So, I'm developing a 2D, tile based game and a map maker thingy - all in Java.

The problem is that recently I've been having some memory issues when about 4 maps are loaded. Each one of these maps are composed of 128x128 tiles and have 4 layers (for details and stuff).

I already spent a good amount of time searching for solutions and the best thing I found was run-length enconding (RLE). It seems easy enough to use with static data, but is there a way to use it with data that is constantly changing, without a big drop in performance?

In my maps, supposing I'm compressing the columns, I would have 128 rows, each with some amount of data (hopefully less than it would be without RLE). Whenever I change a tile, that whole row would have to be checked and I'm affraid that would slow down too much the production (and I'm in a somewhat tight schedule).

Well, worst case scenario I work on each map individually, and save them using RLE, but it would be really nice if I could avoind that.

EDIT: What I'm currently using to store the data for the tiles is a 2D array of HashMaps that use the layer as key and store the id of the tile in that position - like this: private HashMap< Integer, Integer >[][]