Merge branch 'master' into master

.gitignore

@@ -33,3 +33,11 @@ spring-openid/src/main/resources/application.properties
 spring-security-openid/src/main/resources/application.properties
 
 spring-all/*.log
+
+*.jar
+
+SpringDataInjectionDemo/.mvn/wrapper/maven-wrapper.properties
+
+spring-call-getters-using-reflection/.mvn/wrapper/maven-wrapper.properties
+
+spring-check-if-a-property-is-null/.mvn/wrapper/maven-wrapper.properties

akka-streams/README.md

@@ -0,0 +1,3 @@
+### Relevant articles
+
+- [Guide to Akka Streams](http://www.baeldung.com/akka-streams)

akka-streams/pom.xml

@@ -0,0 +1,30 @@
+<?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">
+    <parent>
+        <artifactId>parent-modules</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>akka-streams</artifactId>
+    <name>akka-streams</name>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.typesafe.akka</groupId>
+            <artifactId>akka-stream_2.11</artifactId>
+            <version>${akkastreams.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.typesafe.akka</groupId>
+            <artifactId>akka-stream-testkit_2.11</artifactId>
+            <version>${akkastreams.version}</version>
+        </dependency>
+    </dependencies>
+    <properties>
+        <akkastreams.version>2.5.2</akkastreams.version>
+    </properties>
+
+</project>

akka-streams/src/main/java/com/baeldung/akkastreams/AverageRepository.java

@@ -0,0 +1,14 @@
+package com.baeldung.akkastreams;
+
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionStage;
+
+public class AverageRepository {
+    CompletionStage<Double> save(Double average) {
+        return CompletableFuture.supplyAsync(() -> {
+            System.out.println("saving average: " + average);
+            return average;
+        });
+    }
+}

akka-streams/src/main/java/com/baeldung/akkastreams/DataImporter.java

@@ -0,0 +1,74 @@
+package com.baeldung.akkastreams;
+
+
+import akka.Done;
+import akka.NotUsed;
+import akka.actor.ActorSystem;
+import akka.stream.ActorMaterializer;
+import akka.stream.javadsl.Flow;
+import akka.stream.javadsl.Keep;
+import akka.stream.javadsl.Sink;
+import akka.stream.javadsl.Source;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionStage;
+import java.util.stream.Collectors;
+
+public class DataImporter {
+    private final ActorSystem actorSystem;
+    private final AverageRepository averageRepository = new AverageRepository();
+
+    public DataImporter(ActorSystem actorSystem) {
+        this.actorSystem = actorSystem;
+
+    }
+
+    private List<Integer> parseLine(String line) {
+        String[] fields = line.split(";");
+        return Arrays.stream(fields)
+                .map(Integer::parseInt)
+                .collect(Collectors.toList());
+    }
+
+    private Flow<String, Integer, NotUsed> parseContent() {
+        return Flow.of(String.class).mapConcat(this::parseLine);
+    }
+
+    private Flow<Integer, Double, NotUsed> computeAverage() {
+        return Flow.of(Integer.class).grouped(2).mapAsyncUnordered(8, integers ->
+                CompletableFuture.supplyAsync(() -> integers
+                        .stream()
+                        .mapToDouble(v -> v)
+                        .average()
+                        .orElse(-1.0)));
+    }
+
+    Flow<String, Double, NotUsed> calculateAverage() {
+        return Flow.of(String.class)
+                .via(parseContent())
+                .via(computeAverage());
+    }
+
+    private Sink<Double, CompletionStage<Done>> storeAverages() {
+        return Flow.of(Double.class)
+                .mapAsyncUnordered(4, averageRepository::save)
+                .toMat(Sink.ignore(), Keep.right());
+    }
+
+
+    CompletionStage<Done> calculateAverageForContent(String content) {
+        return Source.single(content)
+                .via(calculateAverage())
+                .runWith(storeAverages(), ActorMaterializer.create(actorSystem))
+                .whenComplete((d, e) -> {
+                    if (d != null) {
+                        System.out.println("Import finished ");
+                    } else {
+                        e.printStackTrace();
+                    }
+                });
+    }
+
+}

akka-streams/src/test/java/com/baeldung/akkastreams/DataImporterUnitTest.java

@@ -0,0 +1,43 @@
+package com.baeldung.akkastreams;
+
+import akka.NotUsed;
+import akka.actor.ActorSystem;
+import akka.stream.ActorMaterializer;
+import akka.stream.javadsl.Flow;
+import akka.stream.javadsl.Source;
+import akka.stream.testkit.javadsl.TestSink;
+import org.junit.Test;
+
+
+public class DataImporterUnitTest {
+    private final ActorSystem actorSystem = ActorSystem.create();
+
+    @Test
+    public void givenStreamOfIntegers_whenCalculateAverageOfPairs_thenShouldReturnProperResults() {
+        //given
+        Flow<String, Double, NotUsed> tested = new DataImporter(actorSystem).calculateAverage();
+        String input = "1;9;11;0";
+
+        //when
+        Source<Double, NotUsed> flow = Source.single(input).via(tested);
+
+        //then
+        flow
+                .runWith(TestSink.probe(actorSystem), ActorMaterializer.create(actorSystem))
+                .request(4)
+                .expectNextUnordered(5d, 5.5);
+    }
+
+    @Test
+    public void givenStreamOfIntegers_whenCalculateAverageAndSaveToSink_thenShouldFinishSuccessfully() {
+        //given
+        DataImporter dataImporter = new DataImporter(actorSystem);
+        String input = "10;90;110;10";
+
+        //when
+        dataImporter.calculateAverageForContent(input)
+                .thenAccept(d -> actorSystem.terminate());
+
+    }
+
+}

algorithms/src/main/java/com/baeldung/algorithms/automata/FiniteStateMachine.java

@@ -1,4 +1,4 @@
-package com.baeldung.automata;
+package com.baeldung.algorithms.automata;
 
 /**
  * Finite state machine.

algorithms/src/main/java/com/baeldung/algorithms/automata/RtFiniteStateMachine.java

@@ -1,4 +1,4 @@
-package com.baeldung.automata;
+package com.baeldung.algorithms.automata;
 
 /**
  * Default implementation of a finite state machine.

algorithms/src/main/java/com/baeldung/algorithms/automata/RtState.java

@@ -1,4 +1,4 @@
-package com.baeldung.automata;
+package com.baeldung.algorithms.automata;
 
 import java.util.ArrayList;
 import java.util.List;

algorithms/src/main/java/com/baeldung/algorithms/automata/RtTransition.java

@@ -1,4 +1,4 @@
-package com.baeldung.automata;
+package com.baeldung.algorithms.automata;
 
 
 /**

algorithms/src/main/java/com/baeldung/algorithms/automata/State.java

@@ -1,4 +1,4 @@
-package com.baeldung.automata;
+package com.baeldung.algorithms.automata;
 
 /**
  * State. Part of a finite state machine.

algorithms/src/main/java/com/baeldung/algorithms/automata/Transition.java

@@ -1,4 +1,4 @@
-package com.baeldung.automata;
+package com.baeldung.algorithms.automata;
 
 /**
  * Transition in a finite State machine.

algorithms/src/main/java/com/baeldung/algorithms/hillclimbing/HillClimbing.java

@@ -0,0 +1,189 @@
+package com.baeldung.algorithms.hillclimbing;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Stack;
+
+public class HillClimbing {
+    public static void main(String[] args) {
+        HillClimbing hillClimbing = new HillClimbing();
+        String blockArr[] = { "B", "C", "D", "A" };
+        Stack<String> startState = hillClimbing.getStackWithValues(blockArr);
+        String goalBlockArr[] = { "A", "B", "C", "D" };
+        Stack<String> goalState = hillClimbing.getStackWithValues(goalBlockArr);
+        try {
+            List<State> solutionSequence = hillClimbing.getRouteWithHillClimbing(startState, goalState);
+            solutionSequence.forEach(HillClimbing::printEachStep);
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    private static void printEachStep(State state) {
+        List<Stack<String>> stackList = state.getState();
+        System.out.println("----------------");
+        stackList.forEach(stack -> {
+            while (!stack.isEmpty()) {
+                System.out.println(stack.pop());
+            }
+            System.out.println(" ");
+        });
+    }
+
+    private Stack<String> getStackWithValues(String[] blocks) {
+        Stack<String> stack = new Stack<>();
+        for (String block : blocks)
+            stack.push(block);
+        return stack;
+    }
+
+    /**
+     * This method prepares path from init state to goal state
+     */
+    public List<State> getRouteWithHillClimbing(Stack<String> initStateStack, Stack<String> goalStateStack) throws Exception {
+        List<Stack<String>> initStateStackList = new ArrayList<>();
+        initStateStackList.add(initStateStack);
+        int initStateHeuristics = getHeuristicsValue(initStateStackList, goalStateStack);
+        State initState = new State(initStateStackList, initStateHeuristics);
+
+        List<State> resultPath = new ArrayList<>();
+        resultPath.add(new State(initState));
+
+        State currentState = initState;
+        boolean noStateFound = false;
+        while (!currentState.getState()
+            .get(0)
+            .equals(goalStateStack) || noStateFound) {
+            noStateFound = true;
+            State nextState = findNextState(currentState, goalStateStack);
+            if (nextState != null) {
+                noStateFound = false;
+                currentState = nextState;
+                resultPath.add(new State(nextState));
+            }
+        }
+
+        return resultPath;
+    }
+
+    /**
+     * This method finds new state from current state based on goal and
+     * heuristics
+     */
+    public State findNextState(State currentState, Stack<String> goalStateStack) {
+        List<Stack<String>> listOfStacks = currentState.getState();
+        int currentStateHeuristics = currentState.getHeuristics();
+
+        return listOfStacks.stream()
+            .map(stack -> {
+                return applyOperationsOnState(listOfStacks, stack, currentStateHeuristics, goalStateStack);
+            })
+            .filter(Objects::nonNull)
+            .findFirst()
+          .orElse(null);
+    }
+
+    /**
+     * This method applies operations on the current state to get a new state
+     */
+    public State applyOperationsOnState(List<Stack<String>> listOfStacks, Stack<String> stack, int currentStateHeuristics, Stack<String> goalStateStack) {
+        State tempState;
+        List<Stack<String>> tempStackList = new ArrayList<>(listOfStacks);
+        String block = stack.pop();
+        if (stack.size() == 0)
+            tempStackList.remove(stack);
+        tempState = pushElementToNewStack(tempStackList, block, currentStateHeuristics, goalStateStack);
+        if (tempState == null) {
+            tempState = pushElementToExistingStacks(stack, tempStackList, block, currentStateHeuristics, goalStateStack);
+        }
+        if (tempState == null)
+            stack.push(block);
+        return tempState;
+    }
+    
+    /**
+     * Operation to be applied on a state in order to find new states. This
+     * operation pushes an element into a new stack
+     */
+    private State pushElementToNewStack(List<Stack<String>> currentStackList, String block, int currentStateHeuristics, Stack<String> goalStateStack) {
+        State newState = null;
+        Stack<String> newStack = new Stack<>();
+        newStack.push(block);
+
+        currentStackList.add(newStack);
+        int newStateHeuristics = getHeuristicsValue(currentStackList, goalStateStack);
+        if (newStateHeuristics > currentStateHeuristics) {
+            newState = new State(currentStackList, newStateHeuristics);
+        } else {
+            currentStackList.remove(newStack);
+        }
+        return newState;
+    }
+
+    /**
+     * Operation to be applied on a state in order to find new states. This
+     * operation pushes an element into one of the other stacks to explore new
+     * states
+     */
+    private State pushElementToExistingStacks(Stack currentStack, List<Stack<String>> currentStackList, String block, int currentStateHeuristics, Stack<String> goalStateStack) {
+
+        Optional<State> newState = currentStackList.stream()
+            .filter(stack -> stack != currentStack)
+            .map(stack -> {
+                return pushElementToStack(stack, block, currentStackList, currentStateHeuristics, goalStateStack);
+            })
+            .filter(Objects::nonNull)
+            .findFirst();
+
+        return newState.orElse(null);
+    }
+    
+    /**
+     * This method pushes a block to the stack and returns new state if its closer to goal
+     */
+    private State pushElementToStack(Stack stack, String block, List<Stack<String>> currentStackList, int currentStateHeuristics, Stack<String> goalStateStack) {
+        stack.push(block);
+        int newStateHeuristics = getHeuristicsValue(currentStackList, goalStateStack);
+        if (newStateHeuristics > currentStateHeuristics) {
+            return new State(currentStackList, newStateHeuristics);
+        }
+        stack.pop();
+        return null;
+    }
+
+    /**
+     * This method returns heuristics value for given state with respect to goal
+     * state
+     */
+    public int getHeuristicsValue(List<Stack<String>> currentState, Stack<String> goalStateStack) {
+        Integer heuristicValue;
+        heuristicValue = currentState.stream()
+            .mapToInt(stack -> {
+                return getHeuristicsValueForStack(stack, currentState, goalStateStack);
+            })
+            .sum();
+        return heuristicValue;
+    }
+    
+    /**
+     * This method returns heuristics value for a particular stack
+     */
+    public int getHeuristicsValueForStack(Stack<String> stack, List<Stack<String>> currentState, Stack<String> goalStateStack) {
+        int stackHeuristics = 0;
+        boolean isPositioneCorrect = true;
+        int goalStartIndex = 0;
+        for (String currentBlock : stack) {
+            if (isPositioneCorrect && currentBlock.equals(goalStateStack.get(goalStartIndex))) {
+                stackHeuristics += goalStartIndex;
+            } else {
+                stackHeuristics -= goalStartIndex;
+                isPositioneCorrect = false;
+            }
+            goalStartIndex++;
+        }
+        return stackHeuristics;
+    }
+
+}

algorithms/src/main/java/com/baeldung/algorithms/hillclimbing/State.java

@@ -0,0 +1,43 @@
+package com.baeldung.algorithms.hillclimbing;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Stack;
+
+public class State {
+    private List<Stack<String>> state;
+    private int heuristics;
+
+    public State(List<Stack<String>> state) {
+        this.state = state;
+    }
+
+    State(List<Stack<String>> state, int heuristics) {
+        this.state = state;
+        this.heuristics = heuristics;
+    }
+
+    State(State state) {
+        if (state != null) {
+            this.state = new ArrayList<>();
+            for (Stack s : state.getState()) {
+                Stack s1;
+                s1 = (Stack) s.clone();
+                this.state.add(s1);
+            }
+            this.heuristics = state.getHeuristics();
+        }
+    }
+
+    public List<Stack<String>> getState() {
+        return state;
+    }
+
+    public int getHeuristics() {
+        return heuristics;
+    }
+
+    public void setHeuristics(int heuristics) {
+        this.heuristics = heuristics;
+    }
+}

algorithms/src/main/java/com/baeldung/algorithms/mcts/montecarlo/MonteCarloTreeSearch.java

@@ -0,0 +1,109 @@
+package com.baeldung.algorithms.mcts.montecarlo;
+
+import java.util.List;
+
+import com.baeldung.algorithms.mcts.tictactoe.Board;
+import com.baeldung.algorithms.mcts.tree.Node;
+import com.baeldung.algorithms.mcts.tree.Tree;
+
+public class MonteCarloTreeSearch {
+
+    private static final int WIN_SCORE = 10;
+    private int level;
+    private int oponent;
+
+    public MonteCarloTreeSearch() {
+        this.level = 3;
+    }
+
+    public int getLevel() {
+        return level;
+    }
+
+    public void setLevel(int level) {
+        this.level = level;
+    }
+
+    private int getMillisForCurrentLevel() {
+        return 2 * (this.level - 1) + 1;
+    }
+
+    public Board findNextMove(Board board, int playerNo) {
+        long start = System.currentTimeMillis();
+        long end = start + 60 * getMillisForCurrentLevel();
+
+        oponent = 3 - playerNo;
+        Tree tree = new Tree();
+        Node rootNode = tree.getRoot();
+        rootNode.getState().setBoard(board);
+        rootNode.getState().setPlayerNo(oponent);
+
+        while (System.currentTimeMillis() < end) {
+            // Phase 1 - Selection
+            Node promisingNode = selectPromisingNode(rootNode);
+            // Phase 2 - Expansion
+            if (promisingNode.getState().getBoard().checkStatus() == Board.IN_PROGRESS)
+                expandNode(promisingNode);
+
+            // Phase 3 - Simulation
+            Node nodeToExplore = promisingNode;
+            if (promisingNode.getChildArray().size() > 0) {
+                nodeToExplore = promisingNode.getRandomChildNode();
+            }
+            int playoutResult = simulateRandomPlayout(nodeToExplore);
+            // Phase 4 - Update
+            backPropogation(nodeToExplore, playoutResult);
+        }
+
+        Node winnerNode = rootNode.getChildWithMaxScore();
+        tree.setRoot(winnerNode);
+        return winnerNode.getState().getBoard();
+    }
+
+    private Node selectPromisingNode(Node rootNode) {
+        Node node = rootNode;
+        while (node.getChildArray().size() != 0) {
+            node = UCT.findBestNodeWithUCT(node);
+        }
+        return node;
+    }
+
+    private void expandNode(Node node) {
+        List<State> possibleStates = node.getState().getAllPossibleStates();
+        possibleStates.forEach(state -> {
+            Node newNode = new Node(state);
+            newNode.setParent(node);
+            newNode.getState().setPlayerNo(node.getState().getOpponent());
+            node.getChildArray().add(newNode);
+        });
+    }
+
+    private void backPropogation(Node nodeToExplore, int playerNo) {
+        Node tempNode = nodeToExplore;
+        while (tempNode != null) {
+            tempNode.getState().incrementVisit();
+            if (tempNode.getState().getPlayerNo() == playerNo)
+                tempNode.getState().addScore(WIN_SCORE);
+            tempNode = tempNode.getParent();
+        }
+    }
+
+    private int simulateRandomPlayout(Node node) {
+        Node tempNode = new Node(node);
+        State tempState = tempNode.getState();
+        int boardStatus = tempState.getBoard().checkStatus();
+
+        if (boardStatus == oponent) {
+            tempNode.getParent().getState().setWinScore(Integer.MIN_VALUE);
+            return boardStatus;
+        }
+        while (boardStatus == Board.IN_PROGRESS) {
+            tempState.togglePlayer();
+            tempState.randomPlay();
+            boardStatus = tempState.getBoard().checkStatus();
+        }
+
+        return boardStatus;
+    }
+
+}

algorithms/src/main/java/com/baeldung/algorithms/mcts/montecarlo/State.java

@@ -0,0 +1,97 @@
+package com.baeldung.algorithms.mcts.montecarlo;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import com.baeldung.algorithms.mcts.tictactoe.Board;
+import com.baeldung.algorithms.mcts.tictactoe.Position;
+
+public class State {
+    private Board board;
+    private int playerNo;
+    private int visitCount;
+    private double winScore;
+
+    public State() {
+        board = new Board();
+    }
+
+    public State(State state) {
+        this.board = new Board(state.getBoard());
+        this.playerNo = state.getPlayerNo();
+        this.visitCount = state.getVisitCount();
+        this.winScore = state.getWinScore();
+    }
+
+    public State(Board board) {
+        this.board = new Board(board);
+    }
+
+    Board getBoard() {
+        return board;
+    }
+
+    void setBoard(Board board) {
+        this.board = board;
+    }
+
+    int getPlayerNo() {
+        return playerNo;
+    }
+
+    void setPlayerNo(int playerNo) {
+        this.playerNo = playerNo;
+    }
+
+    int getOpponent() {
+        return 3 - playerNo;
+    }
+
+    public int getVisitCount() {
+        return visitCount;
+    }
+
+    public void setVisitCount(int visitCount) {
+        this.visitCount = visitCount;
+    }
+
+    double getWinScore() {
+        return winScore;
+    }
+
+    void setWinScore(double winScore) {
+        this.winScore = winScore;
+    }
+
+    public List<State> getAllPossibleStates() {
+        List<State> possibleStates = new ArrayList<>();
+        List<Position> availablePositions = this.board.getEmptyPositions();
+        availablePositions.forEach(p -> {
+            State newState = new State(this.board);
+            newState.setPlayerNo(3 - this.playerNo);
+            newState.getBoard().performMove(newState.getPlayerNo(), p);
+            possibleStates.add(newState);
+        });
+        return possibleStates;
+    }
+
+    void incrementVisit() {
+        this.visitCount++;
+    }
+
+    void addScore(double score) {
+        if (this.winScore != Integer.MIN_VALUE)
+            this.winScore += score;
+    }
+
+    void randomPlay() {
+        List<Position> availablePositions = this.board.getEmptyPositions();
+        int totalPossibilities = availablePositions.size();
+        int selectRandom = (int) (Math.random() * ((totalPossibilities - 1) + 1));
+        this.board.performMove(this.playerNo, availablePositions.get(selectRandom));
+    }
+
+    void togglePlayer() {
+        this.playerNo = 3 - this.playerNo;
+    }
+}

algorithms/src/main/java/com/baeldung/algorithms/mcts/montecarlo/UCT.java

@@ -0,0 +1,24 @@
+package com.baeldung.algorithms.mcts.montecarlo;
+
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+import com.baeldung.algorithms.mcts.tree.Node;
+
+public class UCT {
+
+    public static double uctValue(int totalVisit, double nodeWinScore, int nodeVisit) {
+        if (nodeVisit == 0) {
+            return Integer.MAX_VALUE;
+        }
+        return (nodeWinScore / (double) nodeVisit) + 1.41 * Math.sqrt(Math.log(totalVisit) / (double) nodeVisit);
+    }
+
+    static Node findBestNodeWithUCT(Node node) {
+        int parentVisit = node.getState().getVisitCount();
+        return Collections.max(
+          node.getChildArray(),
+          Comparator.comparing(c -> uctValue(parentVisit, c.getState().getWinScore(), c.getState().getVisitCount())));
+    }
+}

algorithms/src/main/java/com/baeldung/algorithms/mcts/tictactoe/Board.java

@@ -0,0 +1,155 @@
+package com.baeldung.algorithms.mcts.tictactoe;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class Board {
+    int[][] boardValues;
+    int totalMoves;
+
+    public static final int DEFAULT_BOARD_SIZE = 3;
+
+    public static final int IN_PROGRESS = -1;
+    public static final int DRAW = 0;
+    public static final int P1 = 1;
+    public static final int P2 = 2;
+
+    public Board() {
+        boardValues = new int[DEFAULT_BOARD_SIZE][DEFAULT_BOARD_SIZE];
+    }
+
+    public Board(int boardSize) {
+        boardValues = new int[boardSize][boardSize];
+    }
+
+    public Board(int[][] boardValues) {
+        this.boardValues = boardValues;
+    }
+
+    public Board(int[][] boardValues, int totalMoves) {
+        this.boardValues = boardValues;
+        this.totalMoves = totalMoves;
+    }
+
+    public Board(Board board) {
+        int boardLength = board.getBoardValues().length;
+        this.boardValues = new int[boardLength][boardLength];
+        int[][] boardValues = board.getBoardValues();
+        int n = boardValues.length;
+        for (int i = 0; i < n; i++) {
+            int m = boardValues[i].length;
+            for (int j = 0; j < m; j++) {
+                this.boardValues[i][j] = boardValues[i][j];
+            }
+        }
+    }
+
+    public void performMove(int player, Position p) {
+        this.totalMoves++;
+        boardValues[p.getX()][p.getY()] = player;
+    }
+
+    public int[][] getBoardValues() {
+        return boardValues;
+    }
+
+    public void setBoardValues(int[][] boardValues) {
+        this.boardValues = boardValues;
+    }
+
+    public int checkStatus() {
+        int boardSize = boardValues.length;
+        int maxIndex = boardSize - 1;
+        int[] diag1 = new int[boardSize];
+        int[] diag2 = new int[boardSize];
+        
+        for (int i = 0; i < boardSize; i++) {
+            int[] row = boardValues[i];
+            int[] col = new int[boardSize];
+            for (int j = 0; j < boardSize; j++) {
+                col[j] = boardValues[j][i];
+            }
+            
+            int checkRowForWin = checkForWin(row);
+            if(checkRowForWin!=0)
+                return checkRowForWin;
+            
+            int checkColForWin = checkForWin(col);
+            if(checkColForWin!=0)
+                return checkColForWin;
+            
+            diag1[i] = boardValues[i][i];
+            diag2[i] = boardValues[maxIndex - i][i];
+        }
+
+        int checkDia1gForWin = checkForWin(diag1);
+        if(checkDia1gForWin!=0)
+            return checkDia1gForWin;
+        
+        int checkDiag2ForWin = checkForWin(diag2);
+        if(checkDiag2ForWin!=0)
+            return checkDiag2ForWin;
+        
+        if (getEmptyPositions().size() > 0)
+            return IN_PROGRESS;
+        else
+            return DRAW;
+    }
+
+    private int checkForWin(int[] row) {
+        boolean isEqual = true;
+        int size = row.length;
+        int previous = row[0];
+        for (int i = 0; i < size; i++) {
+            if (previous != row[i]) {
+                isEqual = false;
+                break;
+            }
+            previous = row[i];
+        }
+        if(isEqual)
+            return previous;
+        else
+            return 0;
+    }
+
+    public void printBoard() {
+        int size = this.boardValues.length;
+        for (int i = 0; i < size; i++) {
+            for (int j = 0; j < size; j++) {
+                System.out.print(boardValues[i][j] + " ");
+            }
+            System.out.println();
+        }
+    }
+
+    public List<Position> getEmptyPositions() {
+        int size = this.boardValues.length;
+        List<Position> emptyPositions = new ArrayList<>();
+        for (int i = 0; i < size; i++) {
+            for (int j = 0; j < size; j++) {
+                if (boardValues[i][j] == 0)
+                    emptyPositions.add(new Position(i, j));
+            }
+        }
+        return emptyPositions;
+    }
+
+    public void printStatus() {
+        switch (this.checkStatus()) {
+        case P1:
+            System.out.println("Player 1 wins");
+            break;
+        case P2:
+            System.out.println("Player 2 wins");
+            break;
+        case DRAW:
+            System.out.println("Game Draw");
+            break;
+        case IN_PROGRESS:
+            System.out.println("Game In rogress");
+            break;
+        }
+    }
+}

algorithms/src/main/java/com/baeldung/algorithms/mcts/tictactoe/Position.java

@@ -0,0 +1,31 @@
+package com.baeldung.algorithms.mcts.tictactoe;
+
+public class Position {
+    int x;
+    int y;
+
+    public Position() {
+    }
+
+    public Position(int x, int y) {
+        this.x = x;
+        this.y = y;
+    }
+
+    public int getX() {
+        return x;
+    }
+
+    public void setX(int x) {
+        this.x = x;
+    }
+
+    public int getY() {
+        return y;
+    }
+
+    public void setY(int y) {
+        this.y = y;
+    }
+
+}

algorithms/src/main/java/com/baeldung/algorithms/mcts/tree/Node.java

@@ -0,0 +1,78 @@
+package com.baeldung.algorithms.mcts.tree;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+import com.baeldung.algorithms.mcts.montecarlo.State;
+
+public class Node {
+    State state;
+    Node parent;
+    List<Node> childArray;
+
+    public Node() {
+        this.state = new State();
+        childArray = new ArrayList<>();
+    }
+
+    public Node(State state) {
+        this.state = state;
+        childArray = new ArrayList<>();
+    }
+
+    public Node(State state, Node parent, List<Node> childArray) {
+        this.state = state;
+        this.parent = parent;
+        this.childArray = childArray;
+    }
+
+    public Node(Node node) {
+        this.childArray = new ArrayList<>();
+        this.state = new State(node.getState());
+        if (node.getParent() != null)
+            this.parent = node.getParent();
+        List<Node> childArray = node.getChildArray();
+        for (Node child : childArray) {
+            this.childArray.add(new Node(child));
+        }
+    }
+
+    public State getState() {
+        return state;
+    }
+
+    public void setState(State state) {
+        this.state = state;
+    }
+
+    public Node getParent() {
+        return parent;
+    }
+
+    public void setParent(Node parent) {
+        this.parent = parent;
+    }
+
+    public List<Node> getChildArray() {
+        return childArray;
+    }
+
+    public void setChildArray(List<Node> childArray) {
+        this.childArray = childArray;
+    }
+
+    public Node getRandomChildNode() {
+        int noOfPossibleMoves = this.childArray.size();
+        int selectRandom = (int) (Math.random() * ((noOfPossibleMoves - 1) + 1));
+        return this.childArray.get(selectRandom);
+    }
+
+    public Node getChildWithMaxScore() {
+        return Collections.max(this.childArray, Comparator.comparing(c -> {
+            return c.getState().getVisitCount();
+        }));
+    }
+
+}

algorithms/src/main/java/com/baeldung/algorithms/mcts/tree/Tree.java

@@ -0,0 +1,26 @@
+package com.baeldung.algorithms.mcts.tree;
+
+public class Tree {
+    Node root;
+
+    public Tree() {
+        root = new Node();
+    }
+
+    public Tree(Node root) {
+        this.root = root;
+    }
+
+    public Node getRoot() {
+        return root;
+    }
+
+    public void setRoot(Node root) {
+        this.root = root;
+    }
+
+    public void addChild(Node parent, Node child) {
+        parent.getChildArray().add(child);
+    }
+
+}

algorithms/src/main/java/com/baeldung/algorithms/minimax/GameOfBones.java

@@ -0,0 +1,14 @@
+package com.baeldung.algorithms.minimax;
+
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+class GameOfBones {
+    static List<Integer> getPossibleStates(int noOfBonesInHeap) {
+        return IntStream.rangeClosed(1, 3).boxed()
+          .map(i -> noOfBonesInHeap - i)
+          .filter(newHeapCount -> newHeapCount >= 0)
+          .collect(Collectors.toList());
+    }
+}

algorithms/src/main/java/com/baeldung/algorithms/minimax/MiniMax.java

@@ -0,0 +1,60 @@
+package com.baeldung.algorithms.minimax;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+public class MiniMax {
+    private Tree tree;
+
+    public Tree getTree() {
+        return tree;
+    }
+
+    public void constructTree(int noOfBones) {
+        tree = new Tree();
+        Node root = new Node(noOfBones, true);
+        tree.setRoot(root);
+        constructTree(root);
+    }
+
+    private void constructTree(Node node) {
+        List<Integer> listofPossibleHeaps = GameOfBones.getPossibleStates(node.getNoOfBones());
+        boolean isMaxPlayer = !node.isMaxPlayer();
+        listofPossibleHeaps.forEach(n -> {
+            Node newNode = new Node(n, isMaxPlayer);
+            node.addChild(newNode);
+            if (newNode.getNoOfBones() > 0) {
+                constructTree(newNode);
+            }
+        });
+    }
+
+    public boolean checkWin() {
+        Node root = tree.getRoot();
+        checkWin(root);
+        return root.getScore() == 1;
+    }
+
+    private void checkWin(Node node) {
+        List<Node> children = node.getChildren();
+        boolean isMaxPlayer = node.isMaxPlayer();
+        children.forEach(child -> {
+            if (child.getNoOfBones() == 0) {
+                child.setScore(isMaxPlayer ? 1 : -1);
+            } else {
+                checkWin(child);
+            }
+        });
+        Node bestChild = findBestChild(isMaxPlayer, children);
+        node.setScore(bestChild.getScore());
+    }
+
+    private Node findBestChild(boolean isMaxPlayer, List<Node> children) {
+        Comparator<Node> byScoreComparator = Comparator.comparing(Node::getScore);
+
+        return children.stream()
+          .max(isMaxPlayer ? byScoreComparator : byScoreComparator.reversed())
+          .orElseThrow(NoSuchElementException::new);
+    }
+}

algorithms/src/main/java/com/baeldung/algorithms/minimax/Node.java

@@ -0,0 +1,42 @@
+package com.baeldung.algorithms.minimax;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Node {
+    private int noOfBones;
+    private boolean isMaxPlayer;
+    private int score;
+    private List<Node> children;
+
+    public Node(int noOfBones, boolean isMaxPlayer) {
+        this.noOfBones = noOfBones;
+        this.isMaxPlayer = isMaxPlayer;
+        children = new ArrayList<>();
+    }
+
+    int getNoOfBones() {
+        return noOfBones;
+    }
+
+    boolean isMaxPlayer() {
+        return isMaxPlayer;
+    }
+
+    int getScore() {
+        return score;
+    }
+
+    void setScore(int score) {
+        this.score = score;
+    }
+
+    List<Node> getChildren() {
+        return children;
+    }
+
+    void addChild(Node newNode) {
+        children.add(newNode);
+    }
+
+}

algorithms/src/main/java/com/baeldung/algorithms/minimax/Tree.java

@@ -0,0 +1,16 @@
+package com.baeldung.algorithms.minimax;
+
+public class Tree {
+    private Node root;
+
+    Tree() {
+    }
+
+    Node getRoot() {
+        return root;
+    }
+
+    void setRoot(Node root) {
+        this.root = root;
+    }
+}

algorithms/src/test/java/algorithms/HillClimbingAlgorithmTest.java

@@ -0,0 +1,58 @@
+package algorithms;
+
+import com.baeldung.algorithms.hillclimbing.HillClimbing;
+import com.baeldung.algorithms.hillclimbing.State;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Stack;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+public class HillClimbingAlgorithmTest {
+    private Stack<String> initStack;
+    private Stack<String> goalStack;
+
+    @Before
+    public void initStacks() {
+        String blockArr[] = { "B", "C", "D", "A" };
+        String goalBlockArr[] = { "A", "B", "C", "D" };
+        initStack = new Stack<>();
+        for (String block : blockArr)
+            initStack.push(block);
+        goalStack = new Stack<>();
+        for (String block : goalBlockArr)
+            goalStack.push(block);
+    }
+
+    @Test
+    public void givenInitAndGoalState_whenGetPathWithHillClimbing_thenPathFound() {
+        HillClimbing hillClimbing = new HillClimbing();
+
+        List<State> path;
+        try {
+            path = hillClimbing.getRouteWithHillClimbing(initStack, goalStack);
+            assertNotNull(path);
+            assertEquals(path.get(path.size() - 1)
+                .getState()
+                .get(0), goalStack);
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    @Test
+    public void givenCurrentState_whenFindNextState_thenBetterHeuristics() {
+        HillClimbing hillClimbing = new HillClimbing();
+        List<Stack<String>> initList = new ArrayList<>();
+        initList.add(initStack);
+        State currentState = new State(initList);
+        currentState.setHeuristics(hillClimbing.getHeuristicsValue(initList, goalStack));
+        State nextState = hillClimbing.findNextState(currentState, goalStack);
+        assertTrue(nextState.getHeuristics() > currentState.getHeuristics());
+    }
+}

algorithms/src/test/java/algorithms/MCTSTest.java

@@ -0,0 +1,92 @@
+package algorithms;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.util.List;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import com.baeldung.algorithms.mcts.montecarlo.MonteCarloTreeSearch;
+import com.baeldung.algorithms.mcts.montecarlo.State;
+import com.baeldung.algorithms.mcts.montecarlo.UCT;
+import com.baeldung.algorithms.mcts.tictactoe.Board;
+import com.baeldung.algorithms.mcts.tictactoe.Position;
+import com.baeldung.algorithms.mcts.tree.Tree;
+
+public class MCTSTest {
+    Tree gameTree;
+    MonteCarloTreeSearch mcts;
+
+    @Before
+    public void initGameTree() {
+        gameTree = new Tree();
+        mcts = new MonteCarloTreeSearch();
+    }
+
+    @Test
+    public void givenStats_whenGetUCTForNode_thenUCTMatchesWithManualData() {
+        double uctValue = 15.79;
+        assertEquals(UCT.uctValue(600, 300, 20), uctValue, 0.01);
+    }
+
+    @Test
+    public void giveninitBoardState_whenGetAllPossibleStates_thenNonEmptyList() {
+        State initState = gameTree.getRoot().getState();
+        List<State> possibleStates = initState.getAllPossibleStates();
+        assertTrue(possibleStates.size() > 0);
+    }
+
+    @Test
+    public void givenEmptyBoard_whenPerformMove_thenLessAvailablePossitions() {
+        Board board = new Board();
+        int initAvailablePositions = board.getEmptyPositions().size();
+        board.performMove(Board.P1, new Position(1, 1));
+        int availablePositions = board.getEmptyPositions().size();
+        assertTrue(initAvailablePositions > availablePositions);
+    }
+
+    @Test
+    public void givenEmptyBoard_whenSimulateInterAIPlay_thenGameDraw() {
+        Board board = new Board();
+
+        int player = Board.P1;
+        int totalMoves = Board.DEFAULT_BOARD_SIZE * Board.DEFAULT_BOARD_SIZE;
+        for (int i = 0; i < totalMoves; i++) {
+            board = mcts.findNextMove(board, player);
+            if (board.checkStatus() != -1) {
+                break;
+            }
+            player = 3 - player;
+        }
+        int winStatus = board.checkStatus();
+        assertEquals(winStatus, Board.DRAW);
+    }
+
+    @Test
+    public void givenEmptyBoard_whenLevel1VsLevel3_thenLevel3WinsOrDraw() {
+        Board board = new Board();
+        MonteCarloTreeSearch mcts1 = new MonteCarloTreeSearch();
+        mcts1.setLevel(1);
+        MonteCarloTreeSearch mcts3 = new MonteCarloTreeSearch();
+        mcts3.setLevel(3);
+
+        int player = Board.P1;
+        int totalMoves = Board.DEFAULT_BOARD_SIZE * Board.DEFAULT_BOARD_SIZE;
+        for (int i = 0; i < totalMoves; i++) {
+            if (player == Board.P1)
+                board = mcts3.findNextMove(board, player);
+            else
+                board = mcts1.findNextMove(board, player);
+
+            if (board.checkStatus() != -1) {
+                break;
+            }
+            player = 3 - player;
+        }
+        int winStatus = board.checkStatus();
+        assertTrue(winStatus == Board.DRAW || winStatus == Board.P1);
+    }
+
+}

algorithms/src/test/java/algorithms/RtFiniteStateMachineLongRunningUnitTest.java

@@ -1,6 +1,6 @@
 package algorithms;
 
-import com.baeldung.automata.*;
+import com.baeldung.algorithms.automata.*;
 import org.junit.Test;
 
 import static org.junit.Assert.assertTrue;

algorithms/src/test/java/algorithms/mcts/MCTSTest.java

@@ -0,0 +1,92 @@
+package algorithms.mcts;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.util.List;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import com.baeldung.algorithms.mcts.montecarlo.MonteCarloTreeSearch;
+import com.baeldung.algorithms.mcts.montecarlo.State;
+import com.baeldung.algorithms.mcts.montecarlo.UCT;
+import com.baeldung.algorithms.mcts.tictactoe.Board;
+import com.baeldung.algorithms.mcts.tictactoe.Position;
+import com.baeldung.algorithms.mcts.tree.Tree;
+
+public class MCTSTest {
+    private Tree gameTree;
+    private MonteCarloTreeSearch mcts;
+
+    @Before
+    public void initGameTree() {
+        gameTree = new Tree();
+        mcts = new MonteCarloTreeSearch();
+    }
+
+    @Test
+    public void givenStats_whenGetUCTForNode_thenUCTMatchesWithManualData() {
+        double uctValue = 15.79;
+        assertEquals(UCT.uctValue(600, 300, 20), uctValue, 0.01);
+    }
+
+    @Test
+    public void giveninitBoardState_whenGetAllPossibleStates_thenNonEmptyList() {
+        State initState = gameTree.getRoot().getState();
+        List<State> possibleStates = initState.getAllPossibleStates();
+        assertTrue(possibleStates.size() > 0);
+    }
+
+    @Test
+    public void givenEmptyBoard_whenPerformMove_thenLessAvailablePossitions() {
+        Board board = new Board();
+        int initAvailablePositions = board.getEmptyPositions().size();
+        board.performMove(Board.P1, new Position(1, 1));
+        int availablePositions = board.getEmptyPositions().size();
+        assertTrue(initAvailablePositions > availablePositions);
+    }
+
+    @Test
+    public void givenEmptyBoard_whenSimulateInterAIPlay_thenGameDraw() {
+        Board board = new Board();
+
+        int player = Board.P1;
+        int totalMoves = Board.DEFAULT_BOARD_SIZE * Board.DEFAULT_BOARD_SIZE;
+        for (int i = 0; i < totalMoves; i++) {
+            board = mcts.findNextMove(board, player);
+            if (board.checkStatus() != -1) {
+                break;
+            }
+            player = 3 - player;
+        }
+        int winStatus = board.checkStatus();
+        assertEquals(winStatus, Board.DRAW);
+    }
+
+    @Test
+    public void givenEmptyBoard_whenLevel1VsLevel3_thenLevel3WinsOrDraw() {
+        Board board = new Board();
+        MonteCarloTreeSearch mcts1 = new MonteCarloTreeSearch();
+        mcts1.setLevel(1);
+        MonteCarloTreeSearch mcts3 = new MonteCarloTreeSearch();
+        mcts3.setLevel(3);
+
+        int player = Board.P1;
+        int totalMoves = Board.DEFAULT_BOARD_SIZE * Board.DEFAULT_BOARD_SIZE;
+        for (int i = 0; i < totalMoves; i++) {
+            if (player == Board.P1)
+                board = mcts3.findNextMove(board, player);
+            else
+                board = mcts1.findNextMove(board, player);
+
+            if (board.checkStatus() != -1) {
+                break;
+            }
+            player = 3 - player;
+        }
+        int winStatus = board.checkStatus();
+        assertTrue(winStatus == Board.DRAW || winStatus == Board.P1);
+    }
+
+}

algorithms/src/test/java/algorithms/minimax/MinimaxTest.java

@@ -0,0 +1,36 @@
+package algorithms.minimax;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+import com.baeldung.algorithms.minimax.MiniMax;
+import com.baeldung.algorithms.minimax.Tree;
+
+public class MinimaxTest {
+    private Tree gameTree;
+    private MiniMax miniMax;
+
+    @Before
+    public void initMiniMaxUtility() {
+        miniMax = new MiniMax();
+    }
+
+    @Test
+    public void givenMiniMax_whenConstructTree_thenNotNullTree() {
+        assertNull(gameTree);
+        miniMax.constructTree(6);
+        gameTree = miniMax.getTree();
+        assertNotNull(gameTree);
+    }
+
+    @Test
+    public void givenMiniMax_whenCheckWin_thenComputeOptimal() {
+        miniMax.constructTree(6);
+        boolean result = miniMax.checkWin();
+        assertTrue(result);
+        miniMax.constructTree(8);
+        result = miniMax.checkWin();
+        assertFalse(result);
+    }
+}

asciidoctor/README.md

@@ -0,0 +1,3 @@
+### Relevant articles
+
+- [Introduction to Asciidoctor](http://www.baeldung.com/introduction-to-asciidoctor)

asciidoctor/pom.xml

@@ -0,0 +1,56 @@
+<?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">
+    <parent>
+        <artifactId>parent-modules</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>asciidoctor</artifactId>
+    <name>asciidoctor</name>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.asciidoctor</groupId>
+                <artifactId>asciidoctor-maven-plugin</artifactId>
+                <version>1.5.5</version>
+                <dependencies>
+                    <dependency>
+                        <groupId>org.asciidoctor</groupId>
+                        <artifactId>asciidoctorj-pdf</artifactId>
+                        <version>1.5.0-alpha.15</version>
+                    </dependency>
+                </dependencies>
+                <executions>
+                    <execution>
+                        <id>output-pdf</id>
+                        <phase>generate-resources</phase>
+                        <goals>
+                            <goal>process-asciidoc</goal>
+                        </goals>
+                    </execution>
+                </executions>
+                <configuration>
+                    <sourceDirectory>src/docs/asciidoc</sourceDirectory>
+                    <outputDirectory>target/docs/asciidoc</outputDirectory>
+                    <backend>pdf</backend>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <dependencies>        
+        <dependency>
+            <groupId>org.asciidoctor</groupId>
+            <artifactId>asciidoctorj</artifactId>
+            <version>1.5.4</version>
+        </dependency>
+        <dependency>
+            <groupId>org.asciidoctor</groupId>
+            <artifactId>asciidoctorj-pdf</artifactId>
+            <version>1.5.0-alpha.11</version>
+        </dependency>        
+    </dependencies>
+</project>

asciidoctor/src/docs/asciidoc/test.adoc

@@ -0,0 +1,3 @@
+== Introduction Section
+
+Hi. I'm a simple test to see if this Maven build is working. If you see me in a nice PDF, then it means everything is [red]#working#.

asciidoctor/src/main/java/com/baeldung/asciidoctor/AsciidoctorDemo.java

@@ -0,0 +1,33 @@
+package com.baeldung.asciidoctor;
+
+import static org.asciidoctor.Asciidoctor.Factory.create;
+import static org.asciidoctor.OptionsBuilder.options;
+
+import java.io.File;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.asciidoctor.Asciidoctor;
+
+public class AsciidoctorDemo {
+
+    private final Asciidoctor asciidoctor;
+
+    AsciidoctorDemo() {
+        asciidoctor = create();
+    }
+
+    public void generatePDFFromString(final String input) {
+
+        final Map<String, Object> options = options().inPlace(true)
+          .backend("pdf")
+          .asMap();
+
+
+        final String outfile = asciidoctor.convertFile(new File("sample.adoc"), options);
+    }
+
+    String generateHTMLFromString(final String input) {
+        return asciidoctor.convert("Hello _Baeldung_!", new HashMap<String, Object>());
+    }
+}

asciidoctor/src/test/java/com/baeldung/asciidoctor/AsciidoctorDemoTest.java

@@ -0,0 +1,13 @@
+package com.baeldung.asciidoctor;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class AsciidoctorDemoTest {
+
+    @Test
+    public void givenString_whenConverting_thenResultingHTMLCode() {
+        final AsciidoctorDemo asciidoctorDemo = new AsciidoctorDemo();
+        Assert.assertEquals(asciidoctorDemo.generateHTMLFromString("Hello _Baeldung_!"), "<div class=\"paragraph\">\n<p>Hello <em>Baeldung</em>!</p>\n</div>");
+    }
+}

camel-api/README.md

@@ -0,0 +1,15 @@
+Example for the Article on Camel API with SpringBoot
+
+to start up, run:
+	mvn spring-boot:run
+	
+them, do a POST http request to:
+	http://localhost:8080/camel/api/bean 
+
+with the HEADER: Content-Type: application/json, 
+
+and a BODY Payload like {"id": 1,"name": "World"}
+
+and we will get a return code of 201 and the response: Hello, World - if the transform() method from Application class is uncommented and the process() method is commented
+
+or return code of 201 and the response: {"id": 10,"name": "Hello, World"} - if the transform() method from Application class is commented and the process() method is uncommented 

camel-api/pom.xml

@@ -0,0 +1,80 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+
+	<modelVersion>4.0.0</modelVersion>
+
+	<groupId>com.example</groupId>
+	<artifactId>spring-boot-camel</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+
+	<name>Spring-Boot - Camel API</name>
+
+	<properties>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+		<maven-compiler-plugin.version>3.6.0</maven-compiler-plugin.version>
+		<maven-surefire-plugin.version>2.19.1</maven-surefire-plugin.version>
+		<camel.version>2.19.1</camel.version>
+	    <spring-boot-starter.version>1.5.4.RELEASE</spring-boot-starter.version>
+	</properties>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.apache.camel</groupId>
+			<artifactId>camel-servlet-starter</artifactId>
+			<version>${camel.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.camel</groupId>
+			<artifactId>camel-jackson-starter</artifactId>
+			<version>${camel.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.camel</groupId>
+			<artifactId>camel-swagger-java-starter</artifactId>
+			<version>${camel.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.camel</groupId>
+			<artifactId>camel-spring-boot-starter</artifactId>
+			<version>${camel.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-web</artifactId>
+			<version>${spring-boot-starter.version}</version>
+		</dependency>
+	</dependencies>
+	
+	<build>
+		<defaultGoal>spring-boot:run</defaultGoal>
+
+		<plugins>
+			<plugin>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<version>${maven-compiler-plugin.version}</version>
+				<configuration>
+					<source>1.8</source>
+					<target>1.8</target>
+				</configuration>
+			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-surefire-plugin</artifactId>
+				<version>${maven-surefire-plugin.version}</version>
+			</plugin>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+				<version>${spring-boot-starter.version}</version>
+				<executions>
+					<execution>
+						<goals>
+							<goal>repackage</goal>
+						</goals>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
+</project>

camel-api/src/main/java/com/baeldung/camel/Application.java

@@ -0,0 +1,104 @@
+package com.baeldung.camel;
+
+import javax.ws.rs.core.MediaType;
+
+import org.apache.camel.CamelContext;
+import org.apache.camel.Exchange;
+import org.apache.camel.Processor;
+import org.apache.camel.builder.RouteBuilder;
+import org.apache.camel.component.servlet.CamelHttpTransportServlet;
+import org.apache.camel.impl.DefaultCamelContext;
+import org.apache.camel.model.rest.RestBindingMode;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.web.servlet.ServletRegistrationBean;
+import org.springframework.boot.web.support.SpringBootServletInitializer;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.stereotype.Component;
+
+@SpringBootApplication
+@ComponentScan(basePackages="com.baeldung.camel")
+public class Application extends SpringBootServletInitializer {
+
+    @Value("${server.port}")
+    String serverPort;
+    
+    @Value("${baeldung.api.path}")
+    String contextPath;
+    
+    public static void main(String[] args) {
+        SpringApplication.run(Application.class, args);
+    }
+
+    @Bean
+    ServletRegistrationBean servletRegistrationBean() {
+        ServletRegistrationBean servlet = new ServletRegistrationBean(new CamelHttpTransportServlet(), contextPath+"/*");
+        servlet.setName("CamelServlet");
+        return servlet;
+    }
+
+
+    @Component
+    class RestApi extends RouteBuilder {
+
+        @Override
+        public void configure() {
+
+            CamelContext context = new DefaultCamelContext();
+
+            
+            // http://localhost:8080/camel/api-doc
+            restConfiguration().contextPath(contextPath) //
+                .port(serverPort)
+                .enableCORS(true)
+                .apiContextPath("/api-doc")
+                .apiProperty("api.title", "Test REST API")
+                .apiProperty("api.version", "v1")
+                .apiProperty("cors", "true") // cross-site
+                .apiContextRouteId("doc-api")
+                .component("servlet")
+                .bindingMode(RestBindingMode.json)
+                .dataFormatProperty("prettyPrint", "true");
+/** 
+The Rest DSL supports automatic binding json/xml contents to/from POJOs using Camels Data Format.
+By default the binding mode is off, meaning there is no automatic binding happening for incoming and outgoing messages.
+You may want to use binding if you develop POJOs that maps to your REST services request and response types. 
+This allows you, as a developer, to work with the POJOs in Java code.
+*/         
+            
+            rest("/api/").description("Teste REST Service")
+                .id("api-route")
+                .post("/bean")
+                .produces(MediaType.APPLICATION_JSON)
+                .consumes(MediaType.APPLICATION_JSON)
+//                .get("/hello/{place}")
+                .bindingMode(RestBindingMode.auto)
+                .type(MyBean.class)
+                .enableCORS(true)
+//                .outType(OutBean.class)
+
+                .to("direct:remoteService");
+            
+       
+            from("direct:remoteService")
+                .routeId("direct-route")
+                .tracing()
+                .log(">>> ${body.id}")
+                .log(">>> ${body.name}")
+//                .transform().simple("blue ${in.body.name}")                
+                .process(new Processor() {
+                    @Override
+                    public void process(Exchange exchange) throws Exception {
+                        MyBean bodyIn = (MyBean) exchange.getIn().getBody();
+                        
+                        ExampleServices.example(bodyIn);
+
+                        exchange.getIn().setBody(bodyIn);
+                    }
+                })
+                .setHeader(Exchange.HTTP_RESPONSE_CODE, constant(201));
+        }
+    }
+}

camel-api/src/main/java/com/baeldung/camel/ExampleServices.java

@@ -0,0 +1,15 @@
+package com.baeldung.camel;
+
+/**
+ * a Mock class to show how some other layer
+ * (a persistence layer, for instance)
+ * could be used insida a Camel
+ * 
+ */
+public class ExampleServices {
+
+    public static void example(MyBean bodyIn) {
+        bodyIn.setName( "Hello, " + bodyIn.getName() );
+        bodyIn.setId(bodyIn.getId()*10);
+    }
+}

camel-api/src/main/java/com/baeldung/camel/MyBean.java

@@ -0,0 +1,18 @@
+package com.baeldung.camel;
+
+public class MyBean {
+    private Integer id;
+    private String name;
+    public Integer getId() {
+        return id;
+    }
+    public void setId(Integer id) {
+        this.id = id;
+    }
+    public String getName() {
+        return name;
+    }
+    public void setName(String name) {
+        this.name = name;
+    }
+}

camel-api/src/main/resources/application.properties

@@ -0,0 +1,15 @@
+logging.config=classpath:logback.xml
+
+# the options from org.apache.camel.spring.boot.CamelConfigurationProperties can be configured here
+camel.springboot.name=MyCamel
+
+# lets listen on all ports to ensure we can be invoked from the pod IP
+server.address=0.0.0.0
+management.address=0.0.0.0
+
+# lets use a different management port in case you need to listen to HTTP requests on 8080
+management.port=8081
+
+# disable all management enpoints except health
+endpoints.enabled = true
+endpoints.health.enabled = true

camel-api/src/main/resources/application.yml

@@ -0,0 +1,27 @@
+server:
+  port: 8080
+
+# for example purposes of Camel version 2.18 and below
+baeldung:
+  api:
+    path: '/camel' 
+
+camel:
+  springboot:
+    # The Camel context name
+    name: ServicesRest
+
+# Binding health checks to a different port
+management:
+  port: 8081
+
+# disable all management enpoints except health
+endpoints:
+  enabled: false
+  health:
+    enabled: true
+
+# The application configuration properties
+quickstart:
+  generateOrderPeriod: 10s
+  processOrderPeriod: 30s

camel-api/src/main/resources/logback.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE xml>
+<configuration>
+
+  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+    <!-- encoders are assigned the type
+         ch.qos.logback.classic.encoder.PatternLayoutEncoder by default -->
+    <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>

core-java-9/pom.xml

@@ -47,6 +47,13 @@
             <version>${mockito.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>com.jayway.awaitility</groupId>
+            <artifactId>awaitility</artifactId>
+            <version>${awaitility.version}</version>
+            <scope>test</scope>
+        </dependency>
+
 
     </dependencies>
 
@@ -90,6 +97,7 @@
         <org.hamcrest.version>1.3</org.hamcrest.version>
         <junit.version>4.12</junit.version>
         <mockito.version>1.10.19</mockito.version>
+        <awaitility.version>1.7.0</awaitility.version>
     </properties>
 
 </project>

core-java-9/src/main/java/com/baeldung/java9/streams.reactive/EndSubscriber.java

@@ -0,0 +1,43 @@
+package com.baeldung.java9.streams.reactive;
+
+import java.util.LinkedList;
+import java.util.List;
+import java.util.concurrent.Flow.Subscriber;
+import java.util.concurrent.Flow.Subscription;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class EndSubscriber<T> implements Subscriber<T> {
+    private final AtomicInteger howMuchMessagesToConsume;
+    private Subscription subscription;
+    public List<T> consumedElements = new LinkedList<>();
+
+    public EndSubscriber(Integer howMuchMessagesToConsume) {
+        this.howMuchMessagesToConsume = new AtomicInteger(howMuchMessagesToConsume);
+    }
+
+    @Override
+    public void onSubscribe(Subscription subscription) {
+        this.subscription = subscription;
+        subscription.request(1);
+    }
+
+    @Override
+    public void onNext(T item) {
+        howMuchMessagesToConsume.decrementAndGet();
+        System.out.println("Got : " + item);
+        consumedElements.add(item);
+        if (howMuchMessagesToConsume.get() > 0) {
+            subscription.request(1);
+        }
+    }
+
+    @Override
+    public void onError(Throwable t) {
+        t.printStackTrace();
+    }
+
+    @Override
+    public void onComplete() {
+        System.out.println("Done");
+    }
+}

core-java-9/src/main/java/com/baeldung/java9/streams.reactive/TransformProcessor.java

@@ -0,0 +1,38 @@
+package com.baeldung.java9.streams.reactive;
+
+import java.util.concurrent.Flow;
+import java.util.concurrent.SubmissionPublisher;
+import java.util.function.Function;
+
+public class TransformProcessor<T, R> extends SubmissionPublisher<R> implements Flow.Processor<T, R> {
+
+    private Function<T, R> function;
+    private Flow.Subscription subscription;
+
+    public TransformProcessor(Function<T, R> function) {
+        super();
+        this.function = function;
+    }
+
+    @Override
+    public void onSubscribe(Flow.Subscription subscription) {
+        this.subscription = subscription;
+        subscription.request(1);
+    }
+
+    @Override
+    public void onNext(T item) {
+        submit(function.apply(item));
+        subscription.request(1);
+    }
+
+    @Override
+    public void onError(Throwable t) {
+        t.printStackTrace();
+    }
+
+    @Override
+    public void onComplete() {
+        close();
+    }
+}  

core-java-9/src/main/java/com/baeldung/java9/time/TimeApi.java

@@ -0,0 +1,43 @@
+package com.baeldung.java9.time;
+
+import java.time.LocalDate;
+import java.time.temporal.ChronoUnit;
+import java.util.ArrayList;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.GregorianCalendar;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+public class TimeApi {
+
+    public static List<Date> getDatesBetweenUsingJava7(Date startDate, Date endDate) {
+        List<Date> datesInRange = new ArrayList<Date>();
+        Calendar calendar = new GregorianCalendar();
+        calendar.setTime(startDate);
+
+        Calendar endCalendar = new GregorianCalendar();
+        endCalendar.setTime(endDate);
+
+        while (calendar.before(endCalendar)) {
+            Date result = calendar.getTime();
+            datesInRange.add(result);
+            calendar.add(Calendar.DATE, 1);
+        }
+        return datesInRange;
+    }
+
+    public static List<LocalDate> getDatesBetweenUsingJava8(LocalDate startDate, LocalDate endDate) {
+        long numOfDaysBetween = ChronoUnit.DAYS.between(startDate, endDate);
+        return IntStream.iterate(0, i -> i + 1)
+                 .limit(numOfDaysBetween)
+                 .mapToObj(i -> startDate.plusDays(i))
+                 .collect(Collectors.toList());
+    }
+
+    public static List<LocalDate> getDatesBetweenUsingJava9(LocalDate startDate, LocalDate endDate) {
+        return startDate.datesUntil(endDate).collect(Collectors.toList());
+    }
+
+}

core-java-9/src/test/java/com/baeldung/java9/streams.reactive/ReactiveStreamsTest.java

@@ -0,0 +1,73 @@
+package com.baeldung.java9.streams.reactive;
+
+
+import org.junit.Test;
+
+import java.util.List;
+import java.util.concurrent.SubmissionPublisher;
+
+import static org.assertj.core.api.Java6Assertions.assertThat;
+
+public class ReactiveStreamsTest {
+
+    @Test
+    public void givenPublisher_whenSubscribeToIt_thenShouldConsumeAllElements() throws InterruptedException {
+        //given
+        SubmissionPublisher<String> publisher = new SubmissionPublisher<>();
+        EndSubscriber<String> subscriber = new EndSubscriber<>(6);
+        publisher.subscribe(subscriber);
+        List<String> items = List.of("1", "x", "2", "x", "3", "x");
+
+        //when
+        assertThat(publisher.getNumberOfSubscribers()).isEqualTo(1);
+        items.forEach(publisher::submit);
+        publisher.close();
+
+        //then
+
+        await().atMost(1000, TimeUnit.MILLISECONDS).until(
+                () -> assertThat(subscriber.consumedElements).containsExactlyElementsOf(items)
+        );
+    }
+
+    @Test
+    public void givenPublisher_whenSubscribeAndTransformElements_thenShouldConsumeAllElements() throws InterruptedException {
+        //given
+        SubmissionPublisher<String> publisher = new SubmissionPublisher<>();
+        TransformProcessor<String, Integer> transformProcessor = new TransformProcessor<>(Integer::parseInt);
+        EndSubscriber<Integer> subscriber = new EndSubscriber<>(3);
+        List<String> items = List.of("1", "2", "3");
+        List<Integer> expectedResult = List.of(1, 2, 3);
+
+        //when
+        publisher.subscribe(transformProcessor);
+        transformProcessor.subscribe(subscriber);
+        items.forEach(publisher::submit);
+        publisher.close();
+
+        //then
+        await().atMost(1000, TimeUnit.MILLISECONDS).until(
+                () -> assertThat(subscriber.consumedElements).containsExactlyElementsOf(expectedResult)
+        );
+    }
+
+    @Test
+    public void givenPublisher_whenRequestForOnlyOneElement_thenShouldConsumeOnlyThatOne() throws InterruptedException {
+        //given
+        SubmissionPublisher<String> publisher = new SubmissionPublisher<>();
+        EndSubscriber<String> subscriber = new EndSubscriber<>(1);
+        publisher.subscribe(subscriber);
+        List<String> items = List.of("1", "x", "2", "x", "3", "x");
+        List<String> expected = List.of("1");
+
+        //when
+        assertThat(publisher.getNumberOfSubscribers()).isEqualTo(1);
+        items.forEach(publisher::submit);
+        publisher.close();
+
+        //then
+        await().atMost(1000, TimeUnit.MILLISECONDS).until(
+                () -> assertThat(subscriber.consumedElements).containsExactlyElementsOf(expected)
+        );
+    }
+}

core-java-9/src/test/java/com/baeldung/java9/time/TimeApiTest.java

@@ -0,0 +1,58 @@
+package com.baeldung.java9.time;
+
+import java.time.LocalDate;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import org.junit.Test;
+
+public class TimeApiTest {
+
+    @Test
+    public void givenGetDatesBetweenWithUsingJava7_WhenStartEndDate_thenDatesList() {
+        Date startDate = Calendar.getInstance().getTime();
+        Calendar endCalendar = Calendar.getInstance();
+        endCalendar.add(Calendar.DATE, 2);
+        Date endDate = endCalendar.getTime();
+
+        List<Date> dates = TimeApi.getDatesBetweenUsingJava7(startDate, endDate);
+        assertEquals(dates.size(), 2);
+
+        Calendar calendar = Calendar.getInstance();
+        Date date1 = calendar.getTime();
+        assertEquals(dates.get(0).getDay(), date1.getDay());
+        assertEquals(dates.get(0).getMonth(), date1.getMonth());
+        assertEquals(dates.get(0).getYear(), date1.getYear());
+
+        calendar.add(Calendar.DATE, 1);
+        Date date2 = calendar.getTime();
+        assertEquals(dates.get(1).getDay(), date2.getDay());
+        assertEquals(dates.get(1).getMonth(), date2.getMonth());
+        assertEquals(dates.get(1).getYear(), date2.getYear());
+    }
+
+    @Test
+    public void givenGetDatesBetweenWithUsingJava8_WhenStartEndDate_thenDatesList() {
+        LocalDate startDate = LocalDate.now();
+        LocalDate endDate = LocalDate.now().plusDays(2);
+
+        List<LocalDate> dates = TimeApi.getDatesBetweenUsingJava8(startDate, endDate);
+        assertEquals(dates.size(), 2);
+        assertEquals(dates.get(0), LocalDate.now());
+        assertEquals(dates.get(1), LocalDate.now().plusDays(1));
+    }
+
+    @Test
+    public void givenGetDatesBetweenWithUsingJava9_WhenStartEndDate_thenDatesList() {
+        LocalDate startDate = LocalDate.now();
+        LocalDate endDate = LocalDate.now().plusDays(2);
+
+        List<LocalDate> dates = TimeApi.getDatesBetweenUsingJava9(startDate, endDate);
+        assertEquals(dates.size(), 2);
+        assertEquals(dates.get(0), LocalDate.now());
+        assertEquals(dates.get(1), LocalDate.now().plusDays(1));
+    }
+
+}

core-java/.gitignore

@@ -17,9 +17,10 @@
 
 # Files generated by integration tests
 *.txt
+backup-pom.xml
 /bin/
 /temp
 
 #IntelliJ specific
-.idea
+.idea/
 *.iml

core-java/README.md

@@ -113,4 +113,21 @@
 - [Difference Between Wait and Sleep in Java](http://www.baeldung.com/java-wait-and-sleep)
 - [LongAdder and LongAccumulator in Java](http://www.baeldung.com/java-longadder-and-longaccumulator)
 - [Using Java MappedByteBuffer](http://www.baeldung.com/java-mapped-byte-buffer)
-
+- [Dynamic Proxies in Java](http://www.baeldung.com/java-dynamic-proxies)
+- [How to Copy an Array in Java](http://www.baeldung.com/java-array-copy)
+- [Introduction to JDBC](http://www.baeldung.com/java-jdbc)
+- [Guide to CopyOnWriteArrayList](http://www.baeldung.com/java-copy-on-write-arraylist)
+- [Period and Duration in Java](http://www.baeldung.com/java-period-duration)
+- [Converting a Stack Trace to a String in Java](http://www.baeldung.com/java-stacktrace-to-string)
+- [Guide to the Java Phaser](http://www.baeldung.com/java-phaser)
+- [Count Occurrences of a Char in a String](http://www.baeldung.com/java-count-chars)
+- [Java Double Brace Initialization](http://www.baeldung.com/java-double-brace-initialization)
+- [The StackOverflowError in Java](http://www.baeldung.com/java-stack-overflow-error)
+- [Split a String in Java](http://www.baeldung.com/java-split-string)
+- [Introduction to Java Serialization](http://www.baeldung.com/java-serialization)
+- [How to Remove the Last Character of a String?](http://www.baeldung.com/java-remove-last-character-of-string)
+- [Guide to Synchronized Keyword in Java](http://www.baeldung.com/java-synchronized)
+- [ClassNotFoundException vs NoClassDefFoundError](http://www.baeldung.com/java-classnotfoundexception-and-noclassdeffounderror)
+- [Guide to UUID in Java](http://www.baeldung.com/java-uuid)
+- [How to Get the Last Element of a Stream in Java?](http://www.baeldung.com/java-stream-last-element)
+- [Guide to Escaping Characters in Java RegExps](http://www.baeldung.com/java-regexp-escape-char)

core-java/pom.xml

@@ -177,6 +177,11 @@
             <version>2.1.0.1</version>
         </dependency>
 
+        <dependency>
+            <groupId>com.sun.messaging.mq</groupId>
+            <artifactId>fscontext</artifactId>
+            <version>${fscontext.version}</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -322,6 +327,22 @@
                 </executions>
             </plugin>
 
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>1.6.0</version>
+                <configuration>
+                    <executable>java</executable>
+                    <mainClass>com.baeldung.outofmemoryerror.OutOfMemoryGCLimitExceed</mainClass>
+                    <arguments>
+                        <argument>-Xmx300m</argument>
+                        <argument>-XX:+UseParallelGC</argument>
+                        <argument>-classpath</argument>
+                        <classpath/>
+                        <argument>com.baeldung.outofmemoryerror.OutOfMemoryGCLimitExceed</argument>
+                    </arguments>
+                </configuration>
+            </plugin>
         </plugins>
 
     </build>
@@ -382,6 +403,7 @@
         <unix4j.version>0.4</unix4j.version>
         <grep4j.version>1.8.7</grep4j.version>
         <lombok.version>1.16.12</lombok.version>
+        <fscontext.version>4.6-b01</fscontext.version>
 
         <!-- testing -->
         <org.hamcrest.version>1.3</org.hamcrest.version>
@@ -395,5 +417,4 @@
         <maven-surefire-plugin.version>2.19.1</maven-surefire-plugin.version>
 
     </properties>
-
 </project>

core-java/src/main/java/com/baeldung/concurrent/blockingqueue/NumbersConsumer.java

@@ -6,7 +6,7 @@ public class NumbersConsumer implements Runnable {
     private final BlockingQueue<Integer> queue;
     private final int poisonPill;
 
-    public NumbersConsumer(BlockingQueue<Integer> queue, int poisonPill) {
+    NumbersConsumer(BlockingQueue<Integer> queue, int poisonPill) {
         this.queue = queue;
         this.poisonPill = poisonPill;
     }

core-java/src/main/java/com/baeldung/concurrent/blockingqueue/NumbersProducer.java

@@ -9,7 +9,7 @@ public class NumbersProducer implements Runnable {
     private final int poisonPill;
     private final int poisonPillPerProducer;
 
-    public NumbersProducer(BlockingQueue<Integer> numbersQueue, int poisonPill, int poisonPillPerProducer) {
+    NumbersProducer(BlockingQueue<Integer> numbersQueue, int poisonPill, int poisonPillPerProducer) {
         this.numbersQueue = numbersQueue;
         this.poisonPill = poisonPill;
         this.poisonPillPerProducer = poisonPillPerProducer;

core-java/src/main/java/com/baeldung/concurrent/countdownlatch/BrokenWorker.java

@@ -7,7 +7,7 @@ public class BrokenWorker implements Runnable {
     private final List<String> outputScraper;
     private final CountDownLatch countDownLatch;
 
-    public BrokenWorker(final List<String> outputScraper, final CountDownLatch countDownLatch) {
+    BrokenWorker(final List<String> outputScraper, final CountDownLatch countDownLatch) {
         this.outputScraper = outputScraper;
         this.countDownLatch = countDownLatch;
     }

core-java/src/main/java/com/baeldung/concurrent/countdownlatch/WaitingWorker.java

@@ -10,7 +10,7 @@ public class WaitingWorker implements Runnable {
     private final CountDownLatch callingThreadBlocker;
     private final CountDownLatch completedThreadCounter;
 
-    public WaitingWorker(final List<String> outputScraper, final CountDownLatch readyThreadCounter, final CountDownLatch callingThreadBlocker, CountDownLatch completedThreadCounter) {
+    WaitingWorker(final List<String> outputScraper, final CountDownLatch readyThreadCounter, final CountDownLatch callingThreadBlocker, CountDownLatch completedThreadCounter) {
 
         this.outputScraper = outputScraper;
         this.readyThreadCounter = readyThreadCounter;

core-java/src/main/java/com/baeldung/concurrent/countdownlatch/Worker.java

@@ -7,7 +7,7 @@ public class Worker implements Runnable {
     private final List<String> outputScraper;
     private final CountDownLatch countDownLatch;
 
-    public Worker(final List<String> outputScraper, final CountDownLatch countDownLatch) {
+    Worker(final List<String> outputScraper, final CountDownLatch countDownLatch) {
         this.outputScraper = outputScraper;
         this.countDownLatch = countDownLatch;
     }

core-java/src/main/java/com/baeldung/concurrent/cyclicbarrier/CyclicBarrierDemo.java

@@ -0,0 +1,81 @@
+package com.baeldung.concurrent.cyclicbarrier;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Random;
+import java.util.concurrent.BrokenBarrierException;
+import java.util.concurrent.CyclicBarrier;
+
+public class CyclicBarrierDemo {
+
+    private CyclicBarrier cyclicBarrier;
+    private List<List<Integer>> partialResults = Collections.synchronizedList(new ArrayList<>());
+    private Random random = new Random();
+    private int NUM_PARTIAL_RESULTS;
+    private int NUM_WORKERS;
+
+
+    private void runSimulation(int numWorkers, int numberOfPartialResults) {
+        NUM_PARTIAL_RESULTS = numberOfPartialResults;
+        NUM_WORKERS = numWorkers;
+
+        cyclicBarrier = new CyclicBarrier(NUM_WORKERS, new AggregatorThread());
+        System.out.println("Spawning " + NUM_WORKERS + " worker threads to compute "
+                + NUM_PARTIAL_RESULTS + " partial results each");
+        for (int i = 0; i < NUM_WORKERS; i++) {
+            Thread worker = new Thread(new NumberCruncherThread());
+            worker.setName("Thread " + i);
+            worker.start();
+        }
+    }
+
+    class NumberCruncherThread implements Runnable {
+
+        @Override
+        public void run() {
+            String thisThreadName = Thread.currentThread().getName();
+            List<Integer> partialResult = new ArrayList<>();
+            for (int i = 0; i < NUM_PARTIAL_RESULTS; i++) {
+                Integer num = random.nextInt(10);
+                System.out.println(thisThreadName
+                        + ": Crunching some numbers! Final result - " + num);
+                partialResult.add(num);
+            }
+            partialResults.add(partialResult);
+            try {
+                System.out.println(thisThreadName + " waiting for others to reach barrier.");
+                cyclicBarrier.await();
+            } catch (InterruptedException | BrokenBarrierException e) {
+                e.printStackTrace();
+            }
+        }
+    }
+
+    class AggregatorThread implements Runnable {
+
+        @Override
+        public void run() {
+            String thisThreadName = Thread.currentThread().getName();
+            System.out.println(thisThreadName + ": Computing final sum of " + NUM_WORKERS
+                    + " workers, having " + NUM_PARTIAL_RESULTS + " results each.");
+            int sum = 0;
+            for (List<Integer> threadResult : partialResults) {
+                System.out.print("Adding ");
+                for (Integer partialResult : threadResult) {
+                    System.out.print(partialResult+" ");
+                    sum += partialResult;
+                }
+                System.out.println();
+            }
+            System.out.println(Thread.currentThread().getName() + ": Final result = " + sum);
+        }
+
+    }
+
+    public static void main(String[] args) {
+        CyclicBarrierDemo play = new CyclicBarrierDemo();
+        play.runSimulation(5, 3);
+    }
+
+}

core-java/src/main/java/com/baeldung/concurrent/delayqueue/DelayObject.java

@@ -9,7 +9,7 @@ public class DelayObject implements Delayed {
     private String data;
     private long startTime;
 
-    public DelayObject(String data, long delayInMilliseconds) {
+    DelayObject(String data, long delayInMilliseconds) {
         this.data = data;
         this.startTime = System.currentTimeMillis() + delayInMilliseconds;
     }

core-java/src/main/java/com/baeldung/concurrent/delayqueue/DelayQueueConsumer.java

@@ -7,9 +7,9 @@ import java.util.concurrent.atomic.AtomicInteger;
 public class DelayQueueConsumer implements Runnable {
     private BlockingQueue<DelayObject> queue;
     private final Integer numberOfElementsToTake;
-    public final AtomicInteger numberOfConsumedElements = new AtomicInteger();
+    final AtomicInteger numberOfConsumedElements = new AtomicInteger();
 
-    public DelayQueueConsumer(BlockingQueue<DelayObject> queue, Integer numberOfElementsToTake) {
+    DelayQueueConsumer(BlockingQueue<DelayObject> queue, Integer numberOfElementsToTake) {
         this.queue = queue;
         this.numberOfElementsToTake = numberOfElementsToTake;
     }

core-java/src/main/java/com/baeldung/concurrent/delayqueue/DelayQueueProducer.java

@@ -9,7 +9,7 @@ public class DelayQueueProducer implements Runnable {
     private final Integer numberOfElementsToProduce;
     private final Integer delayOfEachProducedMessageMilliseconds;
 
-    public DelayQueueProducer(BlockingQueue<DelayObject> queue,
+    DelayQueueProducer(BlockingQueue<DelayObject> queue,
                        Integer numberOfElementsToProduce,
                        Integer delayOfEachProducedMessageMilliseconds) {
         this.queue = queue;

core-java/src/main/java/com/baeldung/concurrent/diningphilosophers/Philosopher.java

@@ -5,7 +5,7 @@ public class Philosopher implements Runnable {
     private final Object leftFork;
     private final Object rightFork;
 
-    public Philosopher(Object left, Object right) {
+    Philosopher(Object left, Object right) {
         this.leftFork = left;
         this.rightFork = right;
     }
@@ -30,7 +30,6 @@ public class Philosopher implements Runnable {
             }
         } catch (InterruptedException e) {
             Thread.currentThread().interrupt();
-            return;
         }
     }
 }

core-java/src/main/java/com/baeldung/concurrent/future/FactorialSquareCalculator.java

@@ -7,7 +7,7 @@ public class FactorialSquareCalculator extends RecursiveTask<Integer> {
 
     final private Integer n;
 
-    public FactorialSquareCalculator(Integer n) {
+    FactorialSquareCalculator(Integer n) {
         this.n = n;
     }
 

core-java/src/main/java/com/baeldung/concurrent/future/SquareCalculator.java

@@ -3,15 +3,15 @@ package com.baeldung.concurrent.future;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Future;
 
-public class SquareCalculator {
+class SquareCalculator {
 
     private final ExecutorService executor;
 
-    public SquareCalculator(ExecutorService executor) {
+    SquareCalculator(ExecutorService executor) {
         this.executor = executor;
     }
 
-    public Future<Integer> calculate(Integer input) {
+    Future<Integer> calculate(Integer input) {
         return executor.submit(() -> {
             Thread.sleep(1000);
             return input * input;

core-java/src/main/java/com/baeldung/concurrent/locks/ReentrantLockWithCondition.java

@@ -13,23 +13,23 @@ import static java.lang.Thread.sleep;
 
 public class ReentrantLockWithCondition {
 
-	static Logger logger = LoggerFactory.getLogger(ReentrantLockWithCondition.class);
+    private static Logger LOG = LoggerFactory.getLogger(ReentrantLockWithCondition.class);
 
-	Stack<String> stack = new Stack<>();
+    private Stack<String> stack = new Stack<>();
-	int CAPACITY = 5;
+    private static final int CAPACITY = 5;
 
-	ReentrantLock lock = new ReentrantLock();
+    private ReentrantLock lock = new ReentrantLock();
-	Condition stackEmptyCondition = lock.newCondition();
+    private Condition stackEmptyCondition = lock.newCondition();
-	Condition stackFullCondition = lock.newCondition();
+    private Condition stackFullCondition = lock.newCondition();
 
-	public void pushToStack(String item) throws InterruptedException {
+    private void pushToStack(String item) throws InterruptedException {
         try {
             lock.lock();
             if (stack.size() == CAPACITY) {
-				logger.info(Thread.currentThread().getName() + " wait on stack full");
+                LOG.info(Thread.currentThread().getName() + " wait on stack full");
                 stackFullCondition.await();
             }
-			logger.info("Pushing the item " + item);
+            LOG.info("Pushing the item " + item);
             stack.push(item);
             stackEmptyCondition.signalAll();
         } finally {
@@ -38,11 +38,11 @@ public class ReentrantLockWithCondition {
 
     }
 
-	public String popFromStack() throws InterruptedException {
+    private String popFromStack() throws InterruptedException {
         try {
             lock.lock();
             if (stack.size() == 0) {
-				logger.info(Thread.currentThread().getName() + " wait on stack empty");
+                LOG.info(Thread.currentThread().getName() + " wait on stack empty");
                 stackEmptyCondition.await();
             }
             return stack.pop();
@@ -70,7 +70,7 @@ public class ReentrantLockWithCondition {
         service.execute(() -> {
             for (int i = 0; i < 10; i++) {
                 try {
-					logger.info("Item popped " + object.popFromStack());
+                    LOG.info("Item popped " + object.popFromStack());
                 } catch (InterruptedException e) {
                     e.printStackTrace();
                 }

core-java/src/main/java/com/baeldung/concurrent/locks/SharedObjectWithLock.java

@@ -12,48 +12,48 @@ import static java.lang.Thread.sleep;
 
 public class SharedObjectWithLock {
 
-	Logger logger = LoggerFactory.getLogger(SharedObjectWithLock.class);
+    private static final Logger LOG = LoggerFactory.getLogger(SharedObjectWithLock.class);
 
-	ReentrantLock lock = new ReentrantLock(true);
+    private ReentrantLock lock = new ReentrantLock(true);
 
-	int counter = 0;
+    private int counter = 0;
 
-	public void perform() {
+    void perform() {
 
         lock.lock();
-		logger.info("Thread - " + Thread.currentThread().getName() + " acquired the lock");
+        LOG.info("Thread - " + Thread.currentThread().getName() + " acquired the lock");
         try {
-			logger.info("Thread - " + Thread.currentThread().getName() + " processing");
+            LOG.info("Thread - " + Thread.currentThread().getName() + " processing");
             counter++;
         } catch (Exception exception) {
-			logger.error(" Interrupted Exception ", exception);
+            LOG.error(" Interrupted Exception ", exception);
         } finally {
             lock.unlock();
-			logger.info("Thread - " + Thread.currentThread().getName() + " released the lock");
+            LOG.info("Thread - " + Thread.currentThread().getName() + " released the lock");
         }
     }
 
-	public void performTryLock() {
+    private void performTryLock() {
 
-		logger.info("Thread - " + Thread.currentThread().getName() + " attempting to acquire the lock");
+        LOG.info("Thread - " + Thread.currentThread().getName() + " attempting to acquire the lock");
         try {
             boolean isLockAcquired = lock.tryLock(2, TimeUnit.SECONDS);
             if (isLockAcquired) {
                 try {
-					logger.info("Thread - " + Thread.currentThread().getName() + " acquired the lock");
+                    LOG.info("Thread - " + Thread.currentThread().getName() + " acquired the lock");
 
-					logger.info("Thread - " + Thread.currentThread().getName() + " processing");
+                    LOG.info("Thread - " + Thread.currentThread().getName() + " processing");
                     sleep(1000);
                 } finally {
                     lock.unlock();
-					logger.info("Thread - " + Thread.currentThread().getName() + " released the lock");
+                    LOG.info("Thread - " + Thread.currentThread().getName() + " released the lock");
 
                 }
             }
         } catch (InterruptedException exception) {
-			logger.error(" Interrupted Exception ", exception);
+            LOG.error(" Interrupted Exception ", exception);
         }
-		logger.info("Thread - " + Thread.currentThread().getName() + " could not acquire the lock");
+        LOG.info("Thread - " + Thread.currentThread().getName() + " could not acquire the lock");
     }
 
     public ReentrantLock getLock() {
@@ -78,12 +78,8 @@ public class SharedObjectWithLock {
         final ExecutorService service = Executors.newFixedThreadPool(threadCount);
         final SharedObjectWithLock object = new SharedObjectWithLock();
 
-		service.execute(() -> {
+        service.execute(object::perform);
-			object.perform();
+        service.execute(object::performTryLock);
-		});
-		service.execute(() -> {
-			object.performTryLock();
-		});
 
         service.shutdown();
 

core-java/src/main/java/com/baeldung/concurrent/locks/StampedLockDemo.java

@@ -12,8 +12,8 @@ import java.util.concurrent.locks.StampedLock;
 import static java.lang.Thread.sleep;
 
 public class StampedLockDemo {
-	Map<String, String> map = new HashMap<>();
+    private Map<String, String> map = new HashMap<>();
-	Logger logger = LoggerFactory.getLogger(StampedLockDemo.class);
+    private Logger logger = LoggerFactory.getLogger(StampedLockDemo.class);
 
     private final StampedLock lock = new StampedLock();
 
@@ -44,7 +44,7 @@ public class StampedLockDemo {
 
     }
 
-	public String readWithOptimisticLock(String key) throws InterruptedException {
+    private String readWithOptimisticLock(String key) throws InterruptedException {
         long stamp = lock.tryOptimisticRead();
         String value = map.get(key);
 

core-java/src/main/java/com/baeldung/concurrent/locks/SynchronizedHashMapWithRWLock.java

@@ -15,8 +15,8 @@ import static java.lang.Thread.sleep;
 
 public class SynchronizedHashMapWithRWLock {
 
-	static Map<String, String> syncHashMap = new HashMap<>();
+    private static Map<String, String> syncHashMap = new HashMap<>();
-	Logger logger = LoggerFactory.getLogger(SynchronizedHashMapWithRWLock.class);
+    private Logger logger = LoggerFactory.getLogger(SynchronizedHashMapWithRWLock.class);
 
     private final ReadWriteLock lock = new ReentrantReadWriteLock();
     private final Lock readLock = lock.readLock();
@@ -84,7 +84,7 @@ public class SynchronizedHashMapWithRWLock {
 
         SynchronizedHashMapWithRWLock object;
 
-		public Reader(SynchronizedHashMapWithRWLock object) {
+        Reader(SynchronizedHashMapWithRWLock object) {
             this.object = object;
         }
 

core-java/src/main/java/com/baeldung/concurrent/semaphores/CounterUsingMutex.java

@@ -0,0 +1,31 @@
+package com.baeldung.concurrent.semaphores;
+
+import java.util.concurrent.Semaphore;
+
+class CounterUsingMutex {
+
+    private final Semaphore mutex;
+    private int count;
+
+    CounterUsingMutex() {
+        mutex = new Semaphore(1);
+        count = 0;
+    }
+
+    void increase() throws InterruptedException {
+        mutex.acquire();
+        this.count = this.count + 1;
+        Thread.sleep(1000);
+        mutex.release();
+
+    }
+
+    int getCount() {
+        return this.count;
+    }
+
+    boolean hasQueuedThreads() {
+        return mutex.hasQueuedThreads();
+    }
+
+}

core-java/src/main/java/com/baeldung/concurrent/semaphores/DelayQueueUsingTimedSemaphore.java

@@ -0,0 +1,23 @@
+package com.baeldung.concurrent.semaphores;
+
+import java.util.concurrent.TimeUnit;
+
+import org.apache.commons.lang3.concurrent.TimedSemaphore;
+
+class DelayQueueUsingTimedSemaphore {
+
+    private final TimedSemaphore semaphore;
+
+    DelayQueueUsingTimedSemaphore(long period, int slotLimit) {
+        semaphore = new TimedSemaphore(period, TimeUnit.SECONDS, slotLimit);
+    }
+
+    boolean tryAdd() {
+        return semaphore.tryAcquire();
+    }
+
+    int availableSlots() {
+        return semaphore.getAvailablePermits();
+    }
+
+}

core-java/src/main/java/com/baeldung/concurrent/semaphores/LoginQueueUsingSemaphore.java

@@ -0,0 +1,25 @@
+package com.baeldung.concurrent.semaphores;
+
+import java.util.concurrent.Semaphore;
+
+class LoginQueueUsingSemaphore {
+
+    private final Semaphore semaphore;
+
+    LoginQueueUsingSemaphore(int slotLimit) {
+        semaphore = new Semaphore(slotLimit);
+    }
+
+    boolean tryLogin() {
+        return semaphore.tryAcquire();
+    }
+
+    void logout() {
+        semaphore.release();
+    }
+
+    int availableSlots() {
+        return semaphore.availablePermits();
+    }
+
+}

core-java/src/main/java/com/baeldung/concurrent/skiplist/Event.java

@@ -2,20 +2,20 @@ package com.baeldung.concurrent.skiplist;
 
 import java.time.ZonedDateTime;
 
-public class Event {
+class Event {
     private final ZonedDateTime eventTime;
     private final String content;
 
-    public Event(ZonedDateTime eventTime, String content) {
+    Event(ZonedDateTime eventTime, String content) {
         this.eventTime = eventTime;
         this.content = content;
     }
 
-    public ZonedDateTime getEventTime() {
+    ZonedDateTime getEventTime() {
         return eventTime;
     }
 
-    public String getContent() {
+    String getContent() {
         return content;
     }
 }

core-java/src/main/java/com/baeldung/concurrent/skiplist/EventWindowSort.java

@@ -5,21 +5,21 @@ import java.util.Comparator;
 import java.util.concurrent.ConcurrentNavigableMap;
 import java.util.concurrent.ConcurrentSkipListMap;
 
-public class EventWindowSort {
+class EventWindowSort {
     private final ConcurrentSkipListMap<ZonedDateTime, String> events
       = new ConcurrentSkipListMap<>(Comparator.comparingLong(value -> value.toInstant().toEpochMilli()));
 
-    public void acceptEvent(Event event) {
+    void acceptEvent(Event event) {
         events.put(event.getEventTime(), event.getContent());
     }
 
-    public ConcurrentNavigableMap<ZonedDateTime, String> getEventsFromLastMinute() {
+    ConcurrentNavigableMap<ZonedDateTime, String> getEventsFromLastMinute() {
         return events.tailMap(ZonedDateTime
           .now()
           .minusMinutes(1));
     }
 
-    public ConcurrentNavigableMap<ZonedDateTime, String> getEventsOlderThatOneMinute() {
+    ConcurrentNavigableMap<ZonedDateTime, String> getEventsOlderThatOneMinute() {
         return events.headMap(ZonedDateTime
           .now()
           .minusMinutes(1));

core-java/src/main/java/com/baeldung/concurrent/sleepwait/WaitSleepExample.java

@@ -13,10 +13,10 @@ public class WaitSleepExample {
     private static final Object LOCK = new Object();
 
     public static void main(String... args) throws InterruptedException {
-        sleepWaitInSyncronizedBlocks();
+        sleepWaitInSynchronizedBlocks();
     }
 
-    private static void sleepWaitInSyncronizedBlocks() throws InterruptedException {
+    private static void sleepWaitInSynchronizedBlocks() throws InterruptedException {
         Thread.sleep(1000); // called on the thread
         LOG.debug("Thread '" + Thread.currentThread().getName() + "' is woken after sleeping for 1 second");
 

core-java/src/main/java/com/baeldung/concurrent/synchronize/BaeldungSynchronizedBlocks.java

@@ -5,13 +5,13 @@ public class BaeldungSynchronizedBlocks {
     private int count = 0;
     private static int staticCount = 0;
 
-    public void performSynchronisedTask() {
+    void performSynchronisedTask() {
         synchronized (this) {
             setCount(getCount() + 1);
         }
     }
 
-    public static void performStaticSyncTask() {
+    static void performStaticSyncTask() {
         synchronized (BaeldungSynchronizedBlocks.class) {
             setStaticCount(getStaticCount() + 1);
         }
@@ -25,11 +25,11 @@ public class BaeldungSynchronizedBlocks {
         this.count = count;
     }
 
-    public static int getStaticCount() {
+    static int getStaticCount() {
         return staticCount;
     }
 
-    public static void setStaticCount(int staticCount) {
+    private static void setStaticCount(int staticCount) {
         BaeldungSynchronizedBlocks.staticCount = staticCount;
     }
 }

core-java/src/main/java/com/baeldung/concurrent/synchronize/BaeldungSynchronizedMethods.java

@@ -5,17 +5,17 @@ public class BaeldungSynchronizedMethods {
     private int sum = 0;
     private int syncSum = 0;
 
-    public static int staticSum = 0;
+    static int staticSum = 0;
 
-    public void calculate() {
+    void calculate() {
         setSum(getSum() + 1);
     }
 
-    public synchronized void synchronisedCalculate() {
+    synchronized void synchronisedCalculate() {
         setSyncSum(getSyncSum() + 1);
     }
 
-    public static synchronized void syncStaticCalculate() {
+    static synchronized void syncStaticCalculate() {
         staticSum = staticSum + 1;
     }
 
@@ -27,11 +27,11 @@ public class BaeldungSynchronizedMethods {
         this.sum = sum;
     }
 
-    public int getSyncSum() {
+    int getSyncSum() {
         return syncSum;
     }
 
-    public void setSyncSum(int syncSum) {
+    private void setSyncSum(int syncSum) {
         this.syncSum = syncSum;
     }
 }

core-java/src/main/java/com/baeldung/datetime/UseLocalDate.java

@@ -6,40 +6,40 @@ import java.time.LocalDateTime;
 import java.time.temporal.ChronoUnit;
 import java.time.temporal.TemporalAdjusters;
 
-public class UseLocalDate {
+class UseLocalDate {
 
-    public LocalDate getLocalDateUsingFactoryOfMethod(int year, int month, int dayOfMonth) {
+    LocalDate getLocalDateUsingFactoryOfMethod(int year, int month, int dayOfMonth) {
         return LocalDate.of(year, month, dayOfMonth);
     }
 
-    public LocalDate getLocalDateUsingParseMethod(String representation) {
+    LocalDate getLocalDateUsingParseMethod(String representation) {
         return LocalDate.parse(representation);
     }
 
-    public LocalDate getLocalDateFromClock() {
+    LocalDate getLocalDateFromClock() {
         LocalDate localDate = LocalDate.now();
         return localDate;
     }
 
-    public LocalDate getNextDay(LocalDate localDate) {
+    LocalDate getNextDay(LocalDate localDate) {
         return localDate.plusDays(1);
     }
 
-    public LocalDate getPreviousDay(LocalDate localDate) {
+    LocalDate getPreviousDay(LocalDate localDate) {
         return localDate.minus(1, ChronoUnit.DAYS);
     }
 
-    public DayOfWeek getDayOfWeek(LocalDate localDate) {
+    DayOfWeek getDayOfWeek(LocalDate localDate) {
         DayOfWeek day = localDate.getDayOfWeek();
         return day;
     }
 
-    public LocalDate getFirstDayOfMonth() {
+    LocalDate getFirstDayOfMonth() {
         LocalDate firstDayOfMonth = LocalDate.now().with(TemporalAdjusters.firstDayOfMonth());
         return firstDayOfMonth;
     }
 
-    public LocalDateTime getStartOfDay(LocalDate localDate) {
+    LocalDateTime getStartOfDay(LocalDate localDate) {
         LocalDateTime startofDay = localDate.atStartOfDay();
         return startofDay;
     }

core-java/src/main/java/com/baeldung/datetime/UseLocalTime.java

@@ -5,31 +5,27 @@ import java.time.temporal.ChronoUnit;
 
 public class UseLocalTime {
 
-    public LocalTime getLocalTimeUsingFactoryOfMethod(int hour, int min, int seconds) {
+    LocalTime getLocalTimeUsingFactoryOfMethod(int hour, int min, int seconds) {
-        LocalTime localTime = LocalTime.of(hour, min, seconds);
+        return LocalTime.of(hour, min, seconds);
-        return localTime;
     }
 
-    public LocalTime getLocalTimeUsingParseMethod(String timeRepresentation) {
+    LocalTime getLocalTimeUsingParseMethod(String timeRepresentation) {
-        LocalTime localTime = LocalTime.parse(timeRepresentation);
+        return LocalTime.parse(timeRepresentation);
-        return localTime;
     }
 
-    public LocalTime getLocalTimeFromClock() {
+    private LocalTime getLocalTimeFromClock() {
-        LocalTime localTime = LocalTime.now();
+        return LocalTime.now();
-        return localTime;
     }
 
-    public LocalTime addAnHour(LocalTime localTime) {
+    LocalTime addAnHour(LocalTime localTime) {
-        LocalTime newTime = localTime.plus(1, ChronoUnit.HOURS);
+        return localTime.plus(1, ChronoUnit.HOURS);
-        return newTime;
     }
 
-    public int getHourFromLocalTime(LocalTime localTime) {
+    int getHourFromLocalTime(LocalTime localTime) {
         return localTime.getHour();
     }
 
-    public LocalTime getLocalTimeWithMinuteSetToValue(LocalTime localTime, int minute) {
+    LocalTime getLocalTimeWithMinuteSetToValue(LocalTime localTime, int minute) {
         return localTime.withMinute(minute);
     }
 }

core-java/src/main/java/com/baeldung/datetime/UsePeriod.java

@@ -3,13 +3,13 @@ package com.baeldung.datetime;
 import java.time.LocalDate;
 import java.time.Period;
 
-public class UsePeriod {
+class UsePeriod {
 
-    public LocalDate modifyDates(LocalDate localDate, Period period) {
+    LocalDate modifyDates(LocalDate localDate, Period period) {
         return localDate.plus(period);
     }
 
-    public Period getDifferenceBetweenDates(LocalDate localDate1, LocalDate localDate2) {
+    Period getDifferenceBetweenDates(LocalDate localDate1, LocalDate localDate2) {
         return Period.between(localDate1, localDate2);
     }
 }

core-java/src/main/java/com/baeldung/datetime/UseToInstant.java

@@ -8,12 +8,10 @@ import java.util.Date;
 public class UseToInstant {
 
     public LocalDateTime convertDateToLocalDate(Date date) {
-        LocalDateTime localDateTime = LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault());
+        return LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault());
-        return localDateTime;
     }
 
     public LocalDateTime convertDateToLocalDate(Calendar calendar) {
-        LocalDateTime localDateTime = LocalDateTime.ofInstant(calendar.toInstant(), ZoneId.systemDefault());
+        return LocalDateTime.ofInstant(calendar.toInstant(), ZoneId.systemDefault());
-        return localDateTime;
     }
 }

core-java/src/main/java/com/baeldung/datetime/UseZonedDateTime.java

@@ -4,10 +4,9 @@ import java.time.LocalDateTime;
 import java.time.ZoneId;
 import java.time.ZonedDateTime;
 
-public class UseZonedDateTime {
+class UseZonedDateTime {
 
-    public ZonedDateTime getZonedDateTime(LocalDateTime localDateTime, ZoneId zoneId) {
+    ZonedDateTime getZonedDateTime(LocalDateTime localDateTime, ZoneId zoneId) {
-        ZonedDateTime zonedDateTime = ZonedDateTime.of(localDateTime, zoneId);
+        return ZonedDateTime.of(localDateTime, zoneId);
-        return zonedDateTime;
     }
 }

core-java/src/main/java/com/baeldung/deserialization/AppleProduct.java

@@ -0,0 +1,26 @@
+package com.baeldung.deserialization;
+
+import java.io.Serializable;
+
+public class AppleProduct implements Serializable {
+
+     private static final long serialVersionUID = 1234567L; // user-defined (i.e. not default or generated)
+//    private static final long serialVersionUID = 7654321L; // user-defined (i.e. not default or generated)
+
+    public String headphonePort;
+    public String thunderboltPort;
+    public String lighteningPort;
+
+    public String getHeadphonePort() {
+        return headphonePort;
+    }
+
+    public String getThunderboltPort() {
+        return thunderboltPort;
+    }
+
+    public static long getSerialVersionUID() {
+        return serialVersionUID;
+    }
+
+}

core-java/src/main/java/com/baeldung/deserialization/DeserializationUtility.java

@@ -0,0 +1,27 @@
+package com.baeldung.deserialization;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.util.Base64;
+
+public class DeserializationUtility {
+
+    public static void main(String[] args) throws ClassNotFoundException, IOException {
+
+        String serializedObj = "rO0ABXNyACljb20uYmFlbGR1bmcuZGVzZXJpYWxpemF0aW9uLkFwcGxlUHJvZHVjdAAAAAAAEtaHAgADTAANaGVhZHBob25lUG9ydHQAEkxqYXZhL2xhbmcvU3RyaW5nO0wADmxpZ2h0ZW5pbmdQb3J0cQB+AAFMAA90aHVuZGVyYm9sdFBvcnRxAH4AAXhwdAARaGVhZHBob25lUG9ydDIwMjBwdAATdGh1bmRlcmJvbHRQb3J0MjAyMA==";
+        System.out.println("Deserializing AppleProduct...");
+        AppleProduct deserializedObj = (AppleProduct) deSerializeObjectFromString(serializedObj);
+        System.out.println("Headphone port of AppleProduct:" + deserializedObj.getHeadphonePort());
+        System.out.println("Thunderbolt port of AppleProduct:" + deserializedObj.getThunderboltPort());
+    }
+
+    public static Object deSerializeObjectFromString(String s) throws IOException, ClassNotFoundException {
+        byte[] data = Base64.getDecoder().decode(s);
+        ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(data));
+        Object o = ois.readObject();
+        ois.close();
+        return o;
+    }
+
+}

core-java/src/main/java/com/baeldung/deserialization/SerializationUtility.java

@@ -0,0 +1,30 @@
+package com.baeldung.deserialization;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
+import java.util.Base64;
+
+public class SerializationUtility {
+
+    public static void main(String[] args) throws ClassNotFoundException, IOException {
+
+        AppleProduct macBook = new AppleProduct();
+        macBook.headphonePort = "headphonePort2020";
+        macBook.thunderboltPort = "thunderboltPort2020";
+
+        String serializedObj = serializeObjectToString(macBook);
+        System.out.println("Serialized AppleProduct object to string:");
+        System.out.println(serializedObj);
+    }
+
+    public static String serializeObjectToString(Serializable o) throws IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        ObjectOutputStream oos = new ObjectOutputStream(baos);
+        oos.writeObject(o);
+        oos.close();
+        return Base64.getEncoder().encodeToString(baos.toByteArray());
+    }
+
+}

core-java/src/main/java/com/baeldung/dirmonitoring/DirectoryMonitoringExample.java

@@ -13,8 +13,7 @@ public class DirectoryMonitoringExample {
 
     private static final Logger LOG = LoggerFactory.getLogger(DirectoryMonitoringExample.class);
 
-
+    private static final int POLL_INTERVAL = 500;
-    public static final int POLL_INTERVAL = 500;
 
     public static void main(String[] args) throws Exception {
         FileAlterationObserver observer = new FileAlterationObserver(System.getProperty("user.home"));

core-java/src/main/java/com/baeldung/doublecolon/Computer.java

@@ -6,12 +6,12 @@ public class Computer {
     private String color;
     private Integer healty;
 
-    public Computer(final int age, final String color) {
+    Computer(final int age, final String color) {
         this.age = age;
         this.color = color;
     }
 
-    public Computer(final Integer age, final String color, final Integer healty) {
+    Computer(final Integer age, final String color, final Integer healty) {
         this.age = age;
         this.color = color;
         this.healty = healty;
@@ -28,7 +28,7 @@ public class Computer {
         this.age = age;
     }
 
-    public String getColor() {
+    String getColor() {
         return color;
     }
 
@@ -36,11 +36,11 @@ public class Computer {
         this.color = color;
     }
 
-    public Integer getHealty() {
+    Integer getHealty() {
         return healty;
     }
 
-    public void setHealty(final Integer healty) {
+    void setHealty(final Integer healty) {
         this.healty = healty;
     }
 
@@ -72,10 +72,7 @@ public class Computer {
 
         final Computer computer = (Computer) o;
 
-        if (age != null ? !age.equals(computer.age) : computer.age != null) {
+        return (age != null ? age.equals(computer.age) : computer.age == null) && (color != null ? color.equals(computer.color) : computer.color == null);
-            return false;
-        }
-        return color != null ? color.equals(computer.color) : computer.color == null;
 
     }
 

core-java/src/main/java/com/baeldung/doublecolon/ComputerUtils.java

@@ -7,8 +7,8 @@ import java.util.List;
 
 public class ComputerUtils {
 
-    public static final ComputerPredicate after2010Predicate = (c) -> (c.getAge() > 2010);
+    static final ComputerPredicate after2010Predicate = (c) -> (c.getAge() > 2010);
-    public static final ComputerPredicate blackPredicate = (c) -> "black".equals(c.getColor());
+    static final ComputerPredicate blackPredicate = (c) -> "black".equals(c.getColor());
 
     public static List<Computer> filter(final List<Computer> inventory, final ComputerPredicate p) {
 
@@ -18,7 +18,7 @@ public class ComputerUtils {
         return result;
     }
 
-    public static void repair(final Computer computer) {
+    static void repair(final Computer computer) {
         if (computer.getHealty() < 50) {
             computer.setHealty(100);
         }

core-java/src/main/java/com/baeldung/doublecolon/MacbookPro.java

@@ -13,7 +13,7 @@ public class MacbookPro extends Computer {
         super(age, color);
     }
 
-    public MacbookPro(Integer age, String color, Integer healty) {
+    MacbookPro(Integer age, String color, Integer healty) {
         super(age, color, healty);
     }
 

core-java/src/main/java/com/baeldung/dynamicproxy/TimingDynamicInvocationHandler.java

@@ -15,7 +15,7 @@ public class TimingDynamicInvocationHandler implements InvocationHandler {
 
     private Object target;
 
-    public TimingDynamicInvocationHandler(Object target) {
+    TimingDynamicInvocationHandler(Object target) {
         this.target = target;
 
         for(Method method: target.getClass().getDeclaredMethods()) {

core-java/src/main/java/com/baeldung/equalshashcode/entities/Square.java

@@ -1,10 +1,10 @@
 package com.baeldung.equalshashcode.entities;
 
-import java.awt.Color;
+import java.awt.*;
 
 public class Square extends Rectangle {
 
-    Color color;
+    private Color color;
 
     public Square(double width, Color color) {
         super(width, width);

core-java/src/main/java/com/baeldung/filesystem/jndi/LookupFSJNDI.java

@@ -0,0 +1,43 @@
+package com.baeldung.filesystem.jndi;
+
+import java.io.File;
+import java.util.Hashtable;
+
+import javax.naming.Context;
+import javax.naming.InitialContext;
+import javax.naming.NamingException;
+
+public class LookupFSJNDI {
+    private InitialContext ctx = null;
+
+    public LookupFSJNDI() throws NamingException {
+        super();
+        init();
+    }
+    
+    private void init() throws NamingException {
+        Hashtable<String, String> env = new Hashtable<String, String>();
+        
+        env.put (Context.INITIAL_CONTEXT_FACTORY,
+          "com.sun.jndi.fscontext.RefFSContextFactory");
+        // URI to namespace (actual directory)
+        env.put(Context.PROVIDER_URL, "file:./src/test/resources");
+        
+        ctx = new InitialContext(env);
+    }
+
+    public InitialContext getCtx() {
+        return ctx;
+    }
+    
+    public File getFile(String fileName) {
+        File file;
+        try {
+            file = (File)getCtx().lookup(fileName);
+        } catch (NamingException e) {
+            file = null;
+        }
+        return file;
+    }
+
+}

core-java/src/main/java/com/baeldung/java/reflection/DynamicGreeter.java

@@ -0,0 +1,23 @@
+package com.baeldung.java.reflection;
+
+import java.lang.annotation.Annotation;
+
+public class DynamicGreeter implements Greeter {
+    
+    private String greet;
+
+    public DynamicGreeter(String greet) {
+        this.greet = greet;
+    }
+
+    @Override
+    public Class<? extends Annotation> annotationType() {
+        return DynamicGreeter.class;
+    }
+
+    @Override
+    public String greet() {
+        return greet;
+    }
+
+}

core-java/src/main/java/com/baeldung/java/reflection/Greeter.java

@@ -0,0 +1,10 @@
+package com.baeldung.java.reflection;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Greeter {
+    
+    public String greet() default ""; 
+}

core-java/src/main/java/com/baeldung/java/reflection/GreetingAnnotation.java

@@ -0,0 +1,58 @@
+package com.baeldung.java.reflection;
+
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.util.Map;
+
+public class GreetingAnnotation {
+   
+    private static final String ANNOTATION_METHOD = "annotationData";
+    private static final String ANNOTATION_FIELDS = "declaredAnnotations";
+    private static final String ANNOTATIONS = "annotations";
+
+    public static void main(String ...args) {
+        Greeter greetings = Greetings.class.getAnnotation(Greeter.class);
+        System.err.println("Hello there, " + greetings.greet() + " !!");
+
+        Greeter targetValue = new DynamicGreeter("Good evening");
+        //alterAnnotationValueJDK8(Greetings.class, Greeter.class, targetValue);
+        alterAnnotationValueJDK7(Greetings.class, Greeter.class, targetValue);
+        
+        greetings = Greetings.class.getAnnotation(Greeter.class);
+        System.err.println("Hello there, " + greetings.greet() + " !!");
+    }
+    
+    @SuppressWarnings("unchecked")
+    public static void alterAnnotationValueJDK8(Class<?> targetClass, Class<? extends Annotation> targetAnnotation, Annotation targetValue) {
+        try {
+            Method method = Class.class.getDeclaredMethod(ANNOTATION_METHOD, null);
+            method.setAccessible(true);
+
+            Object annotationData = method.invoke(targetClass);
+            
+            Field annotations = annotationData.getClass().getDeclaredField(ANNOTATIONS);
+            annotations.setAccessible(true);
+
+            Map<Class<? extends Annotation>, Annotation> map = (Map<Class<? extends Annotation>, Annotation>) annotations.get(annotationData);
+            map.put(targetAnnotation, targetValue);
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+    
+    @SuppressWarnings("unchecked")
+    public static void alterAnnotationValueJDK7(Class<?> targetClass, Class<? extends Annotation> targetAnnotation, Annotation targetValue) {
+        try {            
+            Field annotations = Class.class.getDeclaredField(ANNOTATIONS);
+            annotations.setAccessible(true);
+
+            Map<Class<? extends Annotation>, Annotation> map = (Map<Class<? extends Annotation>, Annotation>) annotations.get(targetClass);
+            System.out.println(map);
+            map.put(targetAnnotation, targetValue);
+            System.out.println(map);
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+}

core-java/src/main/java/com/baeldung/java/reflection/Greetings.java

@@ -0,0 +1,6 @@
+package com.baeldung.java.reflection;
+
+@Greeter(greet="Good morning")
+public class Greetings {
+
+}

core-java/src/main/java/com/baeldung/javanetworking/url/URLDemo.java

@@ -0,0 +1,69 @@
+package com.baeldung.javanetworking.url;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.net.URLConnection;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class URLDemo {
+    private final Logger log = LoggerFactory.getLogger(URLDemo.class);
+
+    String URLSTRING = "https://wordpress.org:443/support/topic/page-jumps-within-wordpress/?replies=3#post-2278484";
+    // parsed locator
+    String URLPROTOCOL = "https";
+    // final static String URLAUTHORITY = "wordpress.org:443";
+    String URLHOST = "wordpress.org";
+    String URLPATH = "/support/topic/page-jumps-within-wordpress/";
+    // final static String URLFILENAME = "/support/topic/page-jumps-within-wordpress/?replies=3";
+    // final static int URLPORT = 443;
+    int URLDEFAULTPORT = 443;
+    String URLQUERY = "replies=3";
+    String URLREFERENCE = "post-2278484";
+    String URLCOMPOUND = URLPROTOCOL + "://" + URLHOST + ":" + URLDEFAULTPORT + URLPATH + "?" + URLQUERY + "#" + URLREFERENCE;
+
+    URL url;
+    URLConnection urlConnection = null;
+    HttpURLConnection connection = null;
+    BufferedReader in = null;
+    String urlContent = "";
+
+    public String testURL(String urlString) throws IOException, IllegalArgumentException {
+        String urlStringCont = "";
+        // comment the if clause if experiment with URL
+        /*if (!URLSTRING.equals(urlString)) {
+            throw new IllegalArgumentException("URL String argument is not proper: " + urlString);
+        }*/
+        // creating URL object
+        url = new URL(urlString);
+        // get URL connection
+        urlConnection = url.openConnection();
+        connection = null;
+        // we can check, if connection is proper type
+        if (urlConnection instanceof HttpURLConnection) {
+            connection = (HttpURLConnection) urlConnection;
+        } else {
+            log.info("Please enter an HTTP URL");
+            throw new IOException("HTTP URL is not correct");
+        }
+        // we can check response code (200 OK is expected)
+        log.info(connection.getResponseCode() + " " + connection.getResponseMessage());
+        in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
+        String current;
+
+        while ((current = in.readLine()) != null) {
+            urlStringCont += current;
+        }
+        return urlStringCont;
+    }
+
+    public static void main(String[] args) throws Exception {
+        URLDemo demo = new URLDemo();
+        String content = demo.testURL(demo.URLCOMPOUND);
+        demo.log.info(content);
+    }
+}

core-java/src/main/java/com/baeldung/map/iteration/MapIteration.java

@@ -0,0 +1,71 @@
+package com.baeldung.map.iteration;
+
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+
+public class MapIteration {
+
+    public static void main(String[] args) {
+        MapIteration mapIteration = new MapIteration();
+        Map<String, Integer> map = new HashMap<>();
+
+        map.put("One", 1);
+        map.put("Three", 3);
+        map.put("Two", 2);
+
+        System.out.println("Iterating Keys of Map Using KeySet");
+        mapIteration.iterateKeys(map);
+
+        System.out.println("Iterating Map Using Entry Set");
+        mapIteration.iterateUsingEntrySet(map);
+
+        System.out.println("Iterating Using Iterator and Map Entry");
+        mapIteration.iterateUsingIteratorAndEntry(map);
+
+        System.out.println("Iterating Using KeySet and For Each");
+        mapIteration.iterateUsingKeySetAndForeach(map);
+
+        System.out.println("Iterating Map Using Lambda Expression");
+        mapIteration.iterateUsingLambda(map);
+
+        System.out.println("Iterating Using Stream API");
+        mapIteration.iterateUsingStreamAPI(map);
+    }
+
+    public void iterateUsingEntrySet(Map<String, Integer> map) {
+        for (Map.Entry<String, Integer> entry : map.entrySet()) {
+            System.out.println(entry.getKey() + ":" + entry.getValue());
+        }
+    }
+
+    public void iterateUsingLambda(Map<String, Integer> map) {
+        map.forEach((k, v) -> System.out.println((k + ":" + v)));
+    }
+
+    public void iterateUsingIteratorAndEntry(Map<String, Integer> map) {
+        Iterator<Map.Entry<String, Integer>> iterator = map.entrySet().iterator();
+        while (iterator.hasNext()) {
+            Map.Entry<String, Integer> pair = iterator.next();
+            System.out.println(pair.getKey() + ":" + pair.getValue());
+        }
+    }
+
+    public void iterateUsingKeySetAndForeach(Map<String, Integer> map) {
+        for (String key : map.keySet()) {
+            System.out.println(key + ":" + map.get(key));
+        }
+    }
+
+    public void iterateUsingStreamAPI(Map<String, Integer> map) {
+        map.entrySet().stream().forEach(e -> System.out.println(e.getKey() + ":" + e.getValue()));
+    }
+
+    public void iterateKeys(Map<String, Integer> map) {
+        for (String key : map.keySet()) {
+            System.out.println(key);
+        }
+
+    }
+
+}

core-java/src/main/java/com/baeldung/maths/BigDecimalImpl.java

@@ -0,0 +1,18 @@
+package com.baeldung.maths;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
+public class BigDecimalImpl {
+
+    public static void main(String[] args) {
+
+        BigDecimal serviceTax = new BigDecimal("56.0084578639");
+        serviceTax = serviceTax.setScale(2, RoundingMode.CEILING);
+
+        BigDecimal entertainmentTax = new BigDecimal("23.00689");
+        entertainmentTax = entertainmentTax.setScale(2, RoundingMode.FLOOR);
+
+        BigDecimal totalTax = serviceTax.add(entertainmentTax);
+    }
+}

core-java/src/main/java/com/baeldung/maths/BigIntegerImpl.java

@@ -0,0 +1,16 @@
+package com.baeldung.maths;
+
+import java.math.BigInteger;
+
+public class BigIntegerImpl {
+
+    public static void main(String[] args) {
+
+        BigInteger numStarsMilkyWay = new BigInteger("8731409320171337804361260816606476");
+        BigInteger numStarsAndromeda = new BigInteger("5379309320171337804361260816606476");
+        
+        BigInteger totalStars = numStarsMilkyWay.add(numStarsAndromeda);
+
+    }
+
+}