TicTacToe.java

import java.util.*;
public class TicTacToe {
  int arr[][] = new int[3][3];
  //0 for empty, 1 for X and 2 for O
  public static void main(String args[]) {
    TicTacToe game = new TicTacToe();
    while(true) {
      game.display();
      game.check();
      game.input(1);
      game.display();
      game.check();
      game.input(2);
    }
  }

  public TicTacToe() {
    for(int i = 0; i < 3; i++) {
      for(int j = 0; j < 3; j++) {
        arr[i][j] = 0;
      }
    }
  }

  public void input(int plyr_id) {
    Scanner sc = new Scanner (System.in);
    int i = -1, j = -1;
    System.out.println("Enter the coordinates player " + plyr_id);
    try {
      i = sc.nextInt();
      j = sc.nextInt();
      if(isValid(i,j))
        arr[i][j] = plyr_id;
      else {
        System.out.println("Invalid Input, Try Again !!");
        input(plyr_id);
      }
    } catch(InputMismatchException e) {
      System.out.println("Invalid input, only integers are allowed. Try Again !!");
      input(plyr_id);
    }
  }

  public boolean gameOver() {
    for(int i = 0; i < 3; i++) {
      for(int j = 0; j < 3; j++) {
        if(arr[i][j] == 0)
          return false;
      }
    }
    return true;
  }

  public boolean isValid(int i, int j) {
    return (i < 3 && j < 3 && i >= 0 && j >=0 && arr[i][j]==0);
  }

  public void display() {
    for(int i = 0; i < 3; i++) {
      for(int j = 0; j < 3; j++) {
        if(arr[i][j] == 0)
          System.out.print("|   |");
        if (arr[i][j] == 1)
          System.out.print("| X |");
        if(arr[i][j] == 2)
          System.out.print("| O |");
      }
      if(i != 2)
        System.out.print("\n---------------\n");
      else
        System.out.println();
    }
  }

  public void check() {
    for(int i = 0 ; i < 3; i++) {
      //Checking Horizontal win conditions
      if(arr[i][0] == arr[i][1] && arr[i][0] == arr[i][2]) {
        if(arr[i][0] == 1) {
          System.out.println("X Won the match");
          System.exit(0);
        } else if(arr[i][0] == 2) {
          System.out.println("O won the match");
          System.exit(0);
        }
      }
      //Checking Vertical win conditions
      if(arr[0][i] == arr[1][i] && arr[0][i] == arr[2][i]) {
        if(arr[0][i] == 1) {
          System.out.println("X Won the match");
          System.exit(0);
        } else if(arr[0][i] == 2) {
          System.out.println("O won the match");
          System.exit(0);
        }
      }
      //Checking Diagonally 1
      if(arr[0][0] == arr[1][1] && arr[0][0] == arr[2][2]) {
        if(arr[0][0] == 1) {
          System.out.println("X Won the match");
          System.exit(0);
        } else if(arr[0][0] == 2) {
          System.out.println("O won the match");
          System.exit(0);
        }
      }
      //Checking Diagonally 2
      if(arr[0][2] == arr[1][1] && arr[0][2] == arr[2][0]) {
        if(arr[0][2] == 1) {
          System.out.println("X Won the match");
          System.exit(0);
        } else if(arr[0][2] == 2) {
          System.out.println("O won the match");
          System.exit(0);
        }
      }
    }
    if(gameOver()) {
      System.out.println("Its a tie");
      System.exit(0);
    }
  }
}