how to while loop with the condition being multiple elements of an array?

[Johnny Knight]

this is the description of the problem im trying "Random Walkers: suppose that N random walkers, starting in the centre of an N-by-N grid, move one step at a time, choosing to go up down left or right with equal probability at each step. write a program to help formulate and test a hypothesis about the number of steps taken before all cells are touched."

to begin with i am just trying to do it with one walker before chucking loads in there.

so i've got a results array (yes maybe i dont need the grid array for now) and i want to loop until every value of that is true (true is where walker has been) but im just not sure how?

public class RandomWalkers
{
    public static void main(String[] args)
    {
        int N = Integer.parseInt(args[0]);
        boolean grid [][] = new boolean [N][N];
        boolean results [][] = new boolean [N][N];
        int x = N/2; int y = N/2;
        int steps = 0;
        for (int i=0;i<N;i++)
        {
            for (int j=0;j<N;j++)
            {
                while(!(results[i][j]))
                {
                    double rand =Math.random();
                    if (rand < 0.25){if (x!=N-1) x++;}
                    else if (rand <0.5){if (x!=0)x--;}
                    else if (rand<0.75){if (y!= N-1)y++;}
                    else if (rand<1.0){if (y!=0)y--;}
                    steps+=1;
                }
            }
        }
        System.out.println(steps);
    }
}

any help would be greatly appreciated. not expecting anyone to solve the problem for me, just wondered if anyone could provide links or tips on how to use multiple array values in loop conditions

[Carey Brown]

First off, I think you meant for your while() to be an if(). Second, I tend to isolate that kind of looping logic in its own small method.

private static boolean allTrue( boolean[][] array, int n )
{
    for( int i=0 ; i < n ; i++ )
        for( int j=0 ; j < n ; j++ )
            if( ! array[i][j] )
                return false;
    return true;
}

[Rob Spoor]

And to make it a bit safer:

private static boolean allTrue(boolean[][] array)
{
    for (int i = 0; i < array.length; i++)
    {
        for (int j = 0 ; j < array[i].length; j++)
        {
            if (!array[i][j])
            {
                return false;
            }
        }
    }
    return true;
}

Or using the for-each loop:

private static boolean allTrue(boolean[][] array)
{
    for (boolean[] subarray: array)
    {
        for (boolean b: subarray)
        {
            if (!b)
            {
                return false;
            }
        }
    }
    return true;
}