A little help in TicTacToe

Question

I wrote this code that works and does everything alright and plays the game, but i need the game to be able to check if a square is already occupied and tell the user to input again. I am not doing well there. here's what i have...
// tic tac toe game
import java.util.Scanner; // import the scanner
public class TicTacToe
{ // start of class
     public static String board [][] = new String [3][3]; // create a 3x3 array called board
     public static void main(String[] args) //main method
     { // start main
          Scanner input = new Scanner( System.in ); // create scanner to read inputs
          String name1; // player1's name
          String name2; // player2's name
          String current = "O";// the current mark
          int choice;//the choice user inputs
          int cheat; // cheatcode
          int moveCount = 0; // count the number of moves made
          int check = 0;
          System.out.println( "Enter Player1's name: " );//prompt
          name1 = input.nextLine();//read input
        System.out.println( "Enter Player2's name: " );//prompt
          name2 = input.nextLine();//read input
          for ( int i = 0; i < 3; i++)
          { //start of loop
               for ( int j = 0; j < 3; j++)
               {//start of loop
                    board[i][j] = " "; // initializes board to empty spaces
               }//end of loop
          }//end of loop
          System.out.println(); // the next few lines are dedicated to print a board
          System.out.println ( "   ************************" );
          for ( int row = 0; row < 3; row++ )
          {//start of loop
               for ( int column = 0; column < 3; column++ )
               {//start of loop
                    System.out.printf ( "   *       *       *      *\n" );
               }//end of loop
          System.out.println ( "   ************************" );          
          }//end of loop
        int winner = 0; // winner
          while (winner == 0)
          {//start of gignormous loop
               if (current == ("O")) // switch between players
                    current = "X";
                    System.out.printf( "%s, make your move.", name1 );//prompt
                    choice = input.nextInt();//read input
                    ++moveCount;
                if ( moveCount == 9)
                winner = 5;
                    if ( choice <= 0 || choice >9 )// prevent user from going crazy and input weird numbers
                         System.out.printf( "%s, can't do that homey.", name1 );//prompt
                        choice = input.nextInt();//read input
                         if ( choice == 333)
                       winner = 3;
                    else
                    xmark(choice); // mark x by passing choice to xmark
                    winner = CheckOneWin ( winner ); // check for win for player1...passes winner...blah blah
                    for ( int row1 = 0; row1 != 3; row1++ )
                   System.out.println ( "   *************************" );
                   System.out.println ( "   *       *       *       *" );
                   for ( int column1 = 0; column1 != 3; column1++ )
                        System.out.printf ( "%4s%4s" , "*" , board[row1][column1] );
                   System.out.printf ( "%s\n%s\n" , "   *" , "   *       *       *       *" );
                   System.out.println ( "   *************************" );
                   else
                    current = "O"; // switch back to o
                   System.out.printf( "%s, make your move.", name2 );//prompt
                  choice = input.nextInt();//read input
                  ++moveCount;
                  if ( moveCount == 9 )
                  winner = 5;
                  if ( choice <= 0 || choice > 9 ) // prevent user from going crazy
                   System.out.printf( "%s, can't do that homey.", name2 );//prompt
                   choice = input.nextInt();//read input
                   if ( choice == 333)
                   winner = 3;
                   omark(choice); // pass choice to method omark
                   winner = CheckTwoWin ( winner ); // check for winner by passing winner to method CheckTwoWin
                  for ( int row2 = 0; row2 != 3; row2++ )
                   System.out.println ( "   *************************" );
                   System.out.println ( "   *       *       *       *" );
                   for ( int column2 = 0; column2 != 3; column2++ )
                        System.out.printf ( "%4s%4s" , "*" , board[row2][column2] );
                   System.out.printf ( "%s\n%s\n" , "   *" , "   *       *       *       *" );
                   System.out.println ( "   *************************" );
          if (winner == 1) // tells that player1 has won
               System.out.printf("\n%s wins, way to go homey!\n", name1);
          if (winner == 3) // tells that player1 has won with cheat code
               System.out.printf("\n%s wins...with a cheat...don't you have any real skills?\n", name1);
          if (winner == 2) // tells that player2 has won
               System.out.printf("\n%s wins, way to go homey!\n", name2);
          if (winner == 4) // tells that player2 has won with cheat code
               System.out.printf("\n%s wins...with a cheat...don't you have any real skills?\n", name2);
          if (winner == 5) // tells that a tie occurs
               System.out.printf("The game is tied, looks like %s and %s are evenly matched...\n", name1, name2);
          }//end of hugmongus while loop
     } // end method main
        public static void xmark ( int x ) // use x to recieve choice
              int thingy = x; // thingy is the private copy of x
              switch ( thingy ) // switch for thingy
                   case 1:
                        if (board[0][0] == "O")
                        System.out.println("can't override dude...");
                        else
                         board[0][0] = "X"; // mark X on board [0][0] if case is
                         break;
                   case 2:
                        if (board[0][1] == "O")
                        System.out.println("can't override dude...");
                        else
                        board[0][1] = "X"; // mark X...board[0][1]...
                        break;
                   case 3:
                        if (board[0][2] == "O")
                        System.out.println("can't override dude...");
                        else
                        board[0][2] = "X"; // blah
                        break;
                   case 4:
                        if (board[1][0] == "O")
                        System.out.println("can't override dude...");
                        else
                         board[1][0] = "X"; //blah
                        break;
                   case 5:
                        if (board[1][1] == "O")
                        System.out.println("can't override dude...");
                        else
                         board[1][1] = "X"; // yadayadyada
                        break;
                   case 6:
                        if (board[1][2] == "O")
                        System.out.println("can't override dude...");
                        else
                         board[1][2] = "X";
                        break;
                   case 7:
                        if (board[2][0] == "O")
                        System.out.println("can't override dude...");
                        else
                         board[2][0] = "X";
                        break;
                   case 8:
                        if (board[2][1] == "O")
                        System.out.println("can't override dude...");
                        else
                         board[2][1] = "X";
                        break;
                   case 9:
                        if (board[2][2] == "O")
                        System.out.println("can't override dude...");
                        else
                         board[2][2] = "X";
                        break;
          public static void omark ( int o ) // o recieves choice
              int thingy = o; // same thing as last method
              switch ( thingy ) // switch for thingy
                   case 1:
                        if (board[0][0] == "X")
                        System.out.println("can't override dude...");
                        else
                         board[0][0] = "O"; // mark X on board [0][0] if case is
                         break;
                   case 2:
                        if (board[0][1] == "X")
                        System.out.println("can't override dude...");
                        else
                        board[0][1] = "O"; // mark X...board[0][1]...
                        break;
                   case 3:
                        if (board[0][2] == "X")
                        System.out.println("can't override dude...");
                        else
                        board[0][2] = "O"; // blah
                        break;
                   case 4:
                        if (board[1][0] == "X")
                        System.out.println("can't override dude...");
                        else
                         board[1][0] = "O"; //blah
                        break;
                   case 5:
                        if (board[1][1] == "X")
                        System.out.println("can't override dude...");
                        else
                         board[1][1] = "O"; // yadayadyada
                        break;
                   case 6:
                        if (board[1][2] == "X")
                        System.out.println("can't override dude...");
                        else
                         board[1][2] = "O";
                        break;
                   case 7:
                        if (board[2][0] == "X")
                        System.out.println("can't override dude...");
                        else
                         board[2][0] = "O";
                        break;
                   case 8:
                        if (board[2][1] == "X")
                        System.out.println("can't override dude...");
                        else
                         board[2][1] = "O";
                        break;
                   case 9:
                        if (board[2][2] == "X")
                        System.out.println("can't override dude...");
                        else
                         board[2][2] = "O";
                        break;
          public static int CheckOneWin( int win1 ) // recieves winner with win1
               int win2 = win1; // win2 = new copy of win1
               if ( ( board[0][0] == "X" ) && ( board [0][1] == "X" ) && ( board [0][2] == "X" ) ) // if these 3 spaces are all X
                    win2 = 1; // player1 wins and win2 is set to 1
               if ( ( board[1][0] == "X" ) && ( board [1][1] == "X" ) && ( board [1][2] == "X" ) ) // same thing again
                    win2 = 1; 
               if ( ( board[2][0] == "X" ) && ( board [2][1] == "X" ) && ( board [2][2] == "X" ) )
                    win2 = 1;
               if ( ( board[0][0] == "X" ) && ( board [1][0] == "X" ) && ( board [2][0] == "X") )
                    win2 = 1;
               if ( ( board[0][1] == "X" ) && ( board [1][1] == "X" ) && ( board [2][1] == "X" ) )
                    win2 = 1;
               if ( ( board[0][2] == "X" ) && ( board [1][2] == "X" ) && ( board [2][2] == "X" ) )
                    win2 = 1;
               if ( ( board[0][0] == "X" ) && ( board [1][1] == "X" ) && ( board [2][2] == "X" ) )
                    win2 = 1;
               if ( ( board[0][2] == "X" ) && ( board [1][1] == "X" ) && ( board [2][0] == "X" ) )
                    win2 = 1;
               return win2; // returns win2
          public static int CheckTwoWin( int win3 )// recieve winner with win3
               int win4 = win3;//blah
               if ( ( board[0][0] == "O" ) && ( board [0][1] == "O" ) && ( board [0][2] == "O" ) )//all that good stuff
                    win4 = 1;
               if ( ( board[1][0] == "O" ) && ( board [1][1] == "O" ) && ( board [1][2] == "O" ) )
                    win4 = 1; 
               if ( ( board[2][0] == "O" ) && ( board [2][1] == "O" ) && ( board [2][2] == "O" ) )
                    win4 = 1;
               if ( ( board[0][0] == "O" ) && ( board [1][0] == "O" ) && ( board [2][0] == "O" ) )
                    win4 = 1;
               if ( ( board[0][1] == "O" ) && ( board [1][1] == "O" ) && ( board [2][1] == "O" ) )
                    win4 = 1;
               if ( ( board[0][2] == "O" ) && ( board [1][2] == "O" ) && ( board [2][2] == "O" ) )
                    win4 = 1;
               if ( ( board[0][0] == "O" ) && ( board [1][1] == "O" ) && ( board [2][2] == "O" ) )
                    win4 = 1;
               if ( ( board[0][2] == "O" ) && ( board [1][1] == "O" ) && ( board [2][0] == "O" ) )
                    win4 = 1;
               return win4; //returns win4
}//end of this huge and hard classNow if a user tries to override a already occupied square, it will say "dude, can't override..." and automically hand the move to next player without letting the user move again...someopne please help me...

Answer 1

Boolean is a primitive that can have two values - true or false. Run this and see if you understand:
class OddsEvens {
    int[] numbers = {1,2,4,5,7,8};
    public void checkNumbers() {
        for(int index = 0; index < numbers.length; index++) {
            System.out.print(numbers[index] + " is ");
            if(isEven(numbers[index])) {
                System.out.println("even");
            } else {
                System.out.println("odd");
    private boolean isEven(int value) {
        if(value %2 == 0) {
            return true;
        } else {
            return false;
    public static void main(String[] args) {
        OddsEvens oe = new OddsEvens();
        oe.checkNumbers();
}