How to reference a 2D array from a static context?

Question

Every time I call myGrid in the generateBoard method, I get the error:

non-static variable myGrid cannot be referenced from static context

To my understanding, this shouldn't happen, because I've set the array to be public and should be able to be accessed from any other class. So have I set up the array incorrectly?

import java.util.Random;

public class Zombies {
    private int Level = 1;
    private int MoveNo = 0;
    public int[][] myGrid = new int[12][12];

    public static void generateBoard() {
        Random rand = new Random();
        int i, j;
        for (i = 0; i < 12; i++) {
            for (j = 0; j < 12; j++) {
                if ( i == 6 && j == 6) {
                    myGrid[i][j] = 'P';
                }
                if (rand.nextInt(4) == 0) {
                    myGrid[i][j] = 'I';
                }
                myGrid[i][j] = 'x';
            }
        }
    }

    public static String printBoard() {
        int i, j;
        for (i = 0; i < 12; i++) {
            for (j = 0; j < 12; j++) {
                if (j == 0) {
                    System.out.print( "| " );
                }
                System.out.print( myGrid[i][j] + " " );
                if (j == 12) {
                    System.out.print( "|" );
                }
            }
        }
    }
}

Answer 1

myGrid variable is an instance variable rather than a class variable. That is, it can only be accessed by an instance of Zombies. On the other hand, the static methods (and class, a.k.a. static, variables) belong to a class, which are shared, in this case, among all Zombies instances.

Either pass myGrid (int[][]) as parameter to each of these static methods, or declare it as static.