Code golfed tic tac toe. Doesn't allow moving in occupied squares and detects wins and ties. Didn't exactly stick to what we've covered so for. Don't try this at home.

TicTacToe.java

import java.util.Scanner;

public class TicTacToe {

  public static void printBoard(int board) {
    System.out.print("\033[2J\033[0;0H");
    int pieces = board >> 4;
    for (int i = 0; i < 9; i++) {
      System.out.print(" " + (i + "XO").charAt((pieces >> i & 1 | pieces >> i + 8 & 2) & 3) + " ");
      if (i % 3 < 2) {
        System.out.print("|");
      } else {
        System.out.println(i / 3 < 2 ? "\n---+---+---" : "\n");
      }
    }
  }

  public static int getMove(int board, Scanner input) {
    int m = input.nextInt();
    while (((board >> m | board >> (m + 9)) & 1) == 1) {
      System.out.println("Square occupied. Please try again.");
      m = input.nextInt();
    }
    return m;
  }

  public static boolean winner(int player) {
    for (int i = 0; i < 3; i++) {
      if (((7 << 3 * i) & player) == (7 << 3 * i)) return true;
      if (((73 << i) & player) == (73 << i)) return true;
    }
    return ((273 & player) == 273 || (84 & player) == 84);
  }

  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    int board = 0;
    while (!winner(board >> (4 + ((~board & 1) * 9))) && (board & 15) < 9) {
      printBoard(board);
      board |= 16 << getMove(board >> 4, input) + (board & 1) * 9;
      board++;
    }
    printBoard(board);
    if (winner(board >> (4 + (~board & 1) * 9))) {
      System.out.println("\n" + "OX".charAt(board & 1) + " wins!\n");
    } else {
      System.out.println("\nTie!\n");
    }
  }
}