Thread: Java chunk negative number problem

I've got a tile based map, which is divided in chunks. I got a method, which puts tiles in this map and with positive numbers it's working. But when using negative numbers it wont work. This is my setTile method:

public static void setTile(int x, int y, Tile tile)
    	{
    		int chunkX = (int) Math.floor((float) x / (float) Chunk.CHUNK_SIZE), chunkY = (int) Math.floor((float) y / (float) Chunk.CHUNK_SIZE);
 
                IntPair intPair = new IntPair(chunkX, chunkY);
 
    			world.put(intPair, new Chunk(chunkX, chunkY));
 
    		world.get(intPair).setTile(x - chunkX * Chunk.CHUNK_SIZE, y - chunkY * Chunk.CHUNK_SIZE, tile);
    	}

This is the setTile method in the chunk class (CHUNK_SIZE is a constant with the value 64):
The tiles array is a 2 dimensional 64*64 array

public void setTile(int x, int y, Tile t)
    	{
    		if (x >= 0 && x < CHUNK_SIZE && y >= 0 && y < CHUNK_SIZE)
    			tiles[x][y] = t;
    	}

The setTile method places a tile in a chunk. But when using a negative value a weird result is created. With e.g. x 53 it should place the tile in the chunk at the x position 0 and the chunk-array position 53. With the x value 87 it should place it in the chunk at x position 1 and the chunk-array position 23. These two examples work. But when using e.g. -45 it should place it in the chunk at x -1 and chunk-array position 18 which is not the case.

What's wrong with my code?

But when using a negative value a weird result is created.

Sometimes the result for the chunk-array position is 128 sometimes 64.

It's kind of hard to explain. I'm using chunks in a tile based game. When using a absolute x or y value, it should place it in a relative x or y value in the chunk. However, when using a negative value as x position (maybe y too, but I don't need negative y positions) the result is a strange value out of the bounds of the array.

Wow... When programming the problem-showing-program the problem somehow solved itself