TicTacToe.java

public class TicTacToe {
	//∗∗ Simulation of a Tic-Tac-Toe game (does not do strategy). ∗/
	
	public static final int X = 1;
	public static final int O = -1;
	public static final int EMPTY = 0;
	private int board[ ][ ] = new int[3][3]; 
	private int player;
	//∗∗ Constructor ∗/
	public TicTacToe( ) { clearBoard( ); } //∗∗ Clears the board ∗/
	
	public void clearBoard( ) {
		for (int i = 0; i < 3; i++) for (int j = 0; j < 3; j++)
			board[i][j] = EMPTY; player = X;
			// players
			// empty cell
			// game board // current player
			// every cell should be empty // the first player is 'X'
	}
	
	//∗∗ Puts an X or O mark at position i,j. ∗/
	public void putMark(int i, int j) throws IllegalArgumentException {
		if ((i<0)||(i>2)||(j<0)||(j>2))
			throw new IllegalArgumentException("Invalid board position");
		if (board[i][j] != EMPTY)
			throw new IllegalArgumentException("Board position occupied");
		board[i][j] = player; // place the mark for the current player
		player = -player; // switch players (uses fact that O = - X) }
	}
	
	//∗∗ Checks whether the board configuration is a win for the given player. ∗/
	public boolean isWin(int mark) {
		return ((board[0][0] + board[0][1] + board[0][2] == mark*3)
				||(board[1][0]+board[1][1]+board[1][2] == mark*3)
				||(board[2][0]+board[2][1]+board[2][2] == mark*3)
				||(board[0][0]+board[1][0]+board[2][0] == mark*3)
				||(board[0][1]+board[1][1]+board[2][1] == mark*3)
				||(board[0][2]+board[1][2]+board[2][2] == mark*3)
				||(board[0][0]+board[1][1]+board[2][2] == mark*3)
				||(board[2][0]+board[1][1]+board[0][2] == mark*3));
				}
	//row0 
	//row1 
	//row2
	// column 0 
	// column 1 
    // column 2 
    // diagonal 
	// rev diag
	
	//return winner
	public int winner(){
		if(isWin(X)){
			return(X);
		}
		else if(isWin(O)){
			return(O);
		}
		else
			return 0;
	}
	
	//return show on the board
	public String toString(){
		StringBuilder sb = new StringBuilder();
		for(int i=0;i<3;i++){
			for(int j=0;j<3;j++){
				switch (board[i][j]){
				case X: sb.append("X");break;
				case O: sb.append("O");break;
				case EMPTY: sb.append(" ");break;
				}
				if(j<2)sb.append("|");	//column boundary
			}
			if(i<2)sb.append("\n-----\n");  //row boundary
			
		}
		return sb.toString();
	}
	
	//main
	public static void main(String[] args){
		TicTacToe game = new TicTacToe();
		//X move       			//O move
		game.putMark(1,1); 		game.putMark(0,2);
		
		
		
		System.out.println(game);
		int winningplayer =game.winner();
		String[] outcome= {"O wins","Tie","X wins"};
		System.out.println(outcome[1+winningplayer]);
	}
	
}