Question

What I am doing is creating a command line “game” where there is a 3×3 grid (Array) where you can move a “1” through it by typing the direction (up, down, left, right).

For example:

0 0 0

0 1 0

0 0 0

I’ve made it so if the 1 is on the edge of the array it is not allowed to move out of the boundaries (read: resulting in an out of index error).

I’m completely lost as whenever I try to move right, I receiving the following:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 3
at Logic.setMove(Logic.java:87)
at Logic.getMove(Logic.java:10)
at GridGameMain.main(GridGameMain.java:13)

Here’s my code:

public class GridGameMain {
static int[][] board = new int[3][3];
public static void main(String[] args){

    board[(int) (Math.random() * 2.5)][(int) (Math.random() * 2.5)] = 1;
    for (int i =0; i < 3; i++) {
        for (int j = 0; j < 3; j++) {
        System.out.print(" " + board[j][i]);
        }
        System.out.println("");
        }
    Logic l = new Logic();
    l.getMove();

}

}


import java.util.Scanner;

public class Logic extends GridGameMain{
void getMove(){     //takes user input then calls setMove

    String direction;  //string to hold the direction
    Scanner user_input = new Scanner(System.in);   
    direction = user_input.next();    
    Logic l = new Logic();      
    l.setMove(direction);        

}
void setMove(String direction){ //called when user presses enter upon typing a move
    Logic l = new Logic();

    if(direction.equals("up")){

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

            System.out.println("Invalid move!");

            l.getMove();

        }else{
        for(int a = 0; a < 3; a++){
            for(int b = 0; b < 3; b++){
                if(board[a][b] == 1){
                    board[a][b-1] = 1;
                    board[a][b] = 0;
                    break;
                }
            }
        }
        l.printBoard();
        System.out.println("you moved up");
        l.getMove();
        }
    }

    if(direction.equals("down")){           
        if(board[0][2] == 1 || board[1][2] == 1 || board[2][2] == 1 ){
            System.out.println("Invalid move!");
            l.getMove();
        }else{
            for(int a = 0; a < 3; a++){
                for(int b = 0; b < 3; b++){
                    if(board[a][b] == 1){
                        board[a][b+1] = 1;
                        board[a][b] = 0;
                        break;
                    }
                }
            }
            l.printBoard();
        System.out.println("you moved down");
        l.getMove();
        }
    }
    if(direction.equals("left")){
        if(board[0][0] == 1 || board[0][1] == 1 || board[0][2] == 1 ){
            System.out.println("Invalid move!");
            l.getMove();
        }else{
            for(int a = 0; a < 3; a++){
                for(int b = 0; b < 3; b++){
                    if(board[a][b] == 1){
                        board[a-1][b] = 1;
                        board[a][b] = 0;
                        break;
                    }
                }
            }
            l.printBoard();

        System.out.println("you moved left");
        l.getMove();
        }
    }
    if(direction.equals("right")){
        if(board[2][0] == 1 || board[2][1] == 1 || board[2][2] == 1 ){
            System.out.println("Invalid move!");
            l.getMove();
        }else{
            for(int a = 0; a < 3; a++){
                for(int b = 0; b < 3; b++){
                    if(board[a][b] == 1){
                        board[a+1][b] = 1;
                        board[a][b] = 0;
                        break;
                    }
                }
            }

        l.printBoard();
        System.out.println("you moved right");
        l.getMove();
        }
    }
}
void printBoard(){
    for (int i =0; i < 3; i++) {
        for (int j = 0; j < 3; j++) {
        System.out.print(" " + board[j][i]);
        }
        System.out.println("");
        }
}
}

I’m just not sure why I can’t move right when I can move up, down, and left just fine. Please tell me I’m not crazy!

Answer 1

I think the trouble is, you check to make sure the 1 is not on the far right, and then you start shifting things right. That means that, if your 1 was on the column 0, it’s moved to column 2, then at the next and last iteration, it’s moved to column 3.

Also, are you sure this doesn’t happen when you go down?
This doesn’t happen going down because, as @Keppil says, you break out of the “rows” (relevant) loop, while going right, you break out of the columns one, which is not what you wanted.

Also, you can use tags to break out of whatever loop you want. Here’s how.