An answer to the StackOverflow and Learneroo question: http://www.learneroo.com/courses/29/nodes/221

DistanceZ.java

import java.util.*;

class DistanceZ {
	
	
	static void minArray(int[][] square){
		int w = square.length;
		
		for(int times = 0; times<w; times++){
			for(int i =0; i<w;i++){
				for(int j=0;j<w;j++){
					square[i][j] = minCell(square, i, j);
				}
			}
		}		
		printArray(square);		
	}
	
	private static void printArray(int[][] square) {
		int w = square.length;		
		for(int i =0; i<w;i++){
			for(int j=0;j<w;j++){
				System.out.print(square[i][j] + " ");
			}
			System.out.println("");
		}
		
	}

	static int minCell(int[][] square, int i, int j){
		int left,right,up,down = 1000;
		int min = square[i][j];
		if(i>0){
			left = square[i-1][j] +1;
			if(left<min)
				min=left;
		}
		if(i<square.length-1)	{
			right = square[i+1][j] +1;
				if(right<min)
					min=right;
		}
		if(j>0)	{
			up = square[i][j-1] + 1;
			if(up<min)
				min=up;
		}
		if(j<square.length-1) {
			down = square[i][j+1] + 1;
			if(down<min)
				min=down;
		}
		return min;		
	}
	
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int t = in.nextInt();
		for(int times=0;times<t;times++){
    		int w = in.nextInt();
    		int[][] square = new int[w][w];		
    		for(int i =0; i<w;i++){
    			for(int j=0;j<w;j++){
    				square[i][j] = in.nextInt();
    			}
    		}
    		minArray(square);
		}
	}
}