Merge branch 'master' into master

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

@@ -5,7 +5,6 @@ import java.util.List;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Stack;
-import java.util.stream.Collectors;
 
 public class HillClimbing {
     public static void main(String[] args) {
@@ -22,7 +21,7 @@ public class HillClimbing {
         }
     }
 
-    public static void printEachStep(State state) {
+    private static void printEachStep(State state) {
         List<Stack<String>> stackList = state.getState();
         System.out.println("----------------");
         stackList.forEach(stack -> {
@@ -33,8 +32,8 @@ public class HillClimbing {
         });
     }
 
-    public Stack<String> getStackWithValues(String[] blocks) {
-        Stack<String> stack = new Stack<String>();
+    private Stack<String> getStackWithValues(String[] blocks) {
+        Stack<String> stack = new Stack<>();
         for (String block : blocks)
             stack.push(block);
         return stack;
@@ -42,14 +41,9 @@ public class HillClimbing {
 
     /**
      * This method prepares path from init state to goal state
-     *
-     * @param initStateStack
-     * @param goalStateStack
-     * @return
-     * @throws Exception
      */
     public List<State> getRouteWithHillClimbing(Stack<String> initStateStack, Stack<String> goalStateStack) throws Exception {
-        List<Stack<String>> initStateStackList = new ArrayList<Stack<String>>();
+        List<Stack<String>> initStateStackList = new ArrayList<>();
         initStateStackList.add(initStateStack);
         int initStateHeuristics = getHeuristicsValue(initStateStackList, goalStateStack);
         State initState = new State(initStateStackList, initStateHeuristics);
@@ -71,57 +65,51 @@ public class HillClimbing {
             }
         }
 
-        if (noStateFound)
-            throw new Exception("No path found");
         return resultPath;
     }
 
     /**
      * This method finds new state from current state based on goal and
      * heuristics
-     *
-     * @param currentState
-     * @param goalStateStack
-     * @return a next state
      */
     public State findNextState(State currentState, Stack<String> goalStateStack) {
         List<Stack<String>> listOfStacks = currentState.getState();
         int currentStateHeuristics = currentState.getHeuristics();
 
-        Optional<State> newState = listOfStacks.stream()
+        return listOfStacks.stream()
             .map(stack -> {
-                State tempState = null;
-                List<Stack<String>> tempStackList = new ArrayList<Stack<String>>(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;
+                return applyOperationsOnState(listOfStacks, stack, currentStateHeuristics, goalStateStack);
             })
             .filter(Objects::nonNull)
-            .findFirst();
-
-        return newState.orElse(null);
+            .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
-     *
-     * @param currentStackList
-     * @param block
-     * @param currentStateHeuristics
-     * @param goalStateStack
-     * @return a new state
      */
     private State pushElementToNewStack(List<Stack<String>> currentStackList, String block, int currentStateHeuristics, Stack<String> goalStateStack) {
         State newState = null;
-        Stack<String> newStack = new Stack<String>();
+        Stack<String> newStack = new Stack<>();
         newStack.push(block);
 
         currentStackList.add(newStack);
@@ -138,62 +126,64 @@ public class HillClimbing {
      * 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
-     *
-     * @param stack
-     * @param currentStackList
-     * @param block
-     * @param currentStateHeuristics
-     * @param goalStateStack
-     * @return a new state
      */
     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 -> {
-                stack.push(block);
-                int newStateHeuristics = getHeuristicsValue(currentStackList, goalStateStack);
-                if (newStateHeuristics > currentStateHeuristics) {
-                    return new State(currentStackList, newStateHeuristics);
-                }
-                stack.pop();
-                return null;
+                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
-     *
-     * @param currentState
-     * @param goalStateStack
-     * @return
      */
     public int getHeuristicsValue(List<Stack<String>> currentState, Stack<String> goalStateStack) {
-
-        Integer heuristicValue = 0;
+        Integer heuristicValue;
         heuristicValue = currentState.stream()
             .mapToInt(stack -> {
-                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;
+                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

@@ -5,26 +5,23 @@ import java.util.List;
 import java.util.Stack;
 
 public class State {
-    List<Stack<String>> state;
-    int heuristics;
-
-    public State() {
-    }
+    private List<Stack<String>> state;
+    private int heuristics;
 
     public State(List<Stack<String>> state) {
         this.state = state;
     }
 
-    public State(List<Stack<String>> state, int heuristics) {
+    State(List<Stack<String>> state, int heuristics) {
         this.state = state;
         this.heuristics = heuristics;
     }
 
-    public State(State state) {
+    State(State state) {
         if (state != null) {
-            this.state = new ArrayList<Stack<String>>();
+            this.state = new ArrayList<>();
             for (Stack s : state.getState()) {
-                Stack s1 = new Stack();
+                Stack s1;
                 s1 = (Stack) s.clone();
                 this.state.add(s1);
             }
@@ -36,10 +33,6 @@ public class State {
         return state;
     }
 
-    public void setState(List<Stack<String>> state) {
-        this.state = state;
-    }
-
     public int getHeuristics() {
         return 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/test/java/algorithms/HillClimbingAlgorithmTest.java

@@ -14,17 +14,17 @@ import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 
 public class HillClimbingAlgorithmTest {
-    Stack<String> initStack;
-    Stack<String> goalStack;
+    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<String>();
+        initStack = new Stack<>();
         for (String block : blockArr)
             initStack.push(block);
-        goalStack = new Stack<String>();
+        goalStack = new Stack<>();
         for (String block : goalBlockArr)
             goalStack.push(block);
     }
@@ -48,7 +48,7 @@ public class HillClimbingAlgorithmTest {
     @Test
     public void givenCurrentState_whenFindNextState_thenBetterHeuristics() {
         HillClimbing hillClimbing = new HillClimbing();
-        List<Stack<String>> initList = new ArrayList<Stack<String>>();
+        List<Stack<String>> initList = new ArrayList<>();
         initList.add(initStack);
         State currentState = new State(initList);
         currentState.setHeuristics(hillClimbing.getHeuristicsValue(initList, goalStack));

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);
+    }
+
+}

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>");
+    }
+}

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

@@ -0,0 +1,86 @@
+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;
+
+/**
+ * Created by cv on 24/6/17.
+ */
+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;
+
+
+    public 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 e) {
+                e.printStackTrace();
+            } catch (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);
+    }
+
+}