toto.java

public class TicTacToe {

    public static boolean valid(String[] plays) {
        int xCount = 0;
        int oCount = 0;
        for (String p : plays) {
            if (!"x".equals(p) && !"o".equals(p) && !"".equals(p)) {
                return false;
            }
            if ("x".equals(p))
                xCount++;
            if ("o".equals(p))
                oCount++;
        }
        if (plays.length != 9)
            return false;
        if (xCount > oCount + 1 || xCount < oCount - 1)
            return false;
        return true;
    }

    public static int[][] winningPositions = new int[][] { { 0, 1, 2 }, { 3, 4, 5 }, { 6, 7, 8 },
            { 0, 3, 6 }, { 1, 4, 7 }, { 2, 5, 8 },
            { 0, 4, 8 }, { 2, 4, 6 } };

    public static boolean playerWins(String player, String[] plays) {
        for (int[] valid : winningPositions) {
            if (player.equals(plays[valid[0]]) && player.equals(plays[valid[1]]) && player.equals(plays[valid[2]]))
                return true;
        }
        return false;
    }

    public static String winner(String game) {
        game = game.toLowerCase();
        String[] plays = game.split(",", -1);
        if (!valid(plays)) {
            return "Error";
        }

        boolean xWin = playerWins("x", plays);
        boolean oWin = playerWins("o", plays);
        if (xWin && oWin)
            return "Error - 2 winners";
        if (xWin)
            return "X-Winner";
        if (oWin)
            return "O-Winner";
        for (String play : plays) {
            if ("".equals(play))
                return "Incomplete";
        }
        return "Tie";
    }

    public static void main(String[] args) {

        check(winner("o,x,O,,,,,,"), "Incomplete");
        check(winner("x,o,x,o,x,o,,o,x"), "X-Winner");
        check(winner("x,x,x,o,o,o,x,o,x"), "Error - 2 winners");
        check(winner("x,x,x,o,o,o,x,x,x"), "Error");
        check(winner("x,o,x,o,x,o,x,o,x"), "X-Winner");
        check(winner("x,x,x,o,,o,o,,"), "X-Winner");
        check(winner("dsfds"), "Error");
        check(winner("x,o,x,"), "Error");
        check(winner("x,o,x,a,a,a,a,a,a"), "Error");
        check(winner("o,x,o,x,x,o,x,o,x"), "Tie");
        check(winner("o,x,o,x,x,o,x,o,"), "Incomplete");

    }

    public static void check(String a, String b) {
        System.out.println(String.format("%s: %s -> %s", a.equals(b), a, b));
    }
}