Question

I am used to coding in PHP but I am not really proficient with Java and this has been a problem for some time now. I expect it to be a fairly easy solution, however I cannot find any good example code any way I search it, so here goes:

I am programming a game that takes place in a 2d random generated infinite world on a tile based map (nitpicking: I know it will not be truly infinite. I just expect the world to be quite large). The usual approach of map[x][y] multidimensional array started out as a basic idea, but since Java does not provide a way for non-integer (i.e. negative) array key shenanigans like PHP does, I cannot properly have a (-x,+x,-y,+y) coordinate system with array keys.

I need to be able to find the objects on a tile at a specific x,y coordinate as well as finding “adjacent tiles” of a certain tile. (Trivial if I can getObjectAt(x,y), I can get(x+1,y) and so on)

I have read about quad trees and R-trees and the like. The concept is exciting, however I haven’t seen any good, simple example implementation in Java. And besides I am not really sure if that is what I need exactly.

Any advice is welcome

Thank you

Answer 1

I came to this thread with the same problem, but my solution was to use Map/HashMaps, but these are one dimensional.

To overcome this, instead of using a map within a map (which would be messy and very inefficient) I used a generic Pair class (not something that you’ll find in the stock java library) although you could replace this with a Position class (virtually the same code, but not generic, instead integers or floats).

So when defining the map: Map<Pair, Tile> tiles = new HashMap<Pair, Tile>;

For placing tile objects onto the map I used tiles.put(new Pair(x, y), new GrassTile()); and for retrieving the object tiles.get(new Pair(x, y));.

[x/y would be any coordinate you wish to place (this allows negative coordinates without any mess!), “new GrassTile()” is just an example of placing a tile of a certain type during map creation. Obviously – as previously stated – the Pair class is replacable.]

Why not ArrayLists you may ask? Because array lists are much more linear than mapping, and in my opinion are more difficult to add and retrieve tiles, especially on 2 Dimensions.

Update:

For anyone wondering why there isn’t a Pair() class in Java, here’s an explanation.