Connect4Board.java

// Connect 4 board and utilities

public class Connect4Board {
  public final int height;
  public final int width;
  private int[][] board;
  private boolean nextTurn;
   // board contents
  public static final int EMPTY_SLOT = 0;
  public static final int PLAYER_1_DISK = 1;
  public static final int PLAYER_2_DISK = 2;

  // turns
  public static final boolean PLAYER_1_TURN = true;
  public static final boolean PLAYER_2_TURN = false;

  // game state
  public static final int ONGOING = 0;
  public static final int PLAYER_1_WON = 1;
  public static final int PLAYER_2_WON = 2;
  public static final int TIE = 3;

  public Connect4Board(int width, int height) {
    this.width = width;
    this.height = height;
    board = new int[height][width]; // default all 0
    nextTurn = PLAYER_1_TURN;
  }

  public Connect4Board() {
    this(7, 6);
  }

  public Connect4Board(int[][] contents, boolean nextTurn) {
    this(contents[0].length, contents.length);
    loadContents(contents);
    this.nextTurn = nextTurn;
  }

  public boolean canPlace(int column) {
    return column >= 0 && column < width && board[0][column] == 0;
  }

  public boolean place(int column) {
    int disk = (nextTurn == PLAYER_1_TURN) ? PLAYER_1_DISK : PLAYER_2_DISK;
    if(!canPlace(column))
      return false;
    int diskHeight = height - 1;
    while(board[diskHeight][column] != EMPTY_SLOT)
      diskHeight--;
    board[diskHeight][column] = disk;
    nextTurn = !nextTurn;
    return true;
  }

  public Connect4Board getNextState(int column) {
    Connect4Board next = this.copy();
    next.place(column);
    return next;
  }

  public int[][] getContents() {
    int[][] contentsCopy = new int[height][width];
    for(int i = 0; i < height; i++)
      for(int j = 0; j < width; j++)
        contentsCopy[i][j] = board[i][j];
    return contentsCopy;
  }

  public void loadContents(int[][] contents) {
    for(int i = 0; i < height; i++)
      for(int j = 0; j < width; j++)
        board[i][j] = contents[i][j];
  }

  public Connect4Board copy() {
    return new Connect4Board(board, this.nextTurn);
  }

  public boolean didPlayerWin(int playerDisk) {
    // check horizontal
    int height = board.length;
    int width = board[0].length;
    for(int i = 0; i < height; i++)
      for(int j = 0; j < width - 3; j++)
        for(int k = j; k < j + 4 && board[i][k] == playerDisk; k++)
          if(k == j+3)
            return true;
    // check vertical
    for(int i = 0; i < height - 3; i++)
      for(int j = 0; j < width; j++)
        for(int k = i; k < i + 4 && board[k][j] == playerDisk; k++)
          if(k == i+3)
            return true;
    // check diagonal down right
    for(int i = 0; i < height - 3; i++)
      for(int j = 0; j < width - 3; j++)
        for(int k = 0; k < 4 && board[i+k][j+k] == playerDisk; k++)
          if(k == 3)
            return true;
    // check diagonal down
    for(int i = 0; i < height - 3; i++)
      for(int j = 3; j < width; j++)
        for(int k = 0; k < 4 && board[i+k][j-k] == playerDisk; k++)
          if(k == 3)
            return true;
    return false;
  }

  public boolean isFull() {
    for(int i = 0; i < board.length; i++)
      for(int j = 0; j < board[i].length; j++)
        if(board[i][j] == EMPTY_SLOT)
          return false;
    return true;
  }

   public int currentGameState() {
    return this.didPlayerWin(PLAYER_1_DISK) ? PLAYER_1_WON
      : this.didPlayerWin(PLAYER_2_DISK) ? PLAYER_2_WON
      : this.isFull() ? TIE
      : ONGOING;
  }

  public boolean getNextTurn() {
    return nextTurn;
  }

  @Override
  public String toString() {
    String result = "|-";
    for(int j = 0; j < width; j++) {
      result += "--|-";
    }
    result = result.substring(0, result.length()-1) + "\n";
    for(int i = 0; i < height; i++) {
      result += "| ";
      for(int j = 0; j < width; j++) {
        result += (board[i][j] == EMPTY_SLOT ? " " : (board[i][j] == 1 ? "\u2B55" : "\u274E"))+" | ";
      }
      result = result.substring(0, result.length()-1);
      result += "\n|-";
      for(int j = 0; j < width; j++) {
        result += "--|-";
      }
      result = result.substring(0, result.length()-1);
      result += "\n";
    }
    result+="  0   1   2   3   4   5   6  ";
    return result.substring(0, result.length()-1);
  }
}