Tic Tac Toe console program - Java

Question

I am unable to get desired output in the following code, for a console based Tic Tac Toe program.. Can anyone help me identify the error:

import java.util.Scanner;

Following is the TicTacToe class:

public class TicTacToe {
TicTacToe(){
    System.out.println("---------------------");
    System.out.println("    Tic Tac Toe     ");
    System.out.println("---------------------");
    System.out.println();
}
public static void main(String[] args) {
TicTacToe t = new TicTacToe();    

    Scanner sc = new Scanner(System.in);
    int a[][] = new int [3][3];

    for(int i=0; i<3; i++){
        for(int j=0; j<3; j++){
            a[i][j] = 2;
            System.out.print(" "+a[i][j]+" ");
        }
        System.out.println();
    }
    int count = 0;

I have used do-while loop for executing the break statements.. Although this is inefficient, nothing else struck me at that moment.

    do{
    int[][] turn1 = t.player1(a);
        t.display(turn1);
    int[][] turn2 = t.player2(turn1);
        t.display(turn2);
    int[][] turn3 = t.player1(turn2);
        t.display(turn3);
    int[][] turn4 = t.player2(turn3);
        t.display(turn4);
    int[][] turn5 = t.player1(turn4);
        t.display(turn5);
        if(t.checkwin(turn5))
            break;
    int[][] turn6 = t.player2(turn5);
        t.display(turn6);
        if(t.checkwin(turn6))
            break;
    int[][] turn7 = t.player1(turn6);
        t.display(turn7);
        if(t.checkwin(turn5))
            break;
    int[][] turn8 = t.player2(turn7);
        t.display(turn8);
        if(t.checkwin(turn5))
            break;
    int[][] turn9 = t.player1(turn8);
        t.display(turn9);
        if(t.checkwin(turn5))
            break;
    System.out.println("Game Draw");
    count++;
    }while(count ==1);
}

Following is the checkwin() method that take 2D array and returns boolean which is used for breaking or continuing the previous do-while loop.

public boolean checkwin(int m[][]){
   for(int i=0; i<3; i++){
       if(m[i][0] == m[i][1] && m[i][1] == m[i][2]){
            if(m[i][0] == 1){
               player1wins();
               return true;
            }
            else if(m[i][0] == 0){
                player2wins();
                return true;
            }
       }

The condition for following if statement shows error..

       if(m[0][i] == [1][i] && m[1][i] == m[2][i]){
            if(m[0][i] == 1){
               player1wins();
               return true;
            }
            else if(m[0][i] == 0){
                player2wins();
                return true;
            }
        }
   }

The condition for following if statement shows error..

    if(m[0][0] == [1][1] && m[1][1] == m[2][2]){ 
            if(m[0][0] == 1){
               player1wins();
               return true;
            }
            else if(m[0][0] == 0){
                player2wins();
                return true;
            }
    }
    return false;
}

Following player1wins(), player2wins() methods display if either of them won..

public static void player1wins(){
    System.out.println("1st player wins");
}

public static void player2wins(){
    System.out.println("2nd player wins");
}

Following display method which prints matrix after each turn..

public void display(int matrix[][]){
    for(int i=0; i<3; i++){
        for(int j=0; j<3; j++){
            System.out.print(" "+matrix[i][j]+" ");
        }
        System.out.println();
    }
}    

Following player1() and player2() methods takes input coordinates from the user.. They take input matrix as parameter and returns a 2D matrix..

public int[][] player1(int matrix[][]){

    Scanner sc = new Scanner(System.in);
    System.out.println("1st player's turn...");
    System.out.print("Enter x coordinate: ");
    int x = sc.nextInt();
    System.out.print("Enter y coordinate: ");
    int y = sc.nextInt();

    matrix[x][y] = 1;
    return matrix;         
}

public int[][] player2(int matrix[][]){

    Scanner sc = new Scanner(System.in);
    System.out.println("2nd player's turn...");
    System.out.print("Enter x coordinate: ");
    int x = sc.nextInt();
    System.out.print("Enter y coordinate: ");
    int y = sc.nextInt();

    matrix[x][y] = 0;
    return matrix;         
}    
}

Moreover, if anyone can help me optimize this console based tic-tac-toe java code or post any link for the same, it would be of great help.. Thanks, in advance..

Answer 1

Your if statement looks to be syntactically incorrect:

if(m[0][i] == [1][i] && m[1][i] == m[2][i]){

The [1][i] is missing an m before it. It should be this:

if(m[0][i] == m[1][i] && m[1][i] == m[2][i]){

The same applies to the other if statement:

Change

if(m[0][0] == [1][1] && m[1][1] == m[2][2]){ 

to

if(m[0][0] == m[1][1] && m[1][1] == m[2][2]){ 

These are both in your checkwin() method.

---

EDIT: Another bug: Your code checks the board for turn 5 on each turn. (For turn 7, 8, and 9, this is the case. 6 is fine).

Also, rather than using a do loop, you could just use return instead of break.

But I would recommend eliminating the repetition of that bit entirely: change it to this, using for and a 3d array.

int[][][] turns = new int[10][][];
turns[0] = a;

// We start at 1 rather than 0 because the first value is a.
for (int i = 1; i <= 9; i++) {
    if (i % 2 == 1) { // Odd-numbered turn
        turns[i] = t.player1(turns[i - 1]);
    } else { // Even-numbered turn
        turns[i] = t.player2(turns[i - 1]);
    }

    t.display(turns[i]);

    if (t.checkwin(turns[i])) {
        return;
    }
}

System.out.println("Game Draw");

This is much cleaner-looking, and should work well.