TicTacToy engine

Board.java

package model;

public class Board {

    private final Piece[][] cells;

    public Board(int width, int height) {
        cells = new Piece[width][height];
    }

    public Piece getPiece(int x, int y) {
        return cells[x][y];
    }

    public void setPiece(Piece piece, int x, int y) {
        cells[x][y] = piece;
    }

    public boolean isCellEmpty(int x, int y) {
        return getPiece(x, y) == null;
    }
}

Game.java

package model;

import constant.Type;
import constant.WinState;

public class Game {

    private static final int BOARD_WIDTH = 3;

    private static final int BOARD_HEIGHT = 3;

    private final Board board;

    private final Player player1;

    private final Player player2;

    private Player activePlayer;

    public Game() {
        board = new Board(BOARD_WIDTH, BOARD_HEIGHT);
        player1 = new Player(Type.X);
        player2 = new Player(Type.O);
        activePlayer = player1;
    }

    public void forfeit() {
        if (activePlayer == player1) {
            player1.setWinState(WinState.LOSER);
            player2.setWinState(WinState.WINNER);
        } else {
            player2.setWinState(WinState.LOSER);
            player1.setWinState(WinState.WINNER);
        }
    }

    public void setPlayer1Name(String name) {
        player1.setName(name);
    }

    public void setPlayer2Name(String name) {
        player2.setName(name);
    }

    public void play(int x, int y) {
        if (board.isCellEmpty(x, y)) {
            Piece piece = activePlayer.getPiece();
            board.setPiece(piece, x, y);
        }

        for (int iX = 0; iX < BOARD_WIDTH; iX++) {
            for (int iY = 0; iY < BOARD_HEIGHT; iY++) {
                // TODO iterate over the board and see if activePlayer has won
            }
        }

        activePlayer = activePlayer == player1 ? player2 : player1;
    }
}

Piece.java

package model;

public class Piece {

    private final char type;

    public Piece(char type) {
        this.type = type;
    }

    public char getType() {
        return type;
    }
}

Player.java

package model;

public class Player {

    private final char type;

    private String name;

    private int winState;

    public Player(char type) {
        this.type = type;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Piece getPiece() {
        return new Piece(type);
    }

    public int getWinState() {
        return winState;
    }

    public void setWinState(int winState) {
        this.winState = winState;
    }
}

Type.java

package constant;

public class Type {
    public static final char X = 'x';
    public static final char O = 'O';
}

WinState.java

package constant;

public class WinState {
    public static final int PLAYING = 0;
    public static final int WINNER = 1;
    public static final int LOSER = 2;
    public static final int DRAW = 3;
}