How to find all the blocks in a circle, in a grid, fficently?

I am trying to create a server plugin for the popular Indie game Minecraft. What I have so far is a non recursive method of finding al开发者_StackOverflow社区l the blocks 2 spaces away from the player's location. I am looking to create a method to do this efficently. I would like to be able to specify a distance. Here is what I have currently:

Block b = player.getLocation().getBlock();
b.getRelative(BlockFace.NORTH).getRelative(BlockFace.NORTH).setType(Material.FIRE);
b.getRelative(BlockFace.NORTH).getRelative(BlockFace.EAST).setType(Material.FIRE);
b.getRelative(BlockFace.EAST).getRelative(BlockFace.EAST).setType(Material.FIRE);
b.getRelative(BlockFace.EAST).getRelative(BlockFace.SOUTH).setType(Material.FIRE);
b.getRelative(BlockFace.WEST).getRelative(BlockFace.WEST).setType(Material.FIRE);
b.getRelative(BlockFace.SOUTH).getRelative(BlockFace.SOUTH).setType(Material.FIRE);
b.getRelative(BlockFace.SOUTH).getRelative(BlockFace.WEST).setType(Material.FIRE);
b.getRelative(BlockFace.NORTH).getRelative(BlockFace.WEST).setType(Material.FIRE);

Could you help me out? Thank you.

If I understand rightly for problem, you need a non-recursive algorithm to find all points on a 2D square grid at a given Manhattan distance d from the origin. Those points lie on a tiled square, and they can easily be generated in sequence. For example:

public class Points {

    public static void points(int d) {
        int px = d;
        int py = 0;
        int dx = -1, dy = 1;
        int n = d * 4;
        for( int i = 0; i < n; i++ ) {
            if( px == d && dx > 0 ) dx = -1;
            else if( px == -d && dx < 0 ) dx = 1;
            if( py == d && dy > 0 ) dy = -1;
            else if( py == -d && dy < 0 ) dy = 1;
            px += dx;
            py += dy;
            doSomething(px, py);
        }
    }

    private static void doSomething(int px, int py) {
        System.out.printf("(%2d,%2d)\n", px, py);
        // do whatever you need 
    }

    public static void main(String[] args) {
        points(2);
    }
}

This prints

( 1, 1)
( 0, 2)
(-1, 1)
(-2, 0)
(-1,-1)
( 0,-2)
( 1,-1)
( 2, 0)

You only need to code inside doSomething() your action, according to the passed coordinates.