStore.ENTRY_NAME_PATTERN, NUM_OF_FILES);
+    }
+
+    public static void main(String[] args) throws Exception {
+        Options options = new OptionsBuilder()
+          .include(ZipBenchmark.class.getSimpleName()).threads(1)
+          .shouldFailOnError(true)
+          .shouldDoGC(true)
+          .jvmArgs("-server").build();
+        new Runner(options).run();
+    }
+
+}

core-java-modules/core-java-io-5/src/main/java/com/baeldung/zip/ZipSampleFileStore.java

@@ -0,0 +1,70 @@
+package com.baeldung.zip;
+
+import java.io.*;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import java.util.*;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipOutputStream;
+
+import org.apache.commons.io.IOUtils;
+
+public class ZipSampleFileStore {
+
+    public static final String ENTRY_NAME_PATTERN = "str-data-%s.txt";
+    private static final Charset DEFAULT_ENCODING = StandardCharsets.UTF_8;
+
+    private final File file;
+    private final List<String> dataList;
+
+    public ZipSampleFileStore(int numOfFiles, int fileSize) throws IOException {
+
+        dataList = new ArrayList<>(numOfFiles);
+        file = File.createTempFile("zip-sample", "");
+
+        try (ZipOutputStream zos = new ZipOutputStream(new FileOutputStream(file))) {
+
+            for (int idx=0; idx<=numOfFiles; idx++) {
+
+                byte[] data = createRandomStringInByte(fileSize);
+                dataList.add(new String(data, DEFAULT_ENCODING));
+
+                ZipEntry entry = new ZipEntry(String.format(ENTRY_NAME_PATTERN, idx));
+                zos.putNextEntry(entry);
+                zos.write(data);
+                zos.closeEntry();
+            }
+        }
+    }
+
+    public static byte[] createRandomStringInByte(int size) {
+        Random random = new Random();
+        byte[] data = new byte[size];
+        for (int n = 0; n < data.length; n++) {
+            char randomChar;
+            int choice = random.nextInt(2); // 0 for uppercase, 1 for lowercase
+            if (choice == 0) {
+                randomChar = (char) ('A' + random.nextInt(26)); // 'A' to 'Z'
+            } else {
+                randomChar = (char) ('a' + random.nextInt(26)); // 'a' to 'z'
+            }
+            data[n] = (byte) randomChar;
+        }
+        return data;
+    }
+
+    public File getFile() {
+        return file;
+    }
+
+    public List<String> getDataList() {
+        return dataList;
+    }
+
+    public static String getString(InputStream inputStream) throws IOException {
+        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
+        IOUtils.copy(inputStream, byteArrayOutputStream);
+        return byteArrayOutputStream.toString(DEFAULT_ENCODING);
+    }
+
+}

core-java-modules/core-java-io-5/src/test/java/com/baeldung/zip/ZipUnitTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.zip;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.*;
+import java.util.*;
+import java.util.zip.*;
+
+import org.junit.*;
+
+public class ZipUnitTest {
+
+    private static File compressedFile;
+    private static List<String> dataList = new ArrayList<>();
+
+    @BeforeClass
+    public static void prepareData() throws IOException {
+        ZipSampleFileStore sampleFileStore = new ZipSampleFileStore(ZipBenchmark.NUM_OF_FILES, ZipBenchmark.DATA_SIZE);
+        compressedFile = sampleFileStore.getFile();
+        dataList = sampleFileStore.getDataList();
+    }
+
+    @Test
+    public void whenCreateZipFile_thenCompressedSizeShouldBeLessThanOriginal() throws IOException {
+        byte[] data = ZipSampleFileStore.createRandomStringInByte(10240);
+        File file = File.createTempFile("zip-temp", "");
+
+        try (
+            BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(file));
+            ZipOutputStream zos = new ZipOutputStream(bos)
+        ) {
+            ZipEntry zipEntry = new ZipEntry("zip-entry.txt");
+            zos.putNextEntry(zipEntry);
+            zos.write(data);
+            zos.closeEntry();
+
+            assertThat(file.length()).isLessThan(data.length);
+        }
+        finally {
+            file.delete();
+        }
+    }
+
+    @Test
+    public void whenReadAllEntriesViaZipFile_thenDataIsEqualtoTheSource() throws IOException {
+
+        try (ZipFile zipFile = new ZipFile(compressedFile)) {
+            Enumeration<? extends ZipEntry> entries = zipFile.entries();
+            List<? extends ZipEntry> entryList = Collections.list(entries);
+
+            for (int idx=0; idx<entryList.size(); idx++) {
+                ZipEntry zipEntry = entryList.get(idx);
+                try (InputStream inputStream = zipFile.getInputStream(zipEntry)) {
+                    String actual = ZipSampleFileStore.getString(inputStream);
+                    assertThat(actual).as("Data for ZIP entry: " + zipEntry.getName()).isEqualTo(dataList.get(idx));
+                }
+            }
+        }
+    }
+
+    @Test
+    public void whenReadAllEntriesViaZipInputStream_thenDataIsEqualtoTheSource() throws IOException {
+        int idx = 0;
+        try (
+            BufferedInputStream bis = new BufferedInputStream(new FileInputStream(compressedFile));
+            ZipInputStream zipInputStream = new ZipInputStream(bis)
+        ) {
+            ZipEntry zipEntry;
+            while ((zipEntry = zipInputStream.getNextEntry()) != null) {
+                String actual = ZipSampleFileStore.getString(zipInputStream);
+                assertThat(actual).as("Data for ZIP entry: " + zipEntry.getName()).isEqualTo(dataList.get(idx++));
+            }
+        }
+    }
+
+    @AfterClass
+    public static void cleanup() {
+        if (compressedFile.exists()) {
+            compressedFile.delete();
+        }
+    }
+
+}

core-java-modules/core-java-io-apis-2/alabama.txt

@@ -0,0 +1,2 @@
+I'm going to Alabama
+Alabama is a state in the US

core-java-modules/core-java-io-apis-2/dream.txt

@@ -0,0 +1 @@
+Dreams from My Father by Barack Obama

core-java-modules/core-java-io-apis-2/potter.txt

@@ -0,0 +1 @@
+Harry Potter and the Chamber of Secrets

core-java-modules/core-java-io-apis-2/src/test/java/com/baeldung/printwritervsfilewriter/PrintWriterVsFilePrinterUnitTest.java

@@ -0,0 +1,64 @@
+package com.baeldung.printwritervsfilewriter;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileReader;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+public class PrintWriterVsFilePrinterUnitTest {
+
+    @Test
+    public void whenWritingToTextFileUsingFileWriter_thenTextMatches() throws IOException {
+        String result = "Harry Potter and the Chamber of Secrets";
+
+        File file = new File("potter.txt");
+        try (FileWriter fw = new FileWriter(file);) {
+            fw.write("Harry Potter and the Chamber of Secrets");
+        }
+
+        try (BufferedReader reader = new BufferedReader(new FileReader(file));) {
+            String actualData = reader.readLine();
+            assertEquals(result, actualData);
+        }
+    }
+
+    @Test
+    public void whenWritingToTextFileUsingPrintWriterPrintf_thenTextMatches() throws IOException {
+        String result = "Dreams from My Father by Barack Obama";
+        File file = new File("dream.txt");
+        try (PrintWriter pw = new PrintWriter(file);) {
+            String author = "Barack Obama";
+            pw.printf("Dreams from My Father by %s", author);
+            assertTrue(!pw.checkError());
+        }
+
+        try (BufferedReader reader = new BufferedReader(new FileReader(file));) {
+            String actualData = reader.readLine();
+            assertEquals(result, actualData);
+        }
+    }
+
+    @Test
+    public void whenWritingToTextFileUsingPrintWriterPrintln_thenTextMatches() throws IOException {
+        String result = "I'm going to Alabama\nAlabama is a state in the US\n";
+        try (PrintWriter pw = new PrintWriter("alabama.txt");) {
+            pw.println("I'm going to Alabama");
+            pw.println("Alabama is a state in the US");
+        }
+        Path path = Paths.get("alabama.txt");
+        String actualData = new String(Files.readAllBytes(path));
+        assertEquals(result, actualData);
+    }
+
+}

core-java-modules/core-java-numbers-6/src/test/java/com/baeldung/truncatedouble/TruncateDoubleUnitTest.java

@@ -0,0 +1,73 @@
+package com.baeldung.truncatedouble;
+
+import static org.junit.Assert.assertEquals;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+import java.text.DecimalFormat;
+import java.text.NumberFormat;
+
+import org.junit.Test;
+
+public class TruncateDoubleUnitTest {
+
+    @Test
+    public void givenADouble_whenUsingDecimalFormat_truncateToTwoDecimalPlaces() {
+        DecimalFormat df = new DecimalFormat("#.##");
+        df.setRoundingMode(RoundingMode.DOWN);
+
+        double value = 1.55555555;
+        String truncated = df.format(value);
+        assertEquals("1.55", truncated);
+
+        double negativeValue = -1.55555555;
+        String negativeTruncated = df.format(negativeValue);
+        assertEquals("-1.55", negativeTruncated);
+    }
+
+    @Test
+    public void givenADouble_whenUsingNumberFormat_truncateToTwoDecimalPlaces() {
+        NumberFormat nf = NumberFormat.getNumberInstance();
+        nf.setMaximumFractionDigits(2);
+        nf.setRoundingMode(RoundingMode.DOWN);
+
+        double value = 1.55555555;
+        String truncated = nf.format(value);
+        assertEquals("1.55", truncated);
+
+        double negativeValue = -1.55555555;
+        String negativeTruncated = nf.format(negativeValue);
+        assertEquals("-1.55", negativeTruncated);
+    }
+
+    @Test
+    public void givenADouble_whenUsingBigDecimal_truncateToTwoDecimalPlaces() {
+        BigDecimal positive = new BigDecimal(2.555555).setScale(2, RoundingMode.DOWN);
+        BigDecimal negative = new BigDecimal(-2.555555).setScale(2, RoundingMode.DOWN);
+        assertEquals("2.55", positive.toString());
+        assertEquals("-2.55", negative.toString());
+    }
+
+    @Test
+    public void givenADouble_whenUsingMath_truncateToTwoDecimalPlaces() {
+        double positive = 1.55555555;
+        double truncated = Math.floor(positive * 100) / 100;
+        assertEquals("1.55", String.valueOf(truncated));
+
+        double negative = -1.55555555;
+        double negativeTruncated = Math.ceil(negative * 100) / 100;
+        assertEquals("-1.55", String.valueOf(negativeTruncated));
+    }
+
+    @Test
+    public void givenADouble_whenUsingStringFormat_truncateToTwoDecimalPlaces() {
+        double positive = 1.55555555;
+        String truncated = String.format("%.2f", positive);
+        assertEquals("1.56", truncated);
+
+        double negative = -1.55555555;
+        String negativeTruncated = String.format("%.2f", negative);
+        assertEquals("-1.56", negativeTruncated);
+    }
+
+}

core-java-modules/core-java-numbers-conversions/src/test/java/com/baeldung/floatdoubleconversions/FloatDoubleConversionsTest.java

@@ -7,23 +7,27 @@ public class FloatDoubleConversionsTest {
 
     @Test
     public void whenDoubleType_thenFloatTypeSuccess(){
-        double interestRatesYearly = 13.333333333333334;
+        double interestRatesYearly = 13.333333333333333;
         float interest = (float) interestRatesYearly;
-        Assert.assertEquals(13.333333f, interest, 0.000004f);
+        System.out.println(interest); //13.333333
+        Assert.assertEquals(13.333333f, interest, 0.000001f);
 
-        Double monthlyRates = 2.111111111111112;
+        Double monthlyRates = 2.111111111111111;
         float rates = monthlyRates.floatValue();
-        Assert.assertEquals(2.1111112f, rates, 0.00000013);
+        System.out.println(rates); //2.1111112
+        Assert.assertEquals(2.1111111f, rates, 0.0000001f);
     }
     @Test
     public void whenFloatType_thenDoubleTypeSuccess(){
         float gradeAverage =2.05f;
         double average = gradeAverage;
-        Assert.assertEquals(2.05, average, 0.06);
+        System.out.println(average); //2.049999952316284
+        Assert.assertEquals(2.05, average, 0.01);
 
-        Float monthlyRates = 2.1111112f;
+        Float monthlyRates = 2.1111111f;
         Double rates = monthlyRates.doubleValue();
-        Assert.assertEquals(2.11111112, rates, 0.0000002);//true
+        System.out.println(rates); //2.1111111640930176
+        Assert.assertEquals(2.11111111, rates, 0.0000001);//true
     }
 
 }

core-java-modules/core-java-regex-2/src/main/java/com/baeldung/alphanumeric/AlphanumericPerformanceBenchmark.java

@@ -85,7 +85,7 @@ public class AlphanumericPerformanceBenchmark {
 
     public boolean isAlphanumeric(final int codePoint) {
         return (codePoint >= 65 && codePoint <= 90) ||
-               (codePoint >= 97 && codePoint <= 172) ||
+               (codePoint >= 97 && codePoint <= 122) ||
                (codePoint >= 48 && codePoint <= 57);
     }
 }

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

@@ -4,3 +4,4 @@
 - [Aggregate Runtime Exceptions in Java Streams](https://www.baeldung.com/java-streams-aggregate-exceptions)
 - [Streams vs. Loops in Java](https://www.baeldung.com/java-streams-vs-loops)
 - [Partition a Stream in Java](https://www.baeldung.com/java-partition-stream)
+- [Taking Every N-th Element from Finite and Infinite Streams in Java](https://www.baeldung.com/java-nth-element-finite-infinite-streams)

core-java-modules/core-java-string-algorithms-3/README.md

@@ -13,3 +13,4 @@ This module contains articles about string-related algorithms.
 - [Find the Most Frequent Characters in a String](https://www.baeldung.com/java-string-find-most-frequent-characters)
 - [Checking If a String Is a Repeated Substring](https://www.baeldung.com/java-repeated-substring)
 - [Check if Letter Is Emoji With Java](https://www.baeldung.com/java-check-letter-emoji)
+- [Wrapping a String After a Number of Characters Word-Wise](https://www.baeldung.com/java-wrap-string-number-characters-word-wise)

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

@@ -3,3 +3,5 @@
 - [Convert String to Int Using Encapsulation](https://www.baeldung.com/java-encapsulation-convert-string-to-int)
 - [HashMap with Multiple Values for the Same Key](https://www.baeldung.com/java-hashmap-multiple-values-per-key)
 - [Split Java String Into Key-Value Pairs](https://www.baeldung.com/java-split-string-map)
+- [How to Center Text Output in Java](https://www.baeldung.com/java-center-text-output)
+- [How to Convert an Object to String](https://www.baeldung.com/java-object-string-representation)

core-java-modules/core-java-string-operations-2/pom.xml

@@ -54,6 +54,11 @@
             <artifactId>commons-codec</artifactId>
             <version>${commons-codec.version}</version>
         </dependency>
+        <dependency> 
+            <groupId>org.springframework</groupId> 
+            <artifactId>spring-core</artifactId> 
+            <version>${spring-core.version}</version> 
+        </dependency>
     </dependencies>
 
     <build>
@@ -95,6 +100,7 @@
         <javax.el-api.version>3.0.0</javax.el-api.version>
         <javax.el.version>2.2.6</javax.el.version>
         <commons-codec.version>1.14</commons-codec.version>
+        <spring-core.version>5.3.0</spring-core.version>
     </properties>
 
 </project>

core-java-modules/core-java-string-operations-2/src/test/java/com/baeldung/emptystrings/EmptyStringsUnitTest.java

@@ -3,6 +3,7 @@ package com.baeldung.emptystrings;
 import com.google.common.base.Strings;
 import org.apache.commons.lang3.StringUtils;
 import org.junit.Test;
+import org.springframework.util.ObjectUtils;
 
 import javax.validation.ConstraintViolation;
 import javax.validation.Validation;
@@ -109,6 +110,24 @@ public class EmptyStringsUnitTest {
         assertFalse(Strings.isNullOrEmpty(blankString));
     }
 
+    /*
+     * Spring Core ObjectUtils
+     */
+    @Test
+    public void givenSomeEmptyString_thenObjectUtilsIsEmptyReturnsTrue() {
+        assertTrue(ObjectUtils.isEmpty(emptyString));
+    }
+
+    @Test
+    public void givenSomeNonEmptyString_thenObjectUtilsIsEmptyReturnsFalse() {
+        assertFalse(ObjectUtils.isEmpty(nonEmptyString));
+    }
+
+    @Test
+    public void givenSomeBlankString_thenObjectUtilsIsEmptyReturnsFalse() {
+        assertFalse(ObjectUtils.isEmpty(blankString));
+    }
+
     /*
      * Bean Validation
      */

core-java-modules/core-java-string-operations-6/README.md

@@ -11,4 +11,4 @@
 - [Check if a String Has All Unique Characters in Java](https://www.baeldung.com/java-check-string-all-unique-chars)
 - [Performance Comparison Between Different Java String Concatenation Methods](https://www.baeldung.com/java-string-concatenation-methods)
 - [Replacing Single Quote with \’ in Java String](https://www.baeldung.com/java-replacing-single-quote-string)
-
+- [Check if a String Contains a Number Value in Java](https://www.baeldung.com/java-string-number-presence)

core-java-modules/core-java-string-operations-7/README.md

@@ -1,2 +1,4 @@
 
 ### Relevant Articles:
+- [How to Center Text Output in Java](https://www.baeldung.com/java-center-text-output)
+- [Capitalize the First Letter of Each Word in a String](https://www.baeldung.com/java-string-initial-capital-letter-every-word)

core-java-modules/core-java-string-operations-7/pom.xml

@@ -1,72 +1,72 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0"
-    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <modelVersion>4.0.0</modelVersion>
-    <artifactId>core-java-string-operations-7</artifactId>
-    <name>core-java-string-operations-7</name>
-    <packaging>jar</packaging>
-
-    <parent>
-        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>core-java-modules</artifactId>
-        <version>0.0.1-SNAPSHOT</version>
-    </parent>
-
-    <dependencies>
-        <dependency>
-            <groupId>org.apache.commons</groupId>
-            <artifactId>commons-lang3</artifactId>
-            <version>${apache.commons.lang3.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.apache.commons</groupId>
-            <artifactId>commons-text</artifactId>
-            <version>${commons-text.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.liquibase</groupId>
-            <artifactId>liquibase-core</artifactId>
-            <version>4.9.1</version>
-            <scope>test</scope>
-        </dependency>
-        <dependency>
-            <groupId>org.junit.jupiter</groupId>
-            <artifactId>junit-jupiter</artifactId>
-            <version>5.8.1</version>
-            <scope>test</scope>
-        </dependency>
-        <dependency>
-            <groupId>org.liquibase</groupId>
-            <artifactId>liquibase-core</artifactId>
-            <version>4.9.1</version>
-            <scope>test</scope>
-        </dependency>
-        <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
-            <version>4.13.2</version>
-        </dependency>
-    </dependencies>
-
-    <build>
-        <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <configuration>
-                    <source>${maven.compiler.source}</source>
-                    <target>${maven.compiler.target}</target>
-                </configuration>
-            </plugin>
-        </plugins>
-    </build>
-
-    <properties>
-        <maven.compiler.source>11</maven.compiler.source>
-        <maven.compiler.target>11</maven.compiler.target>
-        <apache.commons.lang3.version>3.12.0</apache.commons.lang3.version>
-        <commons-text.version>1.10.0</commons-text.version>
-    </properties>
-
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-string-operations-7</artifactId>
+    <name>core-java-string-operations-7</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${apache.commons.lang3.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-text</artifactId>
+            <version>${commons-text.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.liquibase</groupId>
+            <artifactId>liquibase-core</artifactId>
+            <version>4.9.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>5.8.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.liquibase</groupId>
+            <artifactId>liquibase-core</artifactId>
+            <version>4.9.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.13.2</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+        <apache.commons.lang3.version>3.13.0</apache.commons.lang3.version>
+        <commons-text.version>1.10.0</commons-text.version>
+    </properties>
+
 </project>

core-java-modules/core-java-string-operations-7/src/main/java/com/baeldung/capitalizefirstcharactereachword/CapitalizeFirstCharacterEachWordUtils.java

@@ -0,0 +1,40 @@
+package com.baeldung.capitalizefirstcharactereachword;
+
+import java.util.Arrays;
+import java.util.stream.Collectors;
+
+import org.apache.commons.lang3.StringUtils;
+
+class CapitalizeFirstCharacterEachWordUtils {
+
+    static String usingCharacterToUpperCaseMethod(String input) {
+        if (input == null || input.isEmpty()) {
+            return null;
+        }
+
+        return Arrays.stream(input.split("\\s+"))
+          .map(word -> Character.toUpperCase(word.charAt(0)) + word.substring(1))
+          .collect(Collectors.joining(" "));
+    }
+
+    static String usingStringToUpperCaseMethod(String input) {
+        if (input == null || input.isEmpty()) {
+            return null;
+        }
+
+        return Arrays.stream(input.split("\\s+"))
+          .map(word -> word.substring(0, 1).toUpperCase() + word.substring(1))
+          .collect(Collectors.joining(" "));
+    }
+
+    static String usingStringUtilsClass(String input) {
+        if (input == null || input.isEmpty()) {
+            return null;
+        }
+
+        return Arrays.stream(input.split("\\s+"))
+          .map(StringUtils::capitalize)
+          .collect(Collectors.joining(" "));
+    }
+
+}

core-java-modules/core-java-string-operations-7/src/main/java/com/baeldung/strcontainsnumber/StrContainsNumberUtils.java

@@ -0,0 +1,77 @@
+package com.baeldung.strcontainsnumber;
+
+import java.util.regex.Pattern;
+
+import org.apache.commons.lang3.StringUtils;
+
+import com.google.common.base.CharMatcher;
+
+public class StrContainsNumberUtils {
+
+    static boolean checkUsingMatchesMethod(String input) {
+        if (input == null || input.isEmpty()) {
+            return false;
+        }
+
+        return input.matches(".*\\d.*");
+    }
+
+    static boolean checkUsingPatternClass(String input) {
+        if (input == null || input.isEmpty()) {
+            return false;
+        }
+
+        return Pattern.compile(".*\\d.*")
+          .matcher(input)
+          .matches();
+    }
+
+    static boolean checkUsingReplaceAllMethod(String input) {
+        if (input == null || input.isEmpty()) {
+            return false;
+        }
+
+        String result = input.replaceAll("\\d", "");
+        return result.length() != input.length();
+    }
+
+    static boolean checkUsingIsDigitMethod(String input) {
+        if (input == null || input.isEmpty()) {
+            return false;
+        }
+
+        for (char c : input.toCharArray()) {
+            if (Character.isDigit(c)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    static boolean checkUsingStreamApi(String input) {
+        if (input == null || input.isEmpty()) {
+            return false;
+        }
+
+        return input.chars()
+          .anyMatch(Character::isDigit);
+    }
+
+    static boolean checkUsingApacheCommonsLang(String input) {
+        String result = StringUtils.getDigits(input);
+        return result != null && !result.isEmpty();
+    }
+
+    static boolean checkUsingGuava(String input) {
+        if (input == null || input.isEmpty()) {
+            return false;
+        }
+
+        String result = CharMatcher.forPredicate(Character::isDigit)
+          .retainFrom(input);
+
+        return !result.isEmpty();
+    }
+
+}

core-java-modules/core-java-string-operations-7/src/main/java/com/baeldung/unicode/UnicodeLetterChecker.java

@@ -0,0 +1,30 @@
+package com.baeldung.unicode;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import org.apache.commons.lang3.StringUtils;
+
+public class UnicodeLetterChecker {
+    public boolean characterClassCheck(String input) {
+        for (char c : input.toCharArray()) {
+            if (!Character.isLetter(c)) {
+                return false;
+            }
+        }
+        return true;
+    }
+    
+    public boolean regexCheck(String input) {
+        Pattern pattern = Pattern.compile("^\\p{L}+$");
+        Matcher matcher = pattern.matcher(input);
+        return matcher.matches();
+    }
+    
+    public boolean isAlphaCheck(String input) {
+        return StringUtils.isAlpha(input);
+    }
+    
+    public boolean StreamsCheck(String input) {
+        return input.codePoints().allMatch(Character::isLetter);
+    }
+}

core-java-modules/core-java-string-operations-7/src/test/java/com/baeldung/capitalizefirstcharactereachword/CapitalizeFirstCharacterEachWordUtilsUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.capitalizefirstcharactereachword;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.apache.commons.text.WordUtils;
+import org.junit.jupiter.api.Test;
+
+class CapitalizeFirstCharacterEachWordUtilsUnitTest {
+
+    @Test
+    void givenString_whenUsingCharacterToUpperCaseMethod_thenCapitalizeFirstCharacter() {
+        String input = "hello baeldung visitors";
+
+        assertEquals("Hello Baeldung Visitors", CapitalizeFirstCharacterEachWordUtils.usingCharacterToUpperCaseMethod(input));
+    }
+
+    @Test
+    void givenString_whenUsingSubstringMethod_thenCapitalizeFirstCharacter() {
+        String input = "Hi, my name is azhrioun";
+
+        assertEquals("Hi, My Name Is Azhrioun", CapitalizeFirstCharacterEachWordUtils.usingStringToUpperCaseMethod(input));
+    }
+
+    @Test
+    void givenString_whenUsingStringUtilsClass_thenCapitalizeFirstCharacter() {
+        String input = "life is short the world is wide";
+
+        assertEquals("Life Is Short The World Is Wide", CapitalizeFirstCharacterEachWordUtils.usingStringUtilsClass(input));
+    }
+
+    @Test
+    void givenString_whenUsingWordUtilsClass_thenCapitalizeFirstCharacter() {
+        String input = "smile sunshine is good for your teeth";
+
+        assertEquals("Smile Sunshine Is Good For Your Teeth", WordUtils.capitalizeFully(input));
+    }
+
+}

core-java-modules/core-java-string-operations-7/src/test/java/com/baeldung/strcontainsnumber/StrContainsNumberUtilsUnitTest.java

@@ -0,0 +1,69 @@
+package com.baeldung.strcontainsnumber;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+import org.junit.Test;
+
+public class StrContainsNumberUtilsUnitTest {
+
+    private static final String INPUT_WITH_NUMBERS = "We hope 2024 will be great";
+    private static final String INPUT_WITHOUT_NUMBERS = "Hello world";
+
+    @Test
+    public void givenInputString_whenUsingMatchesMethod_ThenCheck() {
+        assertTrue(StrContainsNumberUtils.checkUsingMatchesMethod(INPUT_WITH_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingMatchesMethod(INPUT_WITHOUT_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingMatchesMethod(""));
+        assertFalse(StrContainsNumberUtils.checkUsingMatchesMethod(null));
+    }
+
+    @Test
+    public void givenInputString_whenUsingPatternClass_ThenCheck() {
+        assertTrue(StrContainsNumberUtils.checkUsingPatternClass(INPUT_WITH_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingPatternClass(INPUT_WITHOUT_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingPatternClass(""));
+        assertFalse(StrContainsNumberUtils.checkUsingPatternClass(null));
+    }
+
+    @Test
+    public void givenInputString_whenUsingReplaceAllMethod_ThenCheck() {
+        assertTrue(StrContainsNumberUtils.checkUsingReplaceAllMethod(INPUT_WITH_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingReplaceAllMethod(INPUT_WITHOUT_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingReplaceAllMethod(""));
+        assertFalse(StrContainsNumberUtils.checkUsingReplaceAllMethod(null));
+    }
+
+    @Test
+    public void givenInputString_whenUsingIsDigitMethod_ThenCheck() {
+        assertTrue(StrContainsNumberUtils.checkUsingIsDigitMethod(INPUT_WITH_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingIsDigitMethod(INPUT_WITHOUT_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingIsDigitMethod(""));
+        assertFalse(StrContainsNumberUtils.checkUsingIsDigitMethod(null));
+    }
+
+    @Test
+    public void givenInputString_whenUsingStreamApi_ThenCheck() {
+        assertTrue(StrContainsNumberUtils.checkUsingStreamApi(INPUT_WITH_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingStreamApi(INPUT_WITHOUT_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingStreamApi(""));
+        assertFalse(StrContainsNumberUtils.checkUsingStreamApi(null));
+    }
+
+    @Test
+    public void givenInputString_whenUsingApacheCommonsLang_ThenCheck() {
+        assertTrue(StrContainsNumberUtils.checkUsingApacheCommonsLang(INPUT_WITH_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingApacheCommonsLang(INPUT_WITHOUT_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingApacheCommonsLang(""));
+        assertFalse(StrContainsNumberUtils.checkUsingApacheCommonsLang(null));
+    }
+
+    @Test
+    public void givenInputString_whenUsingGuava_ThenCheck() {
+        assertTrue(StrContainsNumberUtils.checkUsingGuava(INPUT_WITH_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingGuava(INPUT_WITHOUT_NUMBERS));
+        assertFalse(StrContainsNumberUtils.checkUsingGuava(""));
+        assertFalse(StrContainsNumberUtils.checkUsingGuava(null));
+    }
+
+}

core-java-modules/core-java-string-operations-7/src/test/java/com/baeldung/unicode/UnicodeLetterCheckerUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.unicode;
+
+import org.junit.Test;
+import static org.junit.Assert.assertTrue;
+
+public class UnicodeLetterCheckerUnitTest {
+    @Test
+    public void givenString_whenUsingIsLetter_thenReturnTrue() {
+        UnicodeLetterChecker checker = new UnicodeLetterChecker();
+
+        boolean isUnicodeLetter = checker.characterClassCheck("HelloWorld");
+        assertTrue(isUnicodeLetter);
+    }
+
+    @Test
+    public void givenString_whenUsingRegex_thenReturnTrue() {
+        UnicodeLetterChecker checker = new UnicodeLetterChecker();
+
+        boolean isUnicodeLetter = checker.regexCheck("HelloWorld");
+        assertTrue(isUnicodeLetter);
+    }
+
+    @Test
+    public void givenString_whenUsingIsAlpha_thenReturnTrue() {
+        UnicodeLetterChecker checker = new UnicodeLetterChecker();
+
+        boolean isUnicodeLetter = checker.isAlphaCheck("HelloWorld");
+        assertTrue(isUnicodeLetter);
+    }
+
+    @Test
+    public void givenString_whenUsingStreams_thenReturnTrue() {
+        UnicodeLetterChecker checker = new UnicodeLetterChecker();
+
+        boolean isUnicodeLetter = checker.StreamsCheck("HelloWorld");
+        assertTrue(isUnicodeLetter);
+    }
+}

core-java-modules/core-java-strings/src/test/java/com/baeldung/passstringbyreference/Dummy.java

@@ -0,0 +1,14 @@
+package com.baeldung.passstringbyreference;
+
+public class Dummy {
+
+    String dummyString;
+
+    public String getDummyString() {
+        return dummyString;
+    }
+
+    public void setDummyString(String dummyString) {
+        this.dummyString = dummyString;
+    }
+}

core-java-modules/core-java-strings/src/test/java/com/baeldung/passstringbyreference/PassStringUnitTest.java

@@ -0,0 +1,85 @@
+package com.baeldung.passstringbyreference;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import org.junit.jupiter.api.Test;
+
+class PassStringUnitTest {
+
+    @Test
+    void givenAString_whenPassedToVoidMethod_thenStringIsNotModified() {
+        String s = "hello";
+        concatStringWithNoReturn(s);
+        assertEquals("hello", s);
+    }
+
+    void concatStringWithNoReturn(String input) {
+        input += " world";
+        assertEquals("hello world", input);
+    }
+
+    @Test
+    void givenAString_whenPassedToMethodAndReturnNewString_thenStringIsModified() {
+        String s = "hello";
+        assertEquals("hello world", concatStringWithReturn(s));
+    }
+
+    String concatStringWithReturn(String input) {
+        return input + " world";
+    }
+
+    @Test
+    void givenAString_whenPassStringBuilderToVoidMethod_thenConcatNewStringOk() {
+        StringBuilder builder = new StringBuilder("hello");
+        concatWithStringBuilder(builder);
+
+        assertEquals("hello world", builder.toString());
+    }
+
+    void concatWithStringBuilder(StringBuilder input) {
+        input.append(" world");
+    }
+
+    @Test
+    void givenAString_whenPassStringBufferToVoidMethod_thenConcatNewStringOk() {
+        StringBuffer builder = new StringBuffer("hello");
+        concatWithStringBuffer(builder);
+
+        assertEquals("hello world", builder.toString());
+    }
+
+    void concatWithStringBuffer(StringBuffer input) {
+        input.append(" world");
+    }
+
+    @Test
+    void givenObjectWithStringField_whenSetDifferentValue_thenObjectIsModified() {
+        Dummy dummy = new Dummy();
+        assertNull(dummy.getDummyString());
+        modifyStringValueInInputObject(dummy, "hello world");
+        assertEquals("hello world", dummy.getDummyString());
+    }
+
+    void modifyStringValueInInputObject(Dummy dummy, String dummyString) {
+        dummy.setDummyString(dummyString);
+    }
+
+    @Test
+    void givenObjectWithStringField_whenSetDifferentValueWithStringBuilder_thenSetStringInNewObject() {
+        assertEquals("hello world", getDummy("hello", "world").getDummyString());
+    }
+
+    Dummy getDummy(String hello, String world) {
+        StringBuilder builder = new StringBuilder();
+
+        builder.append(hello)
+          .append(" ")
+          .append(world);
+
+        Dummy dummy = new Dummy();
+        dummy.setDummyString(builder.toString());
+
+        return dummy;
+    }
+}

core-java-modules/pom.xml

@@ -73,6 +73,7 @@
         <module>core-java-arrays-multidimensional</module>
         <module>core-java-arrays-convert</module>
         <module>core-java-arrays-operations-basic</module>
+        <module>core-java-arrays-operations-basic-2</module>
         <module>core-java-arrays-operations-advanced</module>
         <module>core-java-arrays-operations-advanced-2</module>
         <module>core-java-booleans</module>

data-structures/src/main/java/com/baeldung/avltree/AVLTree.java

@@ -42,17 +42,17 @@ public class AVLTree {
         return root == null ? -1 : root.height;
     }
 
-    private Node insert(Node node, int key) {
-        if (node == null) {
+    private Node insert(Node root, int key) {
+        if (root == null) {
             return new Node(key);
-        } else if (node.key > key) {
-            node.left = insert(node.left, key);
-        } else if (node.key < key) {
-            node.right = insert(node.right, key);
+        } else if (root.key > key) {
+            root.left = insert(root.left, key);
+        } else if (root.key < key) {
+            root.right = insert(root.right, key);
         } else {
             throw new RuntimeException("duplicate Key!");
         }
-        return rebalance(node);
+        return rebalance(root);
     }
 
     private Node delete(Node node, int key) {

gradle-modules/gradle/gradle-fat-jar/build.gradle

@@ -8,8 +8,10 @@ buildscript {
     }
 }
 
-apply plugin: 'java'
-apply plugin: 'com.github.johnrengelman.shadow'
+plugins {
+  id 'com.github.johnrengelman.shadow' version '7.1.2'
+  id 'java'
+}
 
 repositories {
     mavenCentral()
@@ -30,7 +32,7 @@ task customFatJar(type: Jar) {
     manifest {
         attributes 'Main-Class': 'com.baeldung.fatjar.Application'
     }
-    baseName = 'all-in-one-jar'
+    archiveBaseName = 'all-in-one-jar'
     duplicatesStrategy = DuplicatesStrategy.EXCLUDE
     from { configurations.runtimeClasspath.collect { it.isDirectory() ? it : zipTree(it) } }
     with jar

jackson-simple/pom.xml

@@ -33,7 +33,7 @@
     </build>
 
     <properties>
-        <jackson.version>2.14.2</jackson.version>
+        <jackson.version>2.15.2</jackson.version>
         <java.version>17</java.version>
     </properties>
 

libraries-io/README.md

@@ -3,4 +3,4 @@
 
 - [Transferring a File Through SFTP in Java](https://www.baeldung.com/java-file-sftp)
 - [How to Create Password-Protected Zip Files and Unzip Them in Java](https://www.baeldung.com/java-password-protected-zip-unzip)
-
+- [How to Create CSV File from POJO with Custom Column Headers and Positions](https://www.baeldung.com/java-create-csv-pojo-customize-columns)

libraries-llms/pom.xml

@@ -0,0 +1,43 @@
+<?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>libraries-llms</artifactId>
+    <name>libraries-llms</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <!-- dependencies for langchain4j -->
+        <dependency>
+            <groupId>dev.langchain4j</groupId>
+            <artifactId>langchain4j</artifactId>
+            <version>${langchain4j.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>dev.langchain4j</groupId>
+            <artifactId>langchain4j-embeddings</artifactId>
+            <version>${langchain4j.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>dev.langchain4j</groupId>
+            <artifactId>langchain4j-open-ai</artifactId>
+            <version>${langchain4j.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>dev.langchain4j</groupId>
+            <artifactId>langchain4j-embeddings-all-minilm-l6-v2</artifactId>
+            <version>${langchain4j.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <langchain4j.version>0.23.0</langchain4j.version>
+    </properties>
+
+</project>

libraries-llms/src/test/java/com/baeldung/langchain/ChainWithDocumentLiveTest.java

@@ -0,0 +1,65 @@
+package com.baeldung.langchain;
+
+import static dev.langchain4j.data.document.FileSystemDocumentLoader.loadDocument;
+import static java.time.Duration.ofSeconds;
+import static org.junit.Assert.assertNotNull;
+
+import java.nio.file.Paths;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import dev.langchain4j.chain.ConversationalRetrievalChain;
+import dev.langchain4j.data.document.Document;
+import dev.langchain4j.data.document.splitter.DocumentSplitters;
+import dev.langchain4j.data.segment.TextSegment;
+import dev.langchain4j.memory.chat.MessageWindowChatMemory;
+import dev.langchain4j.model.chat.ChatLanguageModel;
+import dev.langchain4j.model.embedding.AllMiniLmL6V2EmbeddingModel;
+import dev.langchain4j.model.embedding.EmbeddingModel;
+import dev.langchain4j.model.input.PromptTemplate;
+import dev.langchain4j.model.openai.OpenAiChatModel;
+import dev.langchain4j.retriever.EmbeddingStoreRetriever;
+import dev.langchain4j.store.embedding.EmbeddingStore;
+import dev.langchain4j.store.embedding.EmbeddingStoreIngestor;
+import dev.langchain4j.store.embedding.inmemory.InMemoryEmbeddingStore;
+
+public class ChainWithDocumentLiveTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(ChainWithDocumentLiveTest.class);
+
+    @Test
+    public void givenChainWithDocument_whenPrompted_thenValidResponse() {
+        EmbeddingModel embeddingModel = new AllMiniLmL6V2EmbeddingModel();
+
+        EmbeddingStore<TextSegment> embeddingStore = new InMemoryEmbeddingStore<>();
+
+        EmbeddingStoreIngestor ingestor = EmbeddingStoreIngestor.builder()
+            .documentSplitter(DocumentSplitters.recursive(500, 0))
+            .embeddingModel(embeddingModel)
+            .embeddingStore(embeddingStore)
+            .build();
+
+        Document document = loadDocument(Paths.get("src/test/resources/example-files/simpson's_adventures.txt"));
+        ingestor.ingest(document);
+
+        ChatLanguageModel chatModel = OpenAiChatModel.builder()
+            .apiKey(Constants.OPENAI_API_KEY)
+            .timeout(ofSeconds(60))
+            .build();
+
+        ConversationalRetrievalChain chain = ConversationalRetrievalChain.builder()
+            .chatLanguageModel(chatModel)
+            .retriever(EmbeddingStoreRetriever.from(embeddingStore, embeddingModel))
+            .chatMemory(MessageWindowChatMemory.withMaxMessages(10))
+            .promptTemplate(PromptTemplate.from("Answer the following question to the best of your ability: {{question}}\n\nBase your answer on the following information:\n{{information}}"))
+            .build();
+
+        String answer = chain.execute("Who is Simpson?");
+
+        logger.info(answer);
+        assertNotNull(answer);
+    }
+
+}

libraries-llms/src/test/java/com/baeldung/langchain/ChatWithDocumentLiveTest.java

@@ -0,0 +1,81 @@
+package com.baeldung.langchain;
+
+import static dev.langchain4j.data.document.FileSystemDocumentLoader.loadDocument;
+import static dev.langchain4j.model.openai.OpenAiModelName.GPT_3_5_TURBO;
+import static java.time.Duration.ofSeconds;
+import static java.util.stream.Collectors.joining;
+import static org.junit.Assert.assertNotNull;
+
+import java.nio.file.Paths;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import dev.langchain4j.data.document.Document;
+import dev.langchain4j.data.document.DocumentSplitter;
+import dev.langchain4j.data.document.splitter.DocumentSplitters;
+import dev.langchain4j.data.embedding.Embedding;
+import dev.langchain4j.data.message.AiMessage;
+import dev.langchain4j.data.segment.TextSegment;
+import dev.langchain4j.model.chat.ChatLanguageModel;
+import dev.langchain4j.model.embedding.AllMiniLmL6V2EmbeddingModel;
+import dev.langchain4j.model.embedding.EmbeddingModel;
+import dev.langchain4j.model.input.Prompt;
+import dev.langchain4j.model.input.PromptTemplate;
+import dev.langchain4j.model.openai.OpenAiChatModel;
+import dev.langchain4j.model.openai.OpenAiTokenizer;
+import dev.langchain4j.store.embedding.EmbeddingMatch;
+import dev.langchain4j.store.embedding.EmbeddingStore;
+import dev.langchain4j.store.embedding.inmemory.InMemoryEmbeddingStore;
+
+public class ChatWithDocumentLiveTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(ChatWithDocumentLiveTest.class);
+
+    @Test
+    public void givenDocument_whenPrompted_thenValidResponse() {
+        Document document = loadDocument(Paths.get("src/test/resources/example-files/simpson's_adventures.txt"));
+        DocumentSplitter splitter = DocumentSplitters.recursive(100, 0, new OpenAiTokenizer(GPT_3_5_TURBO));
+        List<TextSegment> segments = splitter.split(document);
+
+        EmbeddingModel embeddingModel = new AllMiniLmL6V2EmbeddingModel();
+        List<Embedding> embeddings = embeddingModel.embedAll(segments)
+            .content();
+        EmbeddingStore<TextSegment> embeddingStore = new InMemoryEmbeddingStore<>();
+        embeddingStore.addAll(embeddings, segments);
+
+        String question = "Who is Simpson?";
+        Embedding questionEmbedding = embeddingModel.embed(question)
+            .content();
+        int maxResults = 3;
+        double minScore = 0.7;
+        List<EmbeddingMatch<TextSegment>> relevantEmbeddings = embeddingStore.findRelevant(questionEmbedding, maxResults, minScore);
+
+        PromptTemplate promptTemplate = PromptTemplate.from("Answer the following question to the best of your ability:\n" + "\n" + "Question:\n" + "{{question}}\n" + "\n" + "Base your answer on the following information:\n" + "{{information}}");
+
+        String information = relevantEmbeddings.stream()
+            .map(match -> match.embedded()
+                .text())
+            .collect(joining("\n\n"));
+
+        Map<String, Object> variables = new HashMap<>();
+        variables.put("question", question);
+        variables.put("information", information);
+
+        Prompt prompt = promptTemplate.apply(variables);
+        ChatLanguageModel chatModel = OpenAiChatModel.builder()
+            .apiKey(Constants.OPENAI_API_KEY)
+            .timeout(ofSeconds(60))
+            .build();
+        AiMessage aiMessage = chatModel.generate(prompt.toUserMessage())
+            .content();
+
+        logger.info(aiMessage.text());
+        assertNotNull(aiMessage.text());
+    }
+
+}

libraries-llms/src/test/java/com/baeldung/langchain/ChatWithMemoryLiveTest.java

@@ -0,0 +1,43 @@
+package com.baeldung.langchain;
+
+import static dev.langchain4j.data.message.UserMessage.userMessage;
+import static dev.langchain4j.model.openai.OpenAiModelName.GPT_3_5_TURBO;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertNotNull;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import dev.langchain4j.data.message.AiMessage;
+import dev.langchain4j.memory.ChatMemory;
+import dev.langchain4j.memory.chat.TokenWindowChatMemory;
+import dev.langchain4j.model.chat.ChatLanguageModel;
+import dev.langchain4j.model.openai.OpenAiChatModel;
+import dev.langchain4j.model.openai.OpenAiTokenizer;
+
+public class ChatWithMemoryLiveTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(ChatWithMemoryLiveTest.class);
+
+    @Test
+    public void givenMemory_whenPrompted_thenValidResponse() {
+        ChatLanguageModel model = OpenAiChatModel.withApiKey(Constants.OPENAI_API_KEY);
+        ChatMemory chatMemory = TokenWindowChatMemory.withMaxTokens(300, new OpenAiTokenizer(GPT_3_5_TURBO));
+
+        chatMemory.add(userMessage("Hello, my name is Kumar"));
+        AiMessage answer = model.generate(chatMemory.messages())
+            .content();
+        logger.info(answer.text());
+        chatMemory.add(answer);
+        assertNotNull(answer.text());
+
+        chatMemory.add(userMessage("What is my name?"));
+        AiMessage answerWithName = model.generate(chatMemory.messages())
+            .content();
+        logger.info(answerWithName.text());
+        chatMemory.add(answerWithName);
+        assertThat(answerWithName.text()).contains("Kumar");
+    }
+
+}

libraries-llms/src/test/java/com/baeldung/langchain/Constants.java

@@ -0,0 +1,12 @@
+package com.baeldung.langchain;
+
+public class Constants {
+    
+    /**
+     * A limited access key for access to OpenAI language models can be generated by first
+     * registering for free at (https://platform.openai.com/signup) and then by navigating
+     * to "Create new secret key" page at (https://platform.openai.com/account/api-keys).
+     */
+    public static String OPENAI_API_KEY = "<OPENAI_API_KEY>";
+
+}

libraries-llms/src/test/java/com/baeldung/langchain/PromptTemplatesLiveTest.java

@@ -0,0 +1,41 @@
+package com.baeldung.langchain;
+
+import static dev.langchain4j.model.openai.OpenAiModelName.GPT_3_5_TURBO;
+import static org.junit.Assert.assertNotNull;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import dev.langchain4j.model.chat.ChatLanguageModel;
+import dev.langchain4j.model.input.Prompt;
+import dev.langchain4j.model.input.PromptTemplate;
+import dev.langchain4j.model.openai.OpenAiChatModel;
+
+public class PromptTemplatesLiveTest {
+    
+    private static final Logger logger = LoggerFactory.getLogger(PromptTemplatesLiveTest.class);
+
+    @Test
+    public void givenPromptTemplate_whenSuppliedInput_thenValidResponse() {
+        PromptTemplate promptTemplate = PromptTemplate.from("Tell me a {{adjective}} joke about {{content}}..");
+        Map<String, Object> variables = new HashMap<>();
+        variables.put("adjective", "funny");
+        variables.put("content", "humans");
+        Prompt prompt = promptTemplate.apply(variables);
+
+        ChatLanguageModel model = OpenAiChatModel.builder()
+            .apiKey(Constants.OPENAI_API_KEY)
+            .modelName(GPT_3_5_TURBO)
+            .temperature(0.3)
+            .build();
+
+        String response = model.generate(prompt.text());
+        logger.info(response);
+        assertNotNull(response);
+    }
+
+}

libraries-llms/src/test/java/com/baeldung/langchain/ServiceWithToolsLiveTest.java

@@ -0,0 +1,49 @@
+package com.baeldung.langchain;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import dev.langchain4j.agent.tool.Tool;
+import dev.langchain4j.memory.chat.MessageWindowChatMemory;
+import dev.langchain4j.model.openai.OpenAiChatModel;
+import dev.langchain4j.service.AiServices;
+
+public class ServiceWithToolsLiveTest {
+    
+    private static final Logger logger = LoggerFactory.getLogger(ServiceWithToolsLiveTest.class);
+
+    static class Calculator {
+        @Tool("Calculates the length of a string")
+        int stringLength(String s) {
+            return s.length();
+        }
+
+        @Tool("Calculates the sum of two numbers")
+        int add(int a, int b) {
+            return a + b;
+        }
+    }
+
+    interface Assistant {
+        String chat(String userMessage);
+    }
+
+    @Test
+    public void givenServiceWithTools_whenPrompted_thenValidResponse() {
+        Assistant assistant = AiServices.builder(Assistant.class)
+            .chatLanguageModel(OpenAiChatModel.withApiKey(Constants.OPENAI_API_KEY))
+            .tools(new Calculator())
+            .chatMemory(MessageWindowChatMemory.withMaxMessages(10))
+            .build();
+
+        String question = "What is the sum of the numbers of letters in the words \"language\" and \"model\"?";
+        String answer = assistant.chat(question);
+
+        logger.info(answer);
+        assertThat(answer).contains("13");
+    }
+
+}

libraries-llms/src/test/resources/example-files/simpson's_adventures.txt

@@ -0,0 +1,28 @@
+Once upon a time in the town of VeggieVille, there lived a cheerful carrot named Simpson.
+Simpson was a radiant carrot, always beaming with joy and positivity.
+His vibrant orange skin and lush green top were a sight to behold, but it was his infectious laughter and warm personality that really set him apart.
+
+Simpson had a diverse group of friends, each a vegetable with their own unique characteristics.
+There was Bella the blushing beetroot, always ready with a riddle or two; Timmy the timid tomato, a gentle soul with a heart of gold; and Percy the prankster potato, whose jokes always brought a smile to everyone's faces.
+Despite their differences, they shared a close bond, their friendship as robust as their natural goodness.
+
+Their lives were filled with delightful adventures, from playing hide-and-seek amidst the leafy lettuce to swimming in the dewy droplets that pooled on the cabbage leaves.
+Their favorite place, though, was the sunlit corner of the vegetable patch, where they would bask in the warmth of the sun, share stories, and have hearty laughs.
+
+One day, a bunch of pesky caterpillars invaded VeggieVille.
+The vegetables were terrified, fearing they would be nibbled to nothingness.
+But Simpson, with his usual sunny disposition, had an idea.
+He proposed they host a grand feast for the caterpillars, with the juiciest leaves from the outskirts of the town.
+Simpson's optimism was contagious, and his friends eagerly joined in to prepare the feast.
+
+When the caterpillars arrived, they were pleasantly surprised.
+They enjoyed the feast and were so impressed with the vegetables' hospitality that they promised not to trouble VeggieVille again.
+In return, they agreed to help pollinate the flowers, contributing to a more lush and vibrant VeggieVille.
+
+Simpson's idea had saved the day, but he humbly attributed the success to their teamwork and friendship.
+They celebrated their victory with a grand party, filled with laughter, dance, and merry games.
+That night, under the twinkling stars, they made a pact to always stand by each other, come what may.
+
+From then on, the story of the happy carrot and his friends spread far and wide, a tale of friendship, unity, and positivity.
+Simpson, Bella, Timmy, and Percy continued to live their joyful lives, their laughter echoing through VeggieVille.
+And so, the tale of the happy carrot and his friends serves as a reminder that no matter the challenge, with optimism, teamwork, and a bit of creativity, anything is possible.

patterns-modules/axon/pom.xml

@@ -11,7 +11,7 @@
         <groupId>com.baeldung</groupId>
         <artifactId>parent-boot-2</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../parent-boot-2</relativePath>
+        <relativePath>../../parent-boot-2</relativePath>
     </parent>
 
     <dependencyManagement>