Merge branch 'master' into feature/ktln-43/working-with-lists-in-kotlin

algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/play2048/Board.java

@@ -0,0 +1,208 @@
+package com.baeldung.algorithms.play2048;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Board {
+    private static final Logger LOG = LoggerFactory.getLogger(Board.class);
+
+    private final int[][] board;
+
+    private final int score;
+
+    public Board(int size) {
+        assert(size > 0);
+
+        this.board = new int[size][];
+        this.score = 0;
+
+        for (int x = 0; x < size; ++x) {
+            this.board[x] = new int[size];
+            for (int y = 0; y < size; ++y) {
+                board[x][y] = 0;
+            }
+        }
+    }
+
+    private Board(int[][] board, int score) {
+        this.score = score;
+        this.board = new int[board.length][];
+
+        for (int x = 0; x < board.length; ++x) {
+            this.board[x] = Arrays.copyOf(board[x], board[x].length);
+        }
+    }
+
+    public int getSize() {
+        return board.length;
+    }
+
+    public int getScore() {
+        return score;
+    }
+
+    public int getCell(Cell cell) {
+        int x = cell.getX();
+        int y = cell.getY();
+        assert(x >= 0 && x < board.length);
+        assert(y >= 0 && y < board.length);
+
+        return board[x][y];
+    }
+
+    public boolean isEmpty(Cell cell) {
+        return getCell(cell) == 0;
+    }
+
+    public List<Cell> emptyCells() {
+        List<Cell> result = new ArrayList<>();
+        for (int x = 0; x < board.length; ++x) {
+            for (int y = 0; y < board[x].length; ++y) {
+                Cell cell = new Cell(x, y);
+                if (isEmpty(cell)) {
+                    result.add(cell);
+                }
+            }
+        }
+        return result;
+    }
+
+    public Board placeTile(Cell cell, int number) {
+        if (!isEmpty(cell)) {
+            throw new IllegalArgumentException("That cell is not empty");
+        }
+
+        Board result = new Board(this.board, this.score);
+        result.board[cell.getX()][cell.getY()] = number;
+        return result;
+    }
+
+    public Board move(Move move) {
+        // Clone the board
+        int[][] tiles = new int[this.board.length][];
+        for (int x = 0; x < this.board.length; ++x) {
+            tiles[x] = Arrays.copyOf(this.board[x], this.board[x].length);
+        }
+
+        LOG.debug("Before move: {}", Arrays.deepToString(tiles));
+        // If we're doing an Left/Right move then transpose the board to make it a Up/Down move
+        if (move == Move.LEFT || move == Move.RIGHT) {
+            tiles = transpose(tiles);
+            LOG.debug("After transpose: {}", Arrays.deepToString(tiles));
+        }
+        // If we're doing a Right/Down move then reverse the board.
+        // With the above we're now always doing an Up move
+        if (move == Move.DOWN || move == Move.RIGHT) {
+            tiles = reverse(tiles);
+            LOG.debug("After reverse: {}", Arrays.deepToString(tiles));
+        }
+        LOG.debug("Ready to move: {}", Arrays.deepToString(tiles));
+
+        // Shift everything up
+        int[][] result = new int[tiles.length][];
+        int newScore = 0;
+        for (int x = 0; x < tiles.length; ++x) {
+            LinkedList<Integer> thisRow = new LinkedList<>();
+            for (int y = 0; y < tiles[0].length; ++y) {
+                if (tiles[x][y] > 0) {
+                    thisRow.add(tiles[x][y]);
+                }
+            }
+
+            LOG.debug("Unmerged row: {}", thisRow);
+            LinkedList<Integer> newRow = new LinkedList<>();
+            while (thisRow.size() >= 2) {
+                int first = thisRow.pop();
+                int second = thisRow.peek();
+                LOG.debug("Looking at numbers {} and {}", first, second);
+                if (second == first) {
+                    LOG.debug("Numbers match, combining");
+                    int newNumber = first * 2;
+                    newRow.add(newNumber);
+                    newScore += newNumber;
+                    thisRow.pop();
+                } else {
+                    LOG.debug("Numbers don't match");
+                    newRow.add(first);
+                }
+            }
+            newRow.addAll(thisRow);
+            LOG.debug("Merged row: {}", newRow);
+
+            result[x] = new int[tiles[0].length];
+            for (int y = 0; y < tiles[0].length; ++y) {
+                if (newRow.isEmpty()) {
+                    result[x][y] = 0;
+                } else {
+                    result[x][y] = newRow.pop();
+                }
+            }
+        }
+        LOG.debug("After moves: {}", Arrays.deepToString(result));
+
+        // Un-reverse the board
+        if (move == Move.DOWN || move == Move.RIGHT) {
+            result = reverse(result);
+            LOG.debug("After reverse: {}", Arrays.deepToString(result));
+        }
+        // Un-transpose the board
+        if (move == Move.LEFT || move == Move.RIGHT) {
+            result = transpose(result);
+            LOG.debug("After transpose: {}", Arrays.deepToString(result));
+        }
+        return new Board(result, this.score + newScore);
+    }
+
+    private static int[][] transpose(int[][] input) {
+        int[][] result = new int[input.length][];
+
+        for (int x = 0; x < input.length; ++x) {
+            result[x] = new int[input[0].length];
+            for (int y = 0; y < input[0].length; ++y) {
+                result[x][y] = input[y][x];
+            }
+        }
+
+        return result;
+    }
+
+    private static int[][] reverse(int[][] input) {
+        int[][] result = new int[input.length][];
+
+        for (int x = 0; x < input.length; ++x) {
+            result[x] = new int[input[0].length];
+            for (int y = 0; y < input[0].length; ++y) {
+                result[x][y] = input[x][input.length - y - 1];
+            }
+        }
+
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return Arrays.deepToString(board);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        Board board1 = (Board) o;
+        return Arrays.deepEquals(board, board1.board);
+    }
+
+    @Override
+    public int hashCode() {
+        return Arrays.deepHashCode(board);
+    }
+}

algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/play2048/Cell.java

@@ -0,0 +1,26 @@
+package com.baeldung.algorithms.play2048;
+
+import java.util.StringJoiner;
+
+public class Cell {
+    private int x;
+    private int y;
+
+    public Cell(int x, int y) {
+        this.x = x;
+        this.y = y;
+    }
+
+    public int getX() {
+        return x;
+    }
+
+    public int getY() {
+        return y;
+    }
+
+    @Override
+    public String toString() {
+        return new StringJoiner(", ", Cell.class.getSimpleName() + "[", "]").add("x=" + x).add("y=" + y).toString();
+    }
+}

algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/play2048/Computer.java

@@ -0,0 +1,27 @@
+package com.baeldung.algorithms.play2048;
+
+import java.security.SecureRandom;
+import java.util.List;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Computer {
+    private static final Logger LOG = LoggerFactory.getLogger(Computer.class);
+
+    private final SecureRandom rng = new SecureRandom();
+
+    public Board makeMove(Board input) {
+        List<Cell> emptyCells = input.emptyCells();
+        LOG.info("Number of empty cells: {}", emptyCells.size());
+
+        double numberToPlace = rng.nextDouble();
+        LOG.info("New number probability: {}", numberToPlace);
+
+        int indexToPlace = rng.nextInt(emptyCells.size());
+        Cell cellToPlace = emptyCells.get(indexToPlace);
+        LOG.info("Placing number into empty cell: {}", cellToPlace);
+
+        return input.placeTile(cellToPlace, numberToPlace >= 0.9 ? 4 : 2);
+    }
+}

algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/play2048/Human.java

@@ -0,0 +1,126 @@
+package com.baeldung.algorithms.play2048;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.apache.commons.math3.util.Pair;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Human {
+    private static final Logger LOG = LoggerFactory.getLogger(Human.class);
+
+    public Board makeMove(Board input) {
+        // For each move in MOVE
+        //   Generate board from move
+        //   Generate Score for Board
+        // Return board with the best score
+        //
+        // Generate Score
+        //   If Depth Limit
+        //     Return Final Score
+        //   Total Score = 0
+        //   For every empty square in new board
+        //     Generate board with "2" in square
+        //       Calculate Score
+        //       Total Score += (Score * 0.9)
+        //     Generate board with "4" in square
+        //       Calculate Score
+        //       Total Score += (Score * 0.1)
+        //
+        // Calculate Score
+        //   For each move in MOVE
+        //     Generate board from move
+        //     Generate score for board
+        //   Return the best generated score
+
+        return Arrays.stream(Move.values())
+            .parallel()
+            .map(input::move)
+            .filter(board -> !board.equals(input))
+            .max(Comparator.comparingInt(board -> generateScore(board, 0)))
+            .orElse(input);
+    }
+
+    private int generateScore(Board board, int depth) {
+        if (depth >= 3) {
+            int finalScore = calculateFinalScore(board);
+            LOG.debug("Final score for board {}: {}", board,finalScore);
+            return finalScore;
+        }
+
+        return board.emptyCells().stream()
+            .parallel()
+            .flatMap(cell -> Stream.of(new Pair<>(cell, 2), new Pair<>(cell, 4)))
+            .mapToInt(move -> {
+                LOG.debug("Simulating move {} at depth {}", move, depth);
+                Board newBoard = board.placeTile(move.getFirst(), move.getSecond());
+                int boardScore = calculateScore(newBoard, depth + 1);
+                int calculatedScore = (int) (boardScore * (move.getSecond() == 2 ? 0.9 : 0.1));
+                LOG.debug("Calculated score for board {} and move {} at depth {}: {}", newBoard, move, depth, calculatedScore);
+                return calculatedScore;
+            })
+            .sum();
+    }
+
+    private int calculateScore(Board board, int depth) {
+        return Arrays.stream(Move.values())
+            .parallel()
+            .map(board::move)
+            .filter(moved -> !moved.equals(board))
+            .mapToInt(newBoard -> generateScore(newBoard, depth))
+            .max()
+            .orElse(0);
+    }
+
+    private int calculateFinalScore(Board board) {
+        List<List<Integer>> rowsToScore = new ArrayList<>();
+        for (int i = 0; i < board.getSize(); ++i) {
+            List<Integer> row = new ArrayList<>();
+            List<Integer> col = new ArrayList<>();
+
+            for (int j = 0; j < board.getSize(); ++j) {
+                row.add(board.getCell(new Cell(i, j)));
+                col.add(board.getCell(new Cell(j, i)));
+            }
+
+            rowsToScore.add(row);
+            rowsToScore.add(col);
+        }
+
+        return rowsToScore.stream()
+            .parallel()
+            .mapToInt(row -> {
+                List<Integer> preMerged = row.stream()
+                    .filter(value -> value != 0)
+                    .collect(Collectors.toList());
+
+                int numMerges = 0;
+                int monotonicityLeft = 0;
+                int monotonicityRight = 0;
+                for (int i = 0; i < preMerged.size() - 1; ++i) {
+                    Integer first = preMerged.get(i);
+                    Integer second = preMerged.get(i + 1);
+                    if (first.equals(second)) {
+                        ++numMerges;
+                    } else if (first > second) {
+                        monotonicityLeft += first - second;
+                    } else {
+                        monotonicityRight += second - first;
+                    }
+                }
+
+                int score = 1000;
+                score += 250 * row.stream().filter(value -> value == 0).count();
+                score += 750 * numMerges;
+                score -= 10 * row.stream().mapToInt(value -> value).sum();
+                score -= 50 * Math.min(monotonicityLeft, monotonicityRight);
+                return score;
+            })
+            .sum();
+    }
+}

algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/play2048/Move.java

@@ -0,0 +1,8 @@
+package com.baeldung.algorithms.play2048;
+
+public enum Move {
+    UP,
+    DOWN,
+    LEFT,
+    RIGHT
+}

algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/play2048/Play2048.java

@@ -0,0 +1,73 @@
+package com.baeldung.algorithms.play2048;
+
+public class Play2048 {
+    private static final int SIZE = 3;
+    private static final int INITIAL_NUMBERS = 2;
+
+    public static void main(String[] args) {
+        // The board and players
+        Board board = new Board(SIZE);
+        Computer computer = new Computer();
+        Human human = new Human();
+
+        // The computer has two moves first
+        System.out.println("Setup");
+        System.out.println("=====");
+        for (int i = 0; i < INITIAL_NUMBERS; ++i) {
+            board = computer.makeMove(board);
+        }
+
+        printBoard(board);
+        do {
+            board = human.makeMove(board);
+            System.out.println("Human move");
+            System.out.println("==========");
+            printBoard(board);
+
+            board = computer.makeMove(board);
+            System.out.println("Computer move");
+            System.out.println("=============");
+            printBoard(board);
+        } while (!board.emptyCells().isEmpty());
+
+        System.out.println("Final Score: " + board.getScore());
+
+    }
+
+    private static void printBoard(Board board) {
+        StringBuilder topLines = new StringBuilder();
+        StringBuilder midLines = new StringBuilder();
+        for (int x = 0; x < board.getSize(); ++x) {
+            topLines.append("+--------");
+            midLines.append("|        ");
+        }
+        topLines.append("+");
+        midLines.append("|");
+
+
+        for (int y = 0; y < board.getSize(); ++y) {
+            System.out.println(topLines);
+            System.out.println(midLines);
+            for (int x = 0; x < board.getSize(); ++x) {
+                Cell cell = new Cell(x, y);
+                System.out.print("|");
+                if (board.isEmpty(cell)) {
+                    System.out.print("        ");
+                } else {
+                    StringBuilder output = new StringBuilder(Integer.toString(board.getCell(cell)));
+                    while (output.length() < 8) {
+                        output.append(" ");
+                        if (output.length() < 8) {
+                            output.insert(0, " ");
+                        }
+                    }
+                    System.out.print(output);
+                }
+            }
+            System.out.println("|");
+            System.out.println(midLines);
+        }
+        System.out.println(topLines);
+        System.out.println("Score: " + board.getScore());
+    }
+}

algorithms-sorting-2/src/main/java/com/baeldung/algorithms/quicksort/DutchNationalFlagPartioning.java

@@ -5,21 +5,21 @@ import static com.baeldung.algorithms.quicksort.SortingUtils.swap;
 
 public class DutchNationalFlagPartioning {
 
-    public static Partition partition(int[] a, int begin, int end) {
+    public static Partition partition(int[] input, int begin, int end) {
         int lt = begin, current = begin, gt = end;
-        int partitioningValue = a[begin];
+        int partitioningValue = input[begin];
 
         while (current <= gt) {
-            int compareCurrent = compare(a[current], partitioningValue);
+            int compareCurrent = compare(input[current], partitioningValue);
             switch (compareCurrent) {
                 case -1:
-                    swap(a, current++, lt++);
+                    swap(input, current++, lt++);
                     break;
                 case 0:
                     current++;
                     break;
                 case 1:
-                    swap(a, current, gt--);
+                    swap(input, current, gt--);
                     break;
             }
         }

core-groovy-2/src/main/groovy/com/baeldung/determinedatatype/Person.groovy

@@ -0,0 +1,14 @@
+package com.baeldung.determinedatatype
+
+class Person {
+    
+    private int ageAsInt
+    private Double ageAsDouble
+    private String ageAsString
+    
+    Person() {}
+    Person(int ageAsInt) { this.ageAsInt =  ageAsInt}
+    Person(Double ageAsDouble) { this.ageAsDouble =  ageAsDouble}
+    Person(String ageAsString) { this.ageAsString =  ageAsString}    
+}
+class Student extends Person {}

core-groovy-2/src/test/groovy/com/baeldung/determinedatatype/PersonTest.groovy

@@ -0,0 +1,56 @@
+package com.baeldung.determinedatatype
+
+import org.junit.Assert
+import org.junit.Test
+import com.baeldung.determinedatatype.Person
+
+public class PersonTest {
+    
+    @Test
+    public void givenWhenParameterTypeIsInteger_thenReturnTrue() {
+        Person personObj = new Person(10)
+        Assert.assertTrue(personObj.ageAsInt instanceof Integer)
+    }
+    
+    @Test
+    public void givenWhenParameterTypeIsDouble_thenReturnTrue() {
+        Person personObj = new Person(10.0)
+        Assert.assertTrue((personObj.ageAsDouble).getClass() == Double)
+    }
+    
+    @Test
+    public void givenWhenParameterTypeIsString_thenReturnTrue() {
+        Person personObj = new Person("10 years")
+        Assert.assertTrue(personObj.ageAsString.class == String)
+    }
+    
+    @Test
+    public void givenClassName_WhenParameterIsInteger_thenReturnTrue() {
+        Assert.assertTrue(Person.class.getDeclaredField('ageAsInt').type == int.class)
+    }
+    
+    @Test
+    public void givenWhenObjectIsInstanceOfType_thenReturnTrue() {
+        Person personObj = new Person()
+        Assert.assertTrue(personObj instanceof Person)
+    }
+
+    @Test
+    public void givenWhenInstanceIsOfSubtype_thenReturnTrue() {
+        Student studentObj = new Student()
+        Assert.assertTrue(studentObj in Person)
+    }
+    
+    @Test
+    public void givenGroovyList_WhenFindClassName_thenReturnTrue() {
+      def ageList = ['ageAsString','ageAsDouble', 10]   
+      Assert.assertTrue(ageList.class == ArrayList)     
+      Assert.assertTrue(ageList.getClass() == ArrayList)
+    }
+    
+    @Test
+    public void givenGrooyMap_WhenFindClassName_thenReturnTrue() {
+      def ageMap = [ageAsString: '10 years', ageAsDouble: 10.0]
+      Assert.assertFalse(ageMap.class == LinkedHashMap)
+    }
+}

core-java-modules/core-java-14/README.md

@@ -9,3 +9,4 @@ This module contains articles about Java 14.
 - [Pattern Matching for instanceof in Java 14](https://www.baeldung.com/java-pattern-matching-instanceof)
 - [Helpful NullPointerExceptions in Java 14](https://www.baeldung.com/java-14-nullpointerexception)
 - [Foreign Memory Access API in Java 14](https://www.baeldung.com/java-foreign-memory-access)
+- [Java 14 Record Keyword](https://www.baeldung.com/java-record-keyword)

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

@@ -5,7 +5,7 @@ This module contains articles about the improvements to core Java features intro
 ### Relevant Articles:
 
 - [New Stream Collectors in Java 9](http://www.baeldung.com/java9-stream-collectors)
-- [Java 9 Convenience Factory Methods for Collections](https://www.baeldung.com/java-9-collections-factory-methods)
+- [Java Convenience Factory Methods for Collections](https://www.baeldung.com/java-9-collections-factory-methods)
 - [Java 9 Stream API Improvements](https://www.baeldung.com/java-9-stream-api)
 - [Java 9 java.util.Objects Additions](https://www.baeldung.com/java-9-objects-new)
 - [Java 9 CompletableFuture API Improvements](https://www.baeldung.com/java-9-completablefuture)

core-java-modules/core-java-arrays-guides/src/test/java/com/baeldung/arrays/JavaArraysToStringUnitTest.java

@@ -0,0 +1,42 @@
+package com.baeldung.arrays;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class JavaArraysToStringUnitTest {
+
+    @Test
+    public void givenInstanceOfArray_whenTryingToConvertToString_thenNameOfClassIsShown() {
+        Object[] arrayOfObjects = { "John", 2, true };
+        assertTrue(arrayOfObjects.toString().startsWith("[Ljava.lang.Object;"));
+    }
+
+    @Test
+    public void givenInstanceOfArray_whenUsingArraysToStringToConvert_thenValueOfObjectsAreShown() {
+        Object[] arrayOfObjects = { "John", 2, true };
+        assertEquals(Arrays.toString(arrayOfObjects), "[John, 2, true]");
+    }
+
+    @Test
+    public void givenInstanceOfDeepArray_whenUsingArraysDeepToStringToConvert_thenValueOfInnerObjectsAreShown() {
+        Object[] innerArray = { "We", "Are", "Inside" };
+        Object[] arrayOfObjects = { "John", 2, innerArray };
+        assertEquals(Arrays.deepToString(arrayOfObjects), "[John, 2, [We, Are, Inside]]");
+    }
+
+    @Test
+    public void givenInstanceOfDeepArray_whenUsingStreamsToConvert_thenValueOfObjectsAreShown() {
+        Object[] arrayOfObjects = { "John", 2, true };
+        List<String> listOfString = Stream.of(arrayOfObjects)
+          .map(Object::toString)
+          .collect(Collectors.toList());
+        assertEquals(listOfString.toString(), "[John, 2, true]");
+    }
+}

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

@@ -13,4 +13,5 @@ This module contains articles about advanced topics about multithreading with co
 - [Java Thread Deadlock and Livelock](https://www.baeldung.com/java-deadlock-livelock)
 - [Guide to AtomicStampedReference in Java](https://www.baeldung.com/java-atomicstampedreference)
 - [The ABA Problem in Concurrency](https://www.baeldung.com/cs/aba-concurrency)
+- [Introduction to Lock-Free Data Structures](https://www.baeldung.com/lock-free-programming)
 - [[<-- previous]](/core-java-modules/core-java-concurrency-advanced-2)

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

@@ -13,3 +13,4 @@ This module contains articles about concurrent Java collections
 - [Guide to the Java TransferQueue](http://www.baeldung.com/java-transfer-queue)
 - [Guide to the ConcurrentSkipListMap](http://www.baeldung.com/java-concurrent-skip-list-map)
 - [Guide to CopyOnWriteArrayList](http://www.baeldung.com/java-copy-on-write-arraylist)
+- [LinkedBlockingQueue vs ConcurrentLinkedQueue](https://www.baeldung.com/java-queue-linkedblocking-concurrentlinked)

core-java-modules/core-java-exceptions-2/src/test/java/com/baeldung/exceptions/TooManyOpenFilesExceptionLiveTest.java

@@ -0,0 +1,82 @@
+package com.baeldung.exceptions;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertFalse;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.AfterEach;
+
+
+public class TooManyOpenFilesExceptionLiveTest {
+
+    private File tempFile;
+
+    @BeforeEach
+    public void setUp() throws IOException {
+        tempFile = File.createTempFile("testForException", "tmp");
+    }
+
+    @AfterEach
+    public void tearDown() {
+        System.gc();
+        tempFile.delete();
+    }
+
+    @Test
+    public void whenNotClosingResoures_thenIOExceptionShouldBeThrown() {
+        try {
+            for (int x = 0; x < 1000000; x++) {
+                FileInputStream leakyHandle = new FileInputStream(tempFile);
+            }
+            Assertions.fail("Method Should Have Failed");
+        } catch (IOException e) {
+            assertTrue(e.getMessage().toLowerCase().contains("too many open files"));
+        } catch (Exception e) {
+            Assertions.fail("Unexpected exception");
+        }
+    }
+
+    @Test
+    public void whenClosingResoures_thenIOExceptionShouldNotBeThrown() {
+        try {
+            for (int x = 0; x < 1000000; x++) {
+                FileInputStream nonLeakyHandle = null;
+                try {
+                    nonLeakyHandle = new FileInputStream(tempFile);
+                } finally {
+                    if (nonLeakyHandle != null) {
+                        nonLeakyHandle.close();
+                    }
+                }
+            }
+        } catch (IOException e) {
+            assertFalse(e.getMessage().toLowerCase().contains("too many open files"));
+            Assertions.fail("Method Should Not Have Failed");
+        } catch (Exception e) {
+            Assertions.fail("Unexpected exception");
+        }
+    }
+
+    @Test
+    public void whenUsingTryWithResoures_thenIOExceptionShouldNotBeThrown() {
+        try {
+            for (int x = 0; x < 1000000; x++) {
+                try (FileInputStream nonLeakyHandle = new FileInputStream(tempFile)) {
+                    //Do something with the file
+                }
+            }
+        } catch (IOException e) {
+            assertFalse(e.getMessage().toLowerCase().contains("too many open files"));
+            Assertions.fail("Method Should Not Have Failed");
+        } catch (Exception e) {
+            Assertions.fail("Unexpected exception");
+        }
+    }
+}

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

@@ -51,14 +51,37 @@
             <scope>system</scope>
             <systemPath>${java.home}/../lib/tools.jar</systemPath>
         </dependency>
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm</artifactId>
+            <version>${asm.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm-util</artifactId>
+            <version>${asm.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.bcel</groupId>
+            <artifactId>bcel</artifactId>
+            <version>${bcel.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jol</groupId>
+            <artifactId>jol-core</artifactId>
+            <version>${jol-core.version}</version>
+        </dependency>
     </dependencies>
 
     <properties>
         <assertj.version>3.6.1</assertj.version>
         <!-- instrumentation -->
-        <javaassist.version>3.21.0-GA</javaassist.version>
+        <javaassist.version>3.27.0-GA</javaassist.version>
         <esapi.version>2.1.0.1</esapi.version>
         <sun.tools.version>1.8.0</sun.tools.version>
+        <jol-core.version>0.10</jol-core.version>
+        <asm.version>8.0.1</asm.version>
+        <bcel.version>6.5.0</bcel.version>
     </properties>
 
 </project>

core-java-modules/core-java-jvm/src/test/java/com/baeldung/boolsize/BooleanSizeUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.boolsize;
+
+import org.junit.Test;
+import org.openjdk.jol.info.ClassLayout;
+import org.openjdk.jol.vm.VM;
+
+public class BooleanSizeUnitTest {
+
+    @Test
+    public void printingTheVMDetails() {
+        System.out.println(VM.current().details());
+    }
+
+    @Test
+    public void printingTheBoolWrapper() {
+        System.out.println(ClassLayout.parseClass(BooleanWrapper.class).toPrintable());
+    }
+
+    @Test
+    public void printingTheBoolArray() {
+        boolean[] value = new boolean[3];
+
+        System.out.println(ClassLayout.parseInstance(value).toPrintable());
+    }
+}

core-java-modules/core-java-jvm/src/test/java/com/baeldung/boolsize/BooleanWrapper.java

@@ -0,0 +1,5 @@
+package com.baeldung.boolsize;
+
+class BooleanWrapper {
+    private boolean value;
+}

core-java-modules/core-java-jvm/src/test/java/com/baeldung/bytecode/ViewBytecodeUnitTest.java

@@ -0,0 +1,51 @@
+package com.baeldung.bytecode;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.io.StringWriter;
+
+import org.apache.bcel.Repository;
+import org.apache.bcel.classfile.JavaClass;
+import org.junit.Test;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.util.TraceClassVisitor;
+import javassist.ClassPool;
+import javassist.NotFoundException;
+import javassist.bytecode.ClassFile;
+
+public class ViewBytecodeUnitTest {
+    
+    @Test
+    public void whenUsingASM_thenReadBytecode() throws IOException {
+        ClassReader reader = new ClassReader("java.lang.Object");
+        StringWriter sw = new StringWriter();
+        TraceClassVisitor tcv = new TraceClassVisitor(new PrintWriter(sw));
+        reader.accept(tcv, 0); 
+        
+        assertTrue(sw.toString().contains("public class java/lang/Object")); 
+    }
+    
+    @Test
+    public void whenUsingBCEL_thenReadBytecode() throws ClassNotFoundException {
+        JavaClass objectClazz = Repository.lookupClass("java.lang.Object");
+        
+        assertEquals(objectClazz.getClassName(), "java.lang.Object");   
+        assertEquals(objectClazz.getMethods().length, 14);
+        assertTrue(objectClazz.toString().contains("public class java.lang.Object"));
+    }
+    
+    @Test
+    public void whenUsingJavassist_thenReadBytecode() throws NotFoundException {
+        ClassPool cp = ClassPool.getDefault();
+        ClassFile cf = cp.get("java.lang.Object").getClassFile();
+        
+        assertEquals(cf.getName(), "java.lang.Object");
+        assertEquals(cf.getMethods().size(), 14);
+    }
+    
+}
+
+

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

@@ -6,7 +6,6 @@
 - [Java 8 Math New Methods](https://www.baeldung.com/java-8-math)
 - [Java 8 Unsigned Arithmetic Support](https://www.baeldung.com/java-unsigned-arithmetic)
 - [How to Separate Double into Integer and Decimal Parts](https://www.baeldung.com/java-separate-double-into-integer-decimal-parts)
-- [The strictfp Keyword in Java](https://www.baeldung.com/java-strictfp)
 - [Basic Calculator in Java](https://www.baeldung.com/java-basic-calculator)
 - [Overflow and Underflow in Java](https://www.baeldung.com/java-overflow-underflow)
 - [Obtaining a Power Set of a Set in Java](https://www.baeldung.com/java-power-set-of-a-set)

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

@@ -7,3 +7,6 @@ This module contains articles about types in Java
 - [Guide to the this Java Keyword](https://www.baeldung.com/java-this)
 - [Nested Classes in Java](https://www.baeldung.com/java-nested-classes)
 - [Marker Interfaces in Java](https://www.baeldung.com/java-marker-interfaces)
+- [Iterating Over Enum Values in Java](https://www.baeldung.com/java-enum-iteration)
+- [Attaching Values to Java Enum](https://www.baeldung.com/java-enum-values)
+- [A Guide to Java Enums](https://www.baeldung.com/a-guide-to-java-enums)

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

@@ -12,3 +12,4 @@ This module contains articles about Java operators
 - [The XOR Operator in Java](https://www.baeldung.com/java-xor-operator)
 - [Java Bitwise Operators](https://www.baeldung.com/java-bitwise-operators)
 - [Bitwise & vs Logical && Operators](https://www.baeldung.com/java-bitwise-vs-logical-and)
+- [Finding an Object’s Class in Java](https://www.baeldung.com/java-finding-class)

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

@@ -4,7 +4,6 @@ This module contains articles about core features in the Java language
 
 ### Relevant Articles: 
 - [Generate equals() and hashCode() with Eclipse](https://www.baeldung.com/java-eclipse-equals-and-hashcode)
-- [Iterating Over Enum Values in Java](https://www.baeldung.com/java-enum-iteration)
 - [Comparator and Comparable in Java](https://www.baeldung.com/java-comparator-comparable)
 - [Recursion In Java](https://www.baeldung.com/java-recursion)
 - [A Guide to the finalize Method in Java](https://www.baeldung.com/java-finalize)
@@ -12,8 +11,6 @@ This module contains articles about core features in the Java language
 - [Using Java Assertions](https://www.baeldung.com/java-assert)
 - [Synthetic Constructs in Java](https://www.baeldung.com/java-synthetic)
 - [Retrieving a Class Name in Java](https://www.baeldung.com/java-class-name)
-- [Attaching Values to Java Enum](https://www.baeldung.com/java-enum-values)
 - [The Java continue and break Keywords](https://www.baeldung.com/java-continue-and-break)
-- [A Guide to Java Enums](https://www.baeldung.com/a-guide-to-java-enums)
 - [Infinite Loops in Java](https://www.baeldung.com/infinite-loops-java)
 - [[More --> ]](/core-java-modules/core-java-lang-2)

core-java-modules/core-java-string-conversions/src/test/java/com/baeldung/stringtoint/StringToIntOrIntegerUnitTest.java

@@ -17,6 +17,15 @@ public class StringToIntOrIntegerUnitTest {
         assertThat(result).isEqualTo(42);
     }
 
+    @Test
+    public void givenBinaryString_whenParsingInt_shouldConvertToInt() {
+        String givenString = "101010";
+
+        int result = Integer.parseInt(givenString, 2);
+
+        assertThat(result).isEqualTo(42);
+    }
+
     @Test
     public void givenString_whenCallingIntegerValueOf_shouldConvertToInt() {
         String givenString = "42";
@@ -26,6 +35,15 @@ public class StringToIntOrIntegerUnitTest {
         assertThat(result).isEqualTo(new Integer(42));
     }
 
+    @Test
+    public void givenBinaryString_whenCallingIntegerValueOf_shouldConvertToInt() {
+        String givenString = "101010";
+
+        Integer result = Integer.valueOf(givenString, 2);
+
+        assertThat(result).isEqualTo(new Integer(42));
+    }
+  
     @Test 
     public void givenString_whenCallingValueOf_shouldCacheSomeValues() {
         for (int i = -128; i <= 127; i++) {

core-kotlin-modules/core-kotlin-lang-2/README.md

@@ -12,4 +12,5 @@ This module contains articles about core features in the Kotlin language.
 - [Comprehensive Guide to Null Safety in Kotlin](https://www.baeldung.com/kotlin-null-safety)
 - [Kotlin Scope Functions](https://www.baeldung.com/kotlin-scope-functions)
 - [If-Else Expression in Kotlin](https://www.baeldung.com/kotlin/if-else-expression)
+- [Checking Whether a lateinit var Is Initialized in Kotlin](https://www.baeldung.com/kotlin/checking-lateinit)
 - [[<-- Prev]](/core-kotlin-modules/core-kotlin-lang)

drools/README.MD

@@ -5,5 +5,4 @@ This module contains articles about Drools
 ### Relevant Articles:
 
 - [Introduction to Drools](https://www.baeldung.com/drools)
-- [Drools Using Rules from Excel Files](https://www.baeldung.com/drools-excel)
 - [An Example of Backward Chaining in Drools](https://www.baeldung.com/drools-backward-chaining)

guava-collections-map/pom.xml

@@ -16,12 +16,39 @@
 
     <build>
         <finalName>guava-collections-map</finalName>
+
         <resources>
             <resource>
                 <directory>src/main/resources</directory>
                 <filtering>true</filtering>
             </resource>
         </resources>
+
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>2.22.2</version>
+            </plugin>
+        </plugins>
     </build>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.vintage</groupId>
+            <artifactId>junit-vintage-engine</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <junit-jupiter.version>5.6.2</junit-jupiter.version>
+    </properties>
 </project>

guava-collections-set/pom.xml

@@ -13,8 +13,32 @@
         <relativePath>../parent-java</relativePath>
     </parent>
 
+    <build>
+        <finalName>guava-collections-set</finalName>
+
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>2.22.2</version>
+            </plugin>
+        </plugins>
+    </build>
+
     <dependencies>
         <!-- test scoped -->
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.vintage</groupId>
+            <artifactId>junit-vintage-engine</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
@@ -23,13 +47,10 @@
         </dependency>
     </dependencies>
 
-    <build>
-        <finalName>guava-collections-set</finalName>
-    </build>
-
     <properties>
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
+        <junit-jupiter.version>5.6.2</junit-jupiter.version>
     </properties>
 
 </project>

guava-collections/pom.xml

@@ -15,6 +15,25 @@
         <relativePath>../parent-java</relativePath>
     </parent>
 
+    <build>
+        <finalName>guava-collections</finalName>
+
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>2.22.2</version>
+            </plugin>
+        </plugins>
+    </build>
+
     <dependencies>
         <!-- utils -->
         <dependency>
@@ -27,7 +46,20 @@
             <artifactId>commons-lang3</artifactId>
             <version>${commons-lang3.version}</version>
         </dependency>
+
         <!-- test scoped -->
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.vintage</groupId>
+            <artifactId>junit-vintage-engine</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
@@ -44,16 +76,6 @@
         </dependency>
     </dependencies>
 
-    <build>
-        <finalName>guava-collections</finalName>
-        <resources>
-            <resource>
-                <directory>src/main/resources</directory>
-                <filtering>true</filtering>
-            </resource>
-        </resources>
-    </build>
-
     <properties>
         <!-- util -->
         <commons-collections4.version>4.1</commons-collections4.version>
@@ -61,6 +83,7 @@
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
         <java-hamcrest.version>2.0.0.0</java-hamcrest.version>
+        <junit-jupiter.version>5.6.2</junit-jupiter.version>
     </properties>
 
 </project>

guava-io/pom.xml

@@ -4,6 +4,9 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>guava-io</artifactId>
     <version>0.1.0-SNAPSHOT</version>
+    <properties>
+        <junit-jupiter.version>5.6.2</junit-jupiter.version>
+    </properties>
     <name>guava-io</name>
 
     <parent>
@@ -15,12 +18,35 @@
 
     <build>
         <finalName>guava-io</finalName>
+
         <resources>
             <resource>
                 <directory>src/main/resources</directory>
                 <filtering>true</filtering>
             </resource>
         </resources>
+
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>2.22.2</version>
+            </plugin>
+        </plugins>
     </build>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.vintage</groupId>
+            <artifactId>junit-vintage-engine</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
 </project>

guava-io/src/test/java/com/baeldung/guava/GuavaIOUnitTest.java

@@ -11,8 +11,11 @@ import java.io.FileOutputStream;
 import java.io.FileReader;
 import java.io.IOException;
 import java.net.URL;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.List;
 
+import org.junit.After;
 import org.junit.Test;
 
 import com.google.common.base.Charsets;
@@ -31,6 +34,21 @@ import com.google.common.io.Resources;
 
 public class GuavaIOUnitTest {
 
+    @After
+    public void afterEach() throws Exception {
+        deleteProducedFiles();
+    }
+
+    private void deleteProducedFiles() throws IOException {
+        deleteIfExists("test.out");
+        deleteIfExists("test_copy.in");
+        deleteIfExists("test_le.txt");
+    }
+
+    private void deleteIfExists(String fileName) throws IOException {
+        java.nio.file.Files.deleteIfExists(Paths.get("src", "test", "resources", fileName));
+    }
+
     @Test
     public void whenWriteUsingFiles_thenWritten() throws IOException {
         final String expectedValue = "Hello world";
@@ -206,5 +224,4 @@ public class GuavaIOUnitTest {
 
         assertEquals(value, result);
     }
-
 }

guava-io/src/test/resources/test1.in

@@ -0,0 +1 @@
+Hello world

guava-io/src/test/resources/test1_1.in

@@ -0,0 +1 @@
+Test

guava-io/src/test/resources/test2.in

@@ -0,0 +1,4 @@
+John
+Jane
+Adam
+Tom

guava-modules/guava-18/pom.xml

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

guava-modules/guava-19/pom.xml

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

guava-modules/guava-21/pom.xml

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

guava-modules/pom.xml

@@ -4,13 +4,16 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>guava-modules</artifactId>
     <name>guava-modules</name>
+    <properties>
+        <junit-jupiter.version>5.6.2</junit-jupiter.version>
+    </properties>
     <packaging>pom</packaging>
 
     <parent>
         <groupId>com.baeldung</groupId>
-        <artifactId>parent-modules</artifactId>
-        <version>1.0.0-SNAPSHOT</version>
-        <relativePath>..</relativePath>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-java</relativePath>
     </parent>
 
     <modules>
@@ -19,4 +22,28 @@
         <module>guava-21</module>
     </modules>
 
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>2.22.2</version>
+            </plugin>
+        </plugins>
+    </build>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.vintage</groupId>
+            <artifactId>junit-vintage-engine</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
 </project>

guava/pom.xml

@@ -15,13 +15,45 @@
         <relativePath>../parent-java</relativePath>
     </parent>
 
+    <build>
+        <finalName>guava</finalName>
+
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>2.22.2</version>
+            </plugin>
+        </plugins>
+    </build>
+
     <dependencies>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
             <version>${commons-lang3.version}</version>
         </dependency>
+
         <!-- test scoped -->
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.vintage</groupId>
+            <artifactId>junit-vintage-engine</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
@@ -30,18 +62,9 @@
         </dependency>
     </dependencies>
 
-    <build>
-        <finalName>guava</finalName>
-        <resources>
-            <resource>
-                <directory>src/main/resources</directory>
-                <filtering>true</filtering>
-            </resource>
-        </resources>
-    </build>
-
     <properties>
         <!-- testing -->
+        <junit-jupiter.version>5.6.2</junit-jupiter.version>
         <assertj.version>3.6.1</assertj.version>
     </properties>
 

jackson-modules/pom.xml

@@ -23,6 +23,16 @@
         <module>jackson-exceptions</module>
     </modules>
 
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>2.22.2</version>
+            </plugin>
+        </plugins>
+    </build>
+
     <dependencies>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
@@ -35,6 +45,22 @@
             <artifactId>jackson-dataformat-xml</artifactId>
             <version>${jackson.version}</version>
         </dependency>
+
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.vintage</groupId>
+            <artifactId>junit-vintage-engine</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
+    <properties>
+        <junit-jupiter.version>5.6.2</junit-jupiter.version>
+    </properties>
 </project>

jackson-simple/pom.xml

@@ -13,6 +13,25 @@
         <relativePath>../parent-java</relativePath>
     </parent>
 
+    <build>
+        <finalName>jackson-simple</finalName>
+
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>2.22.2</version>
+            </plugin>
+        </plugins>
+    </build>
+
     <dependencies>
         <!--jackson for xml -->
         <dependency>
@@ -20,7 +39,20 @@
             <artifactId>jackson-dataformat-xml</artifactId>
             <version>${jackson.version}</version>
         </dependency>
+
         <!-- test scoped -->
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.vintage</groupId>
+            <artifactId>junit-vintage-engine</artifactId>
+            <version>${junit-jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
@@ -29,18 +61,9 @@
         </dependency>
     </dependencies>
 
-    <build>
-        <finalName>jackson-simple</finalName>
-        <resources>
-            <resource>
-                <directory>src/main/resources</directory>
-                <filtering>true</filtering>
-            </resource>
-        </resources>
-    </build>
-
     <properties>
         <!-- testing -->
+        <junit-jupiter.version>5.6.2</junit-jupiter.version>
         <assertj.version>3.11.0</assertj.version>
     </properties>
 

jhipster-5/bookstore-monolith/pom.xml

@@ -225,6 +225,12 @@
             <groupId>io.dropwizard.metrics</groupId>
             <artifactId>metrics-core</artifactId>
         </dependency>
+        <dependency>
+            <groupId>net.bytebuddy</groupId>
+            <artifactId>byte-buddy</artifactId>
+            <version>${byte-buddy.version}</version>
+            <scope>test</scope>
+        </dependency>
         <!-- jhipster-needle-maven-add-dependency -->
     </dependencies>
 

libraries-3/README.md

@@ -16,5 +16,4 @@ Remember, for advanced libraries like [Jackson](/jackson) and [JUnit](/testing-m
 - [Introduction to Takes](https://www.baeldung.com/java-takes)
 - [Using NullAway to Avoid NullPointerExceptions](https://www.baeldung.com/java-nullaway)
 - [Introduction to Alibaba Arthas](https://www.baeldung.com/java-alibaba-arthas-intro)
-- [Quick Guide to Spring Cloud Circuit Breaker](https://www.baeldung.com/spring-cloud-circuit-breaker)
 - More articles [[<-- prev]](/libraries-2) [[next -->]](/libraries-4)

libraries-concurrency/coroutines-with-quasar/pom.xml

@@ -1,84 +0,0 @@
-<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>coroutines-with-quasar</artifactId>
-    <name>coroutines-with-quasar</name>
-
-    <parent>
-        <groupId>com.baeldung</groupId>
-        <artifactId>libraries-concurrency</artifactId>
-        <version>1.0.0-SNAPSHOT</version>
-    </parent>
-
-    <dependencies>
-        <dependency>
-            <groupId>co.paralleluniverse</groupId>
-            <artifactId>quasar-core</artifactId>
-            <version>0.8.0</version>
-        </dependency>
-        <dependency>
-            <groupId>co.paralleluniverse</groupId>
-            <artifactId>quasar-actors</artifactId>
-            <version>0.8.0</version>
-        </dependency>
-        <dependency>
-            <groupId>co.paralleluniverse</groupId>
-            <artifactId>quasar-reactive-streams</artifactId>
-            <version>0.8.0</version>
-        </dependency>
-    </dependencies>
-
-    <build>
-        <plugins>
-            <plugin>
-                <artifactId>maven-dependency-plugin</artifactId>
-                <version>3.1.2</version>
-                <executions>
-                    <execution>
-                        <id>getClasspathFilenames</id>
-                        <goals>
-                            <goal>properties</goal>
-                        </goals>
-                    </execution>
-                </executions>
-            </plugin>
-            <plugin>
-                <groupId>org.codehaus.mojo</groupId>
-                <artifactId>exec-maven-plugin</artifactId>
-                <version>1.6.0</version>
-                <configuration>
-                    <mainClass>com.baeldung.quasar.App</mainClass>
-                    <workingDirectory>target/classes</workingDirectory>
-                    <executable>java</executable>
-                    <arguments>
-                        <!-- Turn off before production -->
-                        <argument>-Dco.paralleluniverse.fibers.verifyInstrumentation=true</argument>
-
-                        <!-- Quasar Agent -->
-                        <argument>-javaagent:${co.paralleluniverse:quasar-core:jar}</argument>
-
-                        <!-- Classpath -->
-                        <argument>-classpath</argument>
-                        <classpath />
-
-                        <!-- Main class -->
-                        <argument>com.baeldung.quasar.App</argument>
-                    </arguments>
-                </configuration>
-            </plugin>
-            <plugin>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.8.0</version>
-            </plugin>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <configuration>
-                    <source>12</source>
-                    <target>12</target>
-                </configuration>
-            </plugin>
-        </plugins>
-    </build>
-</project>

libraries-concurrency/pom.xml

@@ -5,7 +5,6 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>libraries-concurrency</artifactId>
     <name>libraries-concurrency</name>
-    <packaging>pom</packaging>
 
     <parent>
         <artifactId>parent-modules</artifactId>
@@ -13,8 +12,70 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
 
-    <modules>
-        <!-- <module>coroutines-with-quasar</module>  --><!-- we haven't upgraded to Java 12 -->
-    </modules>
+    <dependencies>
+        <dependency>
+            <groupId>co.paralleluniverse</groupId>
+            <artifactId>quasar-core</artifactId>
+            <version>0.8.0</version>
+        </dependency>
+        <dependency>
+            <groupId>co.paralleluniverse</groupId>
+            <artifactId>quasar-actors</artifactId>
+            <version>0.8.0</version>
+        </dependency>
+        <dependency>
+            <groupId>co.paralleluniverse</groupId>
+            <artifactId>quasar-reactive-streams</artifactId>
+            <version>0.8.0</version>
+        </dependency>
+    </dependencies>
 
+    <build>
+        <plugins>
+            <plugin>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <version>3.1.2</version>
+                <executions>
+                    <execution>
+                        <id>getClasspathFilenames</id>
+                        <goals>
+                            <goal>properties</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>1.6.0</version>
+                <configuration>
+                    <mainClass>com.baeldung.quasar.App</mainClass>
+                    <workingDirectory>target/classes</workingDirectory>
+                    <executable>java</executable>
+                    <arguments>
+                        <!-- Turn off before production -->
+                        <argument>-Dco.paralleluniverse.fibers.verifyInstrumentation=true</argument>
+
+                        <!-- Quasar Agent -->
+                        <argument>-javaagent:${co.paralleluniverse:quasar-core:jar}</argument>
+
+                        <!-- Classpath -->
+                        <argument>-classpath</argument>
+                        <classpath />
+
+                        <!-- Main class -->
+                        <argument>com.baeldung.quasar.App</argument>
+                    </arguments>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>11</source>
+                    <target>11</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
 </project>

libraries-data-2/README.md

@@ -12,6 +12,7 @@ This module contains articles about libraries for data processing in Java.
 - [An Introduction to SuanShu](https://www.baeldung.com/suanshu)
 - [Intro to Derive4J](https://www.baeldung.com/derive4j)
 - [Java-R Integration](https://www.baeldung.com/java-r-integration)
+- [Univocity Parsers](https://www.baeldung.com/java-univocity-parsers)
 - More articles: [[<-- prev]](/../libraries-data)
 
 ##### Building the project

libraries-data-2/pom.xml

@@ -153,7 +153,13 @@
             <artifactId>renjin-script-engine</artifactId>
             <version>${renjin.version}</version>
         </dependency>
-         <dependency>
+        <dependency>
+            <groupId>net.bytebuddy</groupId>
+            <artifactId>byte-buddy</artifactId>
+            <version>${byte-buddy.version}</version>
+        <scope>test</scope>
+        </dependency>
+        <dependency>
             <groupId>org.apache.kafka</groupId>
             <artifactId>kafka-clients</artifactId>
             <version>${kafka.version}</version>

libraries-testing/pom.xml

@@ -151,6 +151,13 @@
             <scope>test</scope>
         </dependency>
 
+        <dependency>
+            <groupId>net.bytebuddy</groupId>
+            <artifactId>byte-buddy</artifactId>
+            <version>${byte-buddy.version}</version>
+            <scope>test</scope>
+        </dependency>
+
     </dependencies>
 
     <build>

logging-modules/log4j2/README.md

@@ -6,3 +6,4 @@
 - [Creating a Custom Log4j2 Appender](https://www.baeldung.com/log4j2-custom-appender)
 - [Get Log Output in JSON](http://www.baeldung.com/java-log-json-output)
 - [System.out.println vs Loggers](https://www.baeldung.com/java-system-out-println-vs-loggers)
+- [Log4j 2 Plugins](https://www.baeldung.com/log4j2-plugins)

netflix-modules/genie/README.md

@@ -1,3 +0,0 @@
-### Relevant Articles:
-
-- [Introduction to Netflix Genie](https://www.baeldung.com/netflix-genie-intro)

netty/src/main/java/com/baeldung/http/server/CustomHttpServerHandler.java

@@ -5,8 +5,6 @@ import static io.netty.handler.codec.http.HttpResponseStatus.CONTINUE;
 import static io.netty.handler.codec.http.HttpResponseStatus.OK;
 import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
 
-import java.util.Set;
-
 import io.netty.buffer.Unpooled;
 import io.netty.channel.ChannelFutureListener;
 import io.netty.channel.ChannelHandlerContext;
@@ -20,9 +18,6 @@ import io.netty.handler.codec.http.HttpObject;
 import io.netty.handler.codec.http.HttpRequest;
 import io.netty.handler.codec.http.HttpUtil;
 import io.netty.handler.codec.http.LastHttpContent;
-import io.netty.handler.codec.http.cookie.Cookie;
-import io.netty.handler.codec.http.cookie.ServerCookieDecoder;
-import io.netty.handler.codec.http.cookie.ServerCookieEncoder;
 import io.netty.util.CharsetUtil;
 
 public class CustomHttpServerHandler extends SimpleChannelInboundHandler<Object> {
@@ -45,22 +40,20 @@ public class CustomHttpServerHandler extends SimpleChannelInboundHandler<Object>
             }
 
             responseData.setLength(0);
-            responseData.append(ResponseBuilder.addRequestAttributes(request));
-            responseData.append(ResponseBuilder.addHeaders(request));
-            responseData.append(ResponseBuilder.addParams(request));
+            responseData.append(RequestUtils.formatParams(request));
         }
 
-        responseData.append(ResponseBuilder.addDecoderResult(request));
+        responseData.append(RequestUtils.evaluateDecoderResult(request));
 
         if (msg instanceof HttpContent) {
             HttpContent httpContent = (HttpContent) msg;
 
-            responseData.append(ResponseBuilder.addBody(httpContent));
-            responseData.append(ResponseBuilder.addDecoderResult(request));
+            responseData.append(RequestUtils.formatBody(httpContent));
+            responseData.append(RequestUtils.evaluateDecoderResult(request));
 
             if (msg instanceof LastHttpContent) {
                 LastHttpContent trailer = (LastHttpContent) msg;
-                responseData.append(ResponseBuilder.addLastResponse(request, trailer));
+                responseData.append(RequestUtils.prepareLastResponse(request, trailer));
                 writeResponse(ctx, trailer, responseData);
             }
         }
@@ -88,18 +81,6 @@ public class CustomHttpServerHandler extends SimpleChannelInboundHandler<Object>
                 .set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
         }
 
-        String cookieString = request.headers()
-            .get(HttpHeaderNames.COOKIE);
-        if (cookieString != null) {
-            Set<Cookie> cookies = ServerCookieDecoder.STRICT.decode(cookieString);
-            if (!cookies.isEmpty()) {
-                for (Cookie cookie : cookies) {
-                    httpResponse.headers()
-                        .add(HttpHeaderNames.SET_COOKIE, ServerCookieEncoder.STRICT.encode(cookie));
-                }
-            }
-        }
-
         ctx.write(httpResponse);
 
         if (!keepAlive) {

netty/src/main/java/com/baeldung/http/server/RequestUtils.java

@@ -7,32 +7,15 @@ import java.util.Map.Entry;
 import io.netty.buffer.ByteBuf;
 import io.netty.handler.codec.DecoderResult;
 import io.netty.handler.codec.http.HttpContent;
-import io.netty.handler.codec.http.HttpHeaderNames;
-import io.netty.handler.codec.http.HttpHeaders;
 import io.netty.handler.codec.http.HttpObject;
 import io.netty.handler.codec.http.HttpRequest;
 import io.netty.handler.codec.http.LastHttpContent;
 import io.netty.handler.codec.http.QueryStringDecoder;
 import io.netty.util.CharsetUtil;
 
-class ResponseBuilder {
+class RequestUtils {
 
-    static StringBuilder addRequestAttributes(HttpRequest request) {
-        StringBuilder responseData = new StringBuilder();
-        responseData.append("Version: ")
-            .append(request.protocolVersion())
-            .append("\r\n");
-        responseData.append("Host: ")
-            .append(request.headers()
-                .get(HttpHeaderNames.HOST, "unknown"))
-            .append("\r\n");
-        responseData.append("URI: ")
-            .append(request.uri())
-            .append("\r\n\r\n");
-        return responseData;
-    }
-
-    static StringBuilder addParams(HttpRequest request) {
+    static StringBuilder formatParams(HttpRequest request) {
         StringBuilder responseData = new StringBuilder();
         QueryStringDecoder queryStringDecoder = new QueryStringDecoder(request.uri());
         Map<String, List<String>> params = queryStringDecoder.parameters();
@@ -42,9 +25,9 @@ class ResponseBuilder {
                 List<String> vals = p.getValue();
                 for (String val : vals) {
                     responseData.append("Parameter: ")
-                        .append(key)
+                        .append(key.toUpperCase())
                         .append(" = ")
-                        .append(val)
+                        .append(val.toUpperCase())
                         .append("\r\n");
                 }
             }
@@ -53,24 +36,7 @@ class ResponseBuilder {
         return responseData;
     }
 
-    static StringBuilder addHeaders(HttpRequest request) {
-        StringBuilder responseData = new StringBuilder();
-        HttpHeaders headers = request.headers();
-        if (!headers.isEmpty()) {
-            for (Map.Entry<String, String> header : headers) {
-                CharSequence key = header.getKey();
-                CharSequence value = header.getValue();
-                responseData.append(key)
-                    .append(" = ")
-                    .append(value)
-                    .append("\r\n");
-            }
-            responseData.append("\r\n");
-        }
-        return responseData;
-    }
-
-    static StringBuilder addBody(HttpContent httpContent) {
+    static StringBuilder formatBody(HttpContent httpContent) {
         StringBuilder responseData = new StringBuilder();
         ByteBuf content = httpContent.content();
         if (content.isReadable()) {
@@ -81,7 +47,7 @@ class ResponseBuilder {
         return responseData;
     }
 
-    static StringBuilder addDecoderResult(HttpObject o) {
+    static StringBuilder evaluateDecoderResult(HttpObject o) {
         StringBuilder responseData = new StringBuilder();
         DecoderResult result = o.decoderResult();
 
@@ -94,7 +60,7 @@ class ResponseBuilder {
         return responseData;
     }
 
-    static StringBuilder addLastResponse(HttpRequest request, LastHttpContent trailer) {
+    static StringBuilder prepareLastResponse(HttpRequest request, LastHttpContent trailer) {
         StringBuilder responseData = new StringBuilder();
         responseData.append("Good Bye!\r\n");
 

netty/src/test/java/com/baeldung/http/server/HttpServerLiveTest.java

@@ -89,7 +89,7 @@ public class HttpServerLiveTest {
     }
 
     @Test
-    public void whenGetSent_thenCookieReceivedInResponse() throws Exception {
+    public void whenGetSent_thenResponseOK() throws Exception {
         DefaultFullHttpRequest request = createRequest(null);
 
         channel.writeAndFlush(request);
@@ -98,9 +98,6 @@ public class HttpServerLiveTest {
         assertEquals(200, response.getStatus());
         assertEquals("HTTP/1.1", response.getVersion());
 
-        Map<String, String> headers = response.getHeaders();
-        String cookies = headers.get("set-cookie");
-        assertTrue(cookies.contains("my-cookie"));
     }
 
     @After

parent-boot-2/pom.xml

@@ -32,11 +32,6 @@
             <groupId>io.rest-assured</groupId>
             <artifactId>rest-assured</artifactId>
         </dependency>
-        <dependency>
-            <groupId>net.bytebuddy</groupId>
-            <artifactId>byte-buddy</artifactId>
-            <version>${byte-buddy.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-test</artifactId>

patterns/solid/README.md

@@ -2,4 +2,4 @@
 
 - [A Solid Guide to Solid Principles](https://www.baeldung.com/solid-principles)
 - [Single Responsibility Principle in Java](https://www.baeldung.com/java-single-responsibility-principle)
-
+- [Open/Closed Principle in Java](https://www.baeldung.com/java-open-closed-principle)

pdf/README.md

@@ -5,3 +5,4 @@ This module contains articles about PDF files.
 ### Relevant Articles:
 - [PDF Conversions in Java](https://www.baeldung.com/pdf-conversions-java)
 - [Creating PDF Files in Java](https://www.baeldung.com/java-pdf-creation)
+- [Generating PDF Files Using Thymeleaf](https://www.baeldung.com/thymeleaf-generate-pdf)

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

@@ -60,6 +60,7 @@
     </dependencies>
 
     <properties>
+        <h2.version>1.4.200</h2.version>
         <postgresql.version>42.2.5.jre7</postgresql.version>
         <assertj-core.version>3.10.0</assertj-core.version>
         <commons-dbcp2.version>2.4.0</commons-dbcp2.version>

persistence-modules/core-java-persistence/src/test/java/com/baeldung/genkeys/JdbcInsertIdIntegrationTest.java

@@ -0,0 +1,93 @@
+package com.baeldung.genkeys;
+
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class JdbcInsertIdIntegrationTest {
+
+    private static final String QUERY = "insert into persons (name) values (?)";
+
+    private static Connection connection;
+
+    @BeforeClass
+    public static void setUp() throws Exception {
+        connection = DriverManager.getConnection("jdbc:h2:mem:generated-keys", "sa", "");
+        connection
+          .createStatement()
+          .execute("create table persons(id bigint auto_increment, name varchar(255))");
+    }
+
+    @AfterClass
+    public static void tearDown() throws SQLException {
+        connection
+          .createStatement()
+          .execute("drop table persons");
+        connection.close();
+    }
+
+    @Test
+    public void givenInsert_whenUsingAutoGenFlag_thenBeAbleToFetchTheIdAfterward() throws SQLException {
+        try (PreparedStatement statement = connection.prepareStatement(QUERY, Statement.RETURN_GENERATED_KEYS)) {
+            statement.setString(1, "Foo");
+            int affectedRows = statement.executeUpdate();
+            assertThat(affectedRows).isPositive();
+
+            try (ResultSet keys = statement.getGeneratedKeys()) {
+                assertThat(keys.next()).isTrue();
+                assertThat(keys.getLong(1)).isGreaterThanOrEqualTo(1);
+            }
+        }
+    }
+
+    @Test
+    public void givenInsert_whenUsingAutoGenFlagViaExecute_thenBeAbleToFetchTheIdAfterward() throws SQLException {
+        try (Statement statement = connection.createStatement()) {
+            String query = "insert into persons (name) values ('Foo')";
+            int affectedRows = statement.executeUpdate(query, Statement.RETURN_GENERATED_KEYS);
+            assertThat(affectedRows).isPositive();
+
+            try (ResultSet keys = statement.getGeneratedKeys()) {
+                assertThat(keys.next()).isTrue();
+                assertThat(keys.getLong(1)).isGreaterThanOrEqualTo(1);
+            }
+        }
+    }
+
+    @Test
+    public void givenInsert_whenUsingReturningCols_thenBeAbleToFetchTheIdAfterward() throws SQLException {
+        try (PreparedStatement statement = connection.prepareStatement(QUERY, new String[] { "id" })) {
+            statement.setString(1, "Foo");
+            int affectedRows = statement.executeUpdate();
+            assertThat(affectedRows).isPositive();
+
+            try (ResultSet keys = statement.getGeneratedKeys()) {
+                assertThat(keys.next()).isTrue();
+                assertThat(keys.getLong(1)).isGreaterThanOrEqualTo(1);
+            }
+        }
+    }
+
+    @Test
+    public void givenInsert_whenUsingReturningColsViaExecute_thenBeAbleToFetchTheIdAfterward() throws SQLException {
+        try (Statement statement = connection.createStatement()) {
+            String query = "insert into persons (name) values ('Foo')";
+            int affectedRows = statement.executeUpdate(query, new String[] { "id" });
+            assertThat(affectedRows).isPositive();
+
+            try (ResultSet keys = statement.getGeneratedKeys()) {
+                assertThat(keys.next()).isTrue();
+                assertThat(keys.getLong(1)).isGreaterThanOrEqualTo(1);
+            }
+        }
+    }
+}

persistence-modules/hibernate-enterprise/pom.xml

@@ -55,6 +55,12 @@
             <artifactId>hibernate-testing</artifactId>
             <version>${hibernate.version}</version>
         </dependency>
+        <dependency>
+            <groupId>net.bytebuddy</groupId>
+            <artifactId>byte-buddy</artifactId>
+            <version>${byte-buddy.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <repositories>

persistence-modules/java-jpa-2/README.md

@@ -13,4 +13,5 @@ This module contains articles about the Java Persistence API (JPA) in Java.
 - [JPA Annotation for the PostgreSQL TEXT Type](https://www.baeldung.com/jpa-annotation-postgresql-text-type)
 - [Mapping a Single Entity to Multiple Tables in JPA](https://www.baeldung.com/jpa-mapping-single-entity-to-multiple-tables)
 - [Constructing a JPA Query Between Unrelated Entities](https://www.baeldung.com/jpa-query-unrelated-entities)
+- [When Does JPA Set the Primary Key](https://www.baeldung.com/jpa-strategies-when-set-primary-key)
 - More articles: [[<-- prev]](/java-jpa)

persistence-modules/java-jpa-2/src/main/java/com/baeldung/jpa/generateidvalue/Admin.java

@@ -0,0 +1,36 @@
+package com.baeldung.jpa.generateidvalue;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.Id;
+import javax.persistence.Table;
+
+@Entity
+@Table(name = "app_admin")
+public class Admin {
+
+    @Id
+    @GeneratedValue
+    private Long id;
+
+    @Column(name = "admin_name")
+    private String name;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+}

persistence-modules/java-jpa-2/src/main/java/com/baeldung/jpa/generateidvalue/Article.java

@@ -0,0 +1,39 @@
+package com.baeldung.jpa.generateidvalue;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.SequenceGenerator;
+import javax.persistence.Table;
+
+@Entity
+@Table(name = "article")
+public class Article {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "article_gen")
+    @SequenceGenerator(name = "article_gen", sequenceName = "article_seq")
+    private Long id;
+
+    @Column(name = "article_name")
+    private String name;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+}

persistence-modules/java-jpa-2/src/main/java/com/baeldung/jpa/generateidvalue/IdGenerator.java

@@ -0,0 +1,48 @@
+package com.baeldung.jpa.generateidvalue;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.Table;
+
+@Table(name = "id_gen")
+@Entity
+public class IdGenerator {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(name = "gen_name")
+    private String gen_name;
+
+    @Column(name = "gen_value")
+    private Long gen_value;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getGen_name() {
+        return gen_name;
+    }
+
+    public void setGen_name(String gen_name) {
+        this.gen_name = gen_name;
+    }
+
+    public Long getGen_value() {
+        return gen_value;
+    }
+
+    public void setGen_value(Long gen_value) {
+        this.gen_value = gen_value;
+    }
+
+}

persistence-modules/java-jpa-2/src/main/java/com/baeldung/jpa/generateidvalue/Task.java

@@ -0,0 +1,39 @@
+package com.baeldung.jpa.generateidvalue;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.Table;
+import javax.persistence.TableGenerator;
+
+@Entity
+@Table(name = "task")
+public class Task {
+
+    @Id
+    @TableGenerator(name = "id_generator", table = "id_gen", pkColumnName = "gen_name", valueColumnName = "gen_value", pkColumnValue = "task_gen", initialValue = 10000, allocationSize = 10)
+    @GeneratedValue(strategy = GenerationType.TABLE, generator = "id_generator")
+    private Long id;
+
+    @Column(name = "name")
+    private String name;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+}

persistence-modules/java-jpa-2/src/main/java/com/baeldung/jpa/generateidvalue/User.java

@@ -0,0 +1,37 @@
+package com.baeldung.jpa.generateidvalue;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.Table;
+
+@Entity
+@Table(name = "app_user")
+public class User {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(name = "user_name")
+    private String name;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+}

persistence-modules/java-jpa-2/src/main/resources/META-INF/persistence.xml

@@ -184,4 +184,29 @@
                       value="false" />
         </properties>
     </persistence-unit>
+
+    <persistence-unit name="jpa-h2-primarykey">
+        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
+        <class>com.baeldung.jpa.generateidvalue.Admin</class>
+        <class>com.baeldung.jpa.generateidvalue.Article</class>
+        <class>com.baeldung.jpa.generateidvalue.IdGenerator</class>
+        <class>com.baeldung.jpa.generateidvalue.Task</class>
+        <class>com.baeldung.jpa.generateidvalue.User</class>
+        <exclude-unlisted-classes>true</exclude-unlisted-classes>
+        <properties>
+            <property name="javax.persistence.jdbc.driver"
+                      value="org.h2.Driver" />
+            <property name="javax.persistence.jdbc.url"
+                      value="jdbc:h2:mem:test" />
+            <property name="javax.persistence.jdbc.user" value="sa" />
+            <property name="javax.persistence.jdbc.password" value="" />
+            <property name="javax.persistence.sql-load-script-source"
+                      value="primary_key_generator.sql" />
+            <property name="eclipselink.ddl-generation" value="create-or-extend-tables" />
+            <property name="eclipselink.ddl-generation.output-mode" value="database" />
+            <property name="eclipselink.weaving" value="static" />
+            <property name="eclipselink.logging.level" value="FINE" />
+            <property name="eclipselink.jdbc.allow-native-sql-queries" value="true" />
+        </properties>
+    </persistence-unit>
 </persistence>

persistence-modules/java-jpa-2/src/main/resources/primary_key_generator.sql

@@ -0,0 +1,4 @@
+CREATE SEQUENCE article_seq MINVALUE 1 START WITH 50 INCREMENT BY 50;
+
+INSERT INTO id_gen (gen_name, gen_val) VALUES ('id_generator', 0); 
+INSERT INTO id_gen (gen_name, gen_val) VALUES ('task_gen', 10000);

persistence-modules/java-jpa-2/src/test/java/com/baeldung/jpa/generateidvalue/PrimaryKeyUnitTest.java

@@ -0,0 +1,81 @@
+package com.baeldung.jpa.generateidvalue;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.Persistence;
+
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+/**
+ * PrimaryKeyGeneratorTest class
+ * 
+ * @author shiwangzhihe@gmail.com
+ */
+public class PrimaryKeyUnitTest {
+    private static EntityManager entityManager;
+
+    @BeforeClass
+    public static void setup() {
+        EntityManagerFactory factory = Persistence.createEntityManagerFactory("jpa-h2-primarykey");
+        entityManager = factory.createEntityManager();
+    }
+
+    @Test
+    public void givenIdentityStrategy_whenCommitTransction_thenReturnPrimaryKey() {
+        User user = new User();
+        user.setName("TestName");
+
+        entityManager.getTransaction()
+            .begin();
+        entityManager.persist(user);
+        Assert.assertNull(user.getId());
+        entityManager.getTransaction()
+            .commit();
+
+        Long expectPrimaryKey = 1L;
+        Assert.assertEquals(expectPrimaryKey, user.getId());
+    }
+
+    @Test
+    public void givenTableStrategy_whenPersist_thenReturnPrimaryKey() {
+        Task task = new Task();
+        task.setName("Test Task");
+
+        entityManager.getTransaction()
+            .begin();
+        entityManager.persist(task);
+        Long expectPrimaryKey = 10000L;
+        Assert.assertEquals(expectPrimaryKey, task.getId());
+
+        entityManager.getTransaction()
+            .commit();
+    }
+
+    @Test
+    public void givenSequenceStrategy_whenPersist_thenReturnPrimaryKey() {
+        Article article = new Article();
+        article.setName("Test Name");
+
+        entityManager.getTransaction()
+            .begin();
+        entityManager.persist(article);
+        Long expectPrimaryKey = 51L;
+        Assert.assertEquals(expectPrimaryKey, article.getId());
+
+        entityManager.getTransaction()
+            .commit();
+    }
+
+    @Test
+    public void givenAutoStrategy_whenPersist_thenReturnPrimaryKey() {
+        Admin admin = new Admin();
+        admin.setName("Test Name");
+
+        entityManager.persist(admin);
+
+        Long expectPrimaryKey = 1L;
+        Assert.assertEquals(expectPrimaryKey, admin.getId());
+    }
+}

persistence-modules/spring-data-elasticsearch/README.md

@@ -6,6 +6,7 @@
 - [Guide to Elasticsearch in Java](https://www.baeldung.com/elasticsearch-java)
 - [Geospatial Support in ElasticSearch](https://www.baeldung.com/elasticsearch-geo-spatial)
 - [A Simple Tagging Implementation with Elasticsearch](https://www.baeldung.com/elasticsearch-tagging)
+- [Introduction to Spring Data Elasticsearch – test 2](https://www.baeldung.com/spring-data-elasticsearch-test-2)
 
 ### Build the Project with Tests Running
 ```

persistence-modules/spring-jpa/README.md

@@ -10,9 +10,9 @@
 - [Self-Contained Testing Using an In-Memory Database](https://www.baeldung.com/spring-jpa-test-in-memory-database)
 - [A Guide to Spring AbstractRoutingDatasource](https://www.baeldung.com/spring-abstract-routing-data-source)
 - [Obtaining Auto-generated Keys in Spring JDBC](https://www.baeldung.com/spring-jdbc-autogenerated-keys)
-- [Transactions with Spring and JPA](https://www.baeldung.com/transaction-configuration-with-jpa-and-spring)
 - [Use Criteria Queries in a Spring Data Application](https://www.baeldung.com/spring-data-criteria-queries)
 - [Many-To-Many Relationship in JPA](https://www.baeldung.com/jpa-many-to-many)
+- [Spring Persistence (Hibernate and JPA) with a JNDI datasource](https://www.baeldung.com/spring-persistence-hibernate-and-jpa-with-a-jndi-datasource-2)
 
 
 ### Eclipse Config 

persistence-modules/spring-persistence-simple-2/README.md

@@ -2,3 +2,4 @@
 
 - [Spring JdbcTemplate Unit Testing](https://www.baeldung.com/spring-jdbctemplate-testing)
 - [Using a List of Values in a JdbcTemplate IN Clause](https://www.baeldung.com/spring-jdbctemplate-in-list)
+- [Transactional Annotations: Spring vs. JTA](https://www.baeldung.com/spring-vs-jta-transactional)

pom.xml

@@ -69,12 +69,6 @@
             <version>${hamcrest-all.version}</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>net.bytebuddy</groupId>
-            <artifactId>byte-buddy</artifactId>
-            <version>${byte-buddy.version}</version>
-            <scope>test</scope>
-        </dependency>
         <dependency>
             <groupId>org.mockito</groupId>
             <artifactId>mockito-core</artifactId>
@@ -1280,7 +1274,7 @@
                 <module>wildfly</module>
                 <module>xml</module>
                 <module>xstream</module>
-                <module>libraries-concurrency</module>
+<!--                <module>libraries-concurrency</module>--> <!-- we haven't upgraded to Java 11 -->
             </modules>
 
         </profile>

spring-boot-modules/spring-boot-ci-cd/README.md

@@ -4,4 +4,4 @@ This module contains articles about CI/CD with Spring Boot
 
 ## Relevant Articles
 
-- [CI/CD for a Spring Boot Project](https://www.baeldung.com/spring-boot-ci-cd)
+- [Applying CI/CD With Spring Boot](https://www.baeldung.com/spring-boot-ci-cd)

spring-boot-modules/spring-boot-crud/src/main/java/com/baeldung/crud/controllers/UserController.java

@@ -36,7 +36,7 @@ public class UserController {
         
         userRepository.save(user);
         model.addAttribute("users", userRepository.findAll());
-        return "index";
+        return "redirect:/index";
     }
     
     @GetMapping("/edit/{id}")
@@ -55,7 +55,7 @@ public class UserController {
         
         userRepository.save(user);
         model.addAttribute("users", userRepository.findAll());
-        return "index";
+        return "redirect:/index";
     }
     
     @GetMapping("/delete/{id}")

spring-boot-modules/spring-boot-crud/src/test/java/com/baeldung/crud/UserControllerUnitTest.java

@@ -41,7 +41,7 @@ public class UserControllerUnitTest {
 
         when(mockedBindingResult.hasErrors()).thenReturn(false);
 
-        assertThat(userController.addUser(user, mockedBindingResult, mockedModel)).isEqualTo("index");
+        assertThat(userController.addUser(user, mockedBindingResult, mockedModel)).isEqualTo("redirect:/index");
     }
 
     @Test
@@ -64,7 +64,7 @@ public class UserControllerUnitTest {
 
         when(mockedBindingResult.hasErrors()).thenReturn(false);
 
-        assertThat(userController.updateUser(1l, user, mockedBindingResult, mockedModel)).isEqualTo("index");
+        assertThat(userController.updateUser(1l, user, mockedBindingResult, mockedModel)).isEqualTo("redirect:/index");
     }
 
     @Test

spring-boot-modules/spring-boot-mvc-3/README.md

@@ -0,0 +1,7 @@
+## Spring Boot MVC
+
+This module contains articles about Spring Web MVC in Spring Boot projects.
+
+### Relevant Articles:
+
+- More articles: [[prev -->]](/spring-boot-modules/spring-boot-mvc-2)

spring-boot-modules/spring-boot-mvc-3/pom.xml

@@ -0,0 +1,29 @@
+<?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>spring-boot-mvc-3</artifactId>
+    <name>spring-boot-mvc-3</name>
+    <packaging>jar</packaging>
+    <description>Module For Spring Boot MVC Web</description>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-boot-2</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-boot-2</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-thymeleaf</artifactId>
+        </dependency>
+    </dependencies>
+
+</project>

spring-boot-modules/spring-boot-mvc-3/src/main/java/com/baeldung/circularviewpath/CircularViewPathApplication.java

@@ -0,0 +1,21 @@
+package com.baeldung.circularviewpath;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/**
+ * Spring Boot launcher for an application
+ *
+ */
+@SpringBootApplication(scanBasePackages = "com.baeldung.controller.circularviewpath")
+public class CircularViewPathApplication {
+
+    /**
+     * Launches a Spring Boot application
+     *
+     * @param args null
+     */
+    public static void main(String[] args) {
+        SpringApplication.run(CircularViewPathApplication.class, args);
+    }
+}

spring-boot-modules/spring-boot-mvc-3/src/main/java/com/baeldung/controller/circularviewpath/CircularViewPathController.java

@@ -0,0 +1,16 @@
+package com.baeldung.controller.circularviewpath;
+
+import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.GetMapping;
+
+@Controller
+public class CircularViewPathController {
+
+    /**
+     * A request mapping which may cause circular view path exception
+     */
+    @GetMapping("/path")
+    public String path() {
+        return "path";
+    }
+}

spring-boot-modules/spring-boot-mvc-3/src/main/resources/logback.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

spring-boot-modules/spring-boot-mvc-3/src/main/resources/templates/path.html

@@ -0,0 +1,13 @@
+<!doctype html>
+
+<html lang="en">
+<head>
+    <meta charset="utf-8">
+
+    <title>path.html</title>
+</head>
+
+<body>
+    <p>path.html</p>
+</body>
+</html>

spring-boot-modules/spring-boot-properties-2/README.md

@@ -7,4 +7,5 @@ This module contains articles about Properties in Spring Boot.
 - [A Quick Guide to Spring @Value](https://www.baeldung.com/spring-value-annotation)
 - [Using Spring @Value with Defaults](https://www.baeldung.com/spring-value-defaults)
 - [How to Inject a Property Value Into a Class Not Managed by Spring?](https://www.baeldung.com/inject-properties-value-non-spring-class)
+- [@PropertySource with YAML Files in Spring Boot](https://www.baeldung.com/spring-yaml-propertysource)
 - More articles: [[<-- prev]](../spring-boot-properties)