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Editorial Team
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Asked: 2026-05-11T18:08:34+00:00

I have Tile s which represent the tiles in a game’s 2-dimensional world. The

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I have Tiles which represent the tiles in a game’s 2-dimensional world. The tiles can have walls on any number of their 4 sides. I have something like this at the moment:

interface Tile {
    boolean isWallAtTop();
    boolean isWallAtRight();
    boolean isWallAtLeft();
    boolean isWallAtBottom();
}

Somewhere else I also have 16 images, one for each possible tile wall configuration. Something like this:

static final Image WALLS_ALL_AROUND = ...
static final Image WALL_ON_TOP_AND_RIGHT = ...
/* etc etc all 16 possibilities */

I want to write a 

static Image getWallImage(Tile tile)

What I’d like to avoid is the torture of going through the possibilities like

if (tile.isWallTop && tile.isWallRight 
    && !tile.isWallBottom && !tile.isWallLeft) {
    return WALL_ON_TOP_AND_RIGHT;
}

Does anyone know a cuter way to do this?

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1 Answer

  1. Editorial Team

    Go go gadget bitmasks. Use a 4 bit mask for each tile, stating which side has a wall.

    A B C D

    Bit A indicates a wall on the top, B the right, C the bottom, D the left. Define constants to help you that you can just logically intersect with the mask, i.e.

    if (tile.Walls & (WALL_LEFT | WALL_RIGHT))
  // Do stuff

    For finding the image, this 4 bit mask produces the 16 possibilities. Use it as an index into an images “array”, so you can directly find the correct image without any effort.

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