DouKaku?

import java.util.Random;

public class TicTacToe {
    public static final int SIZE = 3;

    private final Mark[][] fields_ = new Mark[SIZE][SIZE];
    private final Pair[][] lines_ = new Pair[][] {
            {new Pair(0,0), new Pair(0,1), new Pair(0,2)},
            {new Pair(1,0), new Pair(1,1), new Pair(1,2)},
            {new Pair(2,0), new Pair(2,1), new Pair(2,2)},
            {new Pair(0,0), new Pair(1,0), new Pair(2,0)},
            {new Pair(0,1), new Pair(1,1), new Pair(2,1)},
            {new Pair(0,2), new Pair(1,2), new Pair(2,2)},
            {new Pair(0,0), new Pair(1,1), new Pair(2,2)},
            {new Pair(2,2), new Pair(1,1), new Pair(0,0)},
    };


    public TicTacToe() {
        for (int x = 0; x < SIZE; x++) {
            for (int y = 0; y < SIZE; y++) {
                fields_[x][y] = Mark.E;
            }
        }
    }

    public Mark getMark(Pair pair) {
        return fields_[pair.x][pair.y];
    }
    public void setMark(Pair pair, Mark mark) {
        fields_[pair.x][pair.y] = mark;
    }

    public boolean nextStep(Pair pair, Mark mark) {
        if (getMark(pair) != Mark.E) return false;
        setMark(pair, mark);
        return true;
    }

    public Mark isEndGame() {
        for (Pair[] row: lines_) {
            Mark m = null;
            boolean isSame = true;
            for (Pair cell: row) {
                Mark mark = fields_[cell.x][cell.y];
                if (m == null) {
                    m = mark;
                    continue;
                }
                if (m != mark) {
                    isSame = false;
                    break;
                }
            }
            if (isSame) return m;
        }
        return Mark.E;
    }


    public static void main(String[] args) {
        Player player1 = new RandomPlayer(Mark.O, "Player1");
        Player player2 = new RandomPlayer(Mark.X, "Player2");

        int maxTurn = TicTacToe.SIZE * TicTacToe.SIZE;
        int[] result = new int[3];
        for (int round = 0; round < 10000; round++) {
            TicTacToe game = new TicTacToe();
            for (int turn = 0; turn <= maxTurn; turn++) {
                if (turn == maxTurn) {
                    result[2]++;
                    break;
                } else if (turn % 2 == 0) {
                    player1.put(game);
                } else {
                    player2.put(game);
                }
                Mark mark = game.isEndGame();
                if (mark == Mark.O) {
                    result[0]++;
                    break;
                } else if (mark == Mark.X) {
                    result[1]++;
                    break;
                }
            }
        }

        System.out.println("Result:");
        System.out.printf("%s won: %d%n", player1.name, result[0]);
        System.out.printf("%s won: %d%n", player2.name, result[1]);
        System.out.printf("draw game  : %d%n", result[2]);
    }
}

enum Mark {
    E { @Override public Mark getOpponent() { return E; } },
    O { @Override public Mark getOpponent() { return X; } },
    X { @Override public Mark getOpponent() { return O; } };

    public abstract Mark getOpponent();
}
class Pair {
    public final int x;
    public final int y;

    public Pair(int x, int y) {
        this.x = x;
        this.y = y;
    }
}


abstract class Player {
    public final Mark mark;
    public final String name;

    public Player(Mark mark, String name) {
        this.mark = mark;
        this.name = name;
    }

    public abstract void put(TicTacToe game);
}

class RandomPlayer extends Player {
    private final Random random_ = new Random();

    public RandomPlayer(Mark mark, String name) {
        super(mark, name);
    }

    @Override
    public void put(TicTacToe game) {
        for (;;) {
            Pair pair = getNextPair();
            boolean res = game.nextStep(pair, mark);
            if (res) break;
        }
    }
    private Pair getNextPair() {
        return new Pair(random_.nextInt(TicTacToe.SIZE), random_.nextInt(TicTacToe.SIZE));
    }
}