Resizing a 2D array of objects

Game Mechanics
#1

Hi

For my game’s map system I have a 2D array of [icode]Block[/icode] objects. I would like to resize/trim the array of null/empty rows and columns. Here is my current code, which doesn’t work :confused:


   Block[][] clone = worldBlocks.clone();
		int maxX = 0, maxY = 0;
		for(Block[] row : clone){
			if(row != null){
				maxX = 0;
				for(Block block : row){
					if(block != null){
						maxX++;
					}
				}
				maxY++;
			}
		}
		Block[][] refreshed = new Block[maxY][maxX];
		for(int y = 0; y < maxY; y++){
			for(int x = 0; x < maxX; x++){
				refreshed[y][x] = clone[y][x];
			}
		}
		worldBlocks = refreshed.clone();

This code should remove any null rows and columns, but it doesn’t :slight_smile: Any thoughts or fixes would be appreciated :slight_smile:

CopyableCougar4

#2

refreshed[ y ][ x ] = clone[ y ][ x ];

I think this is where your issues is, you are not ‘skipping’ your initial blank positions.

I will try and give you an example,

You have a single dimension array of 1s, 0s.

Like {0,0,1,1,0,0,1}

What you work out in your code is the number of 1s. So 3 in this example, then what you are currently doing is getting the first 3 entries in your code. So you will end up with,

{0,0,1}. Which is not what you seem to want.

#3

Hi

I should probably explain more.

I create an array 10x10 just so that I won’t run out of room, and then I want to shrink it so that there are no empty elements. Initially the array looks like this:


1 1 1 1 0 0 0 0 0 0 0 0 0 0
1 1 1 1 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0

But I want it to be like this:


1 1 1 1
1 1 1 1

Hope this makes it more clear :slight_smile:

CopyableCougar4

#4

I have a feeling you’re doing something kinda hacky elsewhere if this is how you’re setting up your block objects.

But, you can try this hacky code here:

byte [][] oldArray = new byte[10][10]
int rows = 0;
int col = 0;

for (int x = 0; x < oldArray.length; x++) {
	for (int y = 0; y < oldArray[x].length; y++) {
		if (oldArray[x][y] == 1){
			row = x;
			col = y;
		}
	}
}

byte[][] newArray = new byte[row][col];
for (int x = 0; x < newArray[].length; x++) {
	Arrays.fill(newArray[], 1);
}

Totally untested code (and really hacky, you shouldn’t really be doing this at all), but in theory it’ll output a new array full of 1s, in the new size. Keep in mind it will only work for rectangle shapes.

#5

Do you want to trim the array, or remove all nulls?

#6

Hi

This is how I read in my map data:


   public WorldReader(File file){
		ArrayList<String> lines = readFileToList(file);
@@		world = new World(10, 10); // Allocate space for 100 blocks
		int y = 0, x = 0;
		Block activeBlock = null;
		int blockX = -1, blockY = -1, width = -1, height = -1;
		Tile[][] tilemap = null;
		loop:
		for(String line : lines){
			if(line.startsWith("-------")){
				if(activeBlock != null){
					activeBlock.setTilemap(tilemap);
					world.setBlock(blockX, blockY, activeBlock);
					activeBlock = null;
				}
				String blockInfo = line.substring(7, line.length());
				if(blockInfo.length() <= 0){
					break loop;
				}
				String[] blockData = blockInfo.split(",");
				String blockName = blockData[0];
				blockX = Integer.parseInt(blockData[1]);
				blockY = Integer.parseInt(blockData[2]);
				width = Integer.parseInt(blockData[3]);
				height = Integer.parseInt(blockData[4]);
				tilemap = new Tile[height][width];
				activeBlock = new Block(blockName);
				continue loop;
			}
			x = 0;
			for(String statement : line.split(" ")){
				String layer1 = statement.substring(0, 1);
				int tileID = Integer.parseInt(layer1);
				Tile tile = TileRegistry.getMap().get(tileID);
				tilemap[y][x] = tile;
				x++;
			}
			y++;
		}
@@		world.trim(); // Trim null rows and columns
		System.out.println(world.getWidth() + "x" + world.getHeight());
	}

This is why I have to have hacky world code, because I don’t know how big the array will be until AFTER the whole file has been read/parsed.

CopyableCougar4

#7

Simple: change your file format to include a header row that tells you the dimensions, and walk away from all this hackiness.

#8

Hi

I suppose that would work :stuck_out_tongue:

CopyableCougar4

#9

That, or even use a List<List> as you parse, and use toArray() when done filling it with blocks.

#10

Hi

So I added that one line about the block dimensions and it solved my problem :slight_smile: Why do the easiest solutions evade me so often? :slight_smile:

CopyableCougar4