Question

I need help with this method (public static int computer_move(int board[][])) . When I run it and play the compute.The computer enters the 'O' in a location that the user has all ready enter it sometimes. I need to fix it where the computer enters the 'O' in a location the user has not enter the "X' already

package tictactoe;

import java.util.Scanner;

public class TicTacToeGame {

static final int EMPTY = 0;

static final int NONE = 0;

static final int PLAYER1 = 1;

static final int COMPUTER = 2;

static final int TIE = 3;

static final int PLAYER2 = 4;

public static void main(String[] args) {

int turn = PLAYER1;

int[][] board = new int[3][3];

int move;

int winner;

int gameChoice=0;

Scanner input=new Scanner(System.in);

System.out.println("**********Welcome to the game of TIC-TAC-TOE**********");

System.out.println("Choose the number 0. for: You Vs. Computer");

System.out.println("Choose the number 1. for: Human Vs. Human");

try { gameChoice = input.nextInt();

}

catch(Exception e){

System.out.println("Type 0. or 1.");

System.exit(0); }

if (gameChoice==0)

System.out.println("Its You Vs. Computer!");

else if (gameChoice==1)

System.out.println("1. User1 Vs. User2");

else { System.out.println("Default: 0");

gameChoice=0;

System.out.println("Its You Vs. Computer!");

}

System.out.println("Enter 1-9 to indicate your move");

System.out.println("1|2|3"); System.out.println("-----");

System.out.println("4|5|6");

System.out.println("-----");

System.out.println("7|8|9");

while(true) { if(turn == PLAYER1) {

if(gameChoice==0)

System.out.println("Your move");

else

System.out.println("User1's move");

move = 0;

while (move<1 || move>9 || board[(move-1)/3][(move-1)%3] != EMPTY) {

System.out.println("Please enter your move(1-9): ");

move = input.nextInt();

}

}

else if(turn == PLAYER2) {

System.out.println("User2's move");

move = 0;

while (move<1 || move>9 || board[(move-1)/3][(move-1)%3] != EMPTY) {

System.out.println("Please enter your move(1-9): ");

move = input.nextInt();

}

}

else {

move = computer_move(board);

System.out.println("Computer move: " + move);

}

board[(int)((move-1)/3)][(move-1)%3] = turn;

print_board(board);

winner = checkWinner(board);

if(winner != NONE) break;

if(turn == PLAYER1)

if (gameChoice==0)

turn = COMPUTER;

else turn = PLAYER2;

else turn = PLAYER1;

}

switch(winner) {

case PLAYER1:

if(gameChoice==0)

System.out.println("You won!");

else

System.out.println("User 1 won!");

break;

case PLAYER2: System.out.println("User 2 won!");

break;

case COMPUTER: System.out.println("Computer won!");

break;

default: System.out.println("Tie!"); break; }

}

public static void print_board(int[][] board) {

System.out.print(printChar(board[0][0]));

System.out.print("|");

System.out.print(printChar(board[0][1]));

System.out.print("|");

System.out.println(printChar(board[0][2]));

System.out.println("-----");

System.out.print(printChar(board[1][0]));

System.out.print("|");

System.out.print(printChar(board[1][1]));

System.out.print("|");

System.out.println(printChar(board[1][2]));

System.out.println("-----");

System.out.print(printChar(board[2][0]));

System.out.print("|");

System.out.print(printChar(board[2][1]));

System.out.print("|");

System.out.println(printChar(board[2][2]));

}

public static char printChar(int b) {

switch(b) {

case EMPTY:

return ' ';

case PLAYER1:

return 'X';

case PLAYER2:

return 'O';

case COMPUTER:

return 'O'; }

return ' '; }

public static int checkWinner(int[][] board) {

if((board[0][0] == board[0][1]) && (board[0][1] == board[0][2]))

return board[0][0];

if((board[1][0] == board[1][1]) && (board[1][1] == board[1][2]))

return board[1][0];

if((board[2][0] == board[2][1]) && (board[2][1] == board[2][2]))

return board[2][0];

if((board[0][0] == board[1][0]) && (board[1][0] == board[2][0]))

return board[0][0];

if((board[0][1] == board[1][1]) && (board[1][1] == board[2][1]))

return board[0][1];

if((board[0][2] == board[1][2]) && (board[1][2] == board[2][2]))

return board[0][2];

if((board[0][0] == board[1][1]) && (board[1][1] == board[2][2]))

return board[0][0];

if((board[0][2] == board[1][1]) && (board[1][1] == board[2][0]))

return board[0][2];

if(board[0][0] == EMPTY || board[0][1] == EMPTY || board[0][2] == EMPTY || board[1][0] == EMPTY || board[1][1] == EMPTY || board[1][2] == EMPTY || board[2][0] == EMPTY || board[2][1] == EMPTY || board[2][2] == EMPTY)

return NONE;

return TIE; }

public static int computer_move(int[][] board) {

int move = (int)(Math.random()*9);

while(board[move/3][move%3] != EMPTY)

move = (int)(Math.random()*9);

return move;

}

}