Question

I am attempting to make an infinite world 2d game

source for the class is here:

package com.blazingkin.world;
import java.util.LinkedList;
import java.util.List;

import com.blazingkin.atrox.AtroxAdventrum;

public class World {

    public World(AtroxAdventrum aa){
        chunks = new LinkedList<List<Chunk>>();
    }

    public void setBlock(int x, int y, int newBlock){

    }

    public void setMetadata(int x, int y, int newMeta){

    }
    public int getBlock(int x, int y){
        try{
            Chunk c = chunks.get(x/64 - x%64).get(y/64 - y%64);
            return c.chunk[x%64][y%64];
        }
        catch(Exception e){
            try{
            Chunk c = new Chunk(y, x/64 - x%64, y/64 - y%64);
            chunks.get(x/64 - x%64).add(y/64 - y%64 - 1, c);
            return c.chunk[x%64][y%64]; 
        }catch(Exception e1){
            Chunk c = new Chunk(y, x/64 - x%64, y/64 - y%64);
            List<Chunk> newlist = new LinkedList<Chunk>();
            System.out.println(""+x+", "+y);
            for (int i = 0; i<y/64 - y%64; i++){
                newlist.add(i, new Chunk(y - (y/64 - y%64 - i), x/64 - x%64, y/64 - y%64 - (y/64 - y%64 - i)));
            }
            newlist.add(y/64 - y%64 - 1, c);
            for (int i = 0; i<x/64 - x%64; i++){
                newlist.add(i, new Chunk(x - (x/64 - x%64 - i), x/64 - x%64, x/64 - x%64 - (x/64 - x%64 - i)));
            }
            chunks.add(x/64 - 1 - x%64, null);

            return 0;
        }
        }




    }
    public int getMetadata(int x, int y){
        return 1;
    }



    public List<List<Chunk>> chunks;

}

However, when i attempt to run this code i get the following error:

Exception in thread “main” java.lang.IndexOutOfBoundsException: Index: 23, Size: 0
at java.util.LinkedList.entry(Unknown Source)
at java.util.LinkedList.add(Unknown Source)
at com.blazingkin.world.World.getBlock(World.java:41)
at com.blazingkin.render.ScreenOutput.render(ScreenOutput.java:30)
at com.blazingkin.atrox.AtroxAdventrum.draw(AtroxAdventrum.java:34)
at com.blazingkin.atrox.Core.gameLoop(Core.java:60)
at com.blazingkin.atrox.Core.run(Core.java:27)
at com.blazingkin.atrox.AtroxAdventrum.main(AtroxAdventrum.java:14)

Any suggestions as to how i could fix this?

Answer 1

A LinkedList is not a good choice for what you are trying to do. First, attempting to access elements of LinkedList by index is bad (performs O(n) instead of O(1)).

Use:

Map<Integer,Map<Integer,Chunk>> chunks = new HashMap<Integer,Map<Integer,Chunk>>();

private void setChunk(Integer x, Integer y, Chunk c) {
    if(chunks.get(x) == null) {
        chunks.put(x, new HashMap<Integer, Chunk>());
    }
    chunks.get(x).put(y, c);
}
private Chunk getChunk(Integer x, Integer y) {
    if(chunks.get(x) == null)
        return null;
    return chunks.get(x).get(y);
}

In your code, you can use setChunk(1238238, -12938123, new Chunk(…)) and it will key the chunk under the x and y coordinate. To retrieve the value, use getChunk(1238238, -12938123). If no chunk exists for a given x, y, null will be returned.