Question

Hello and thank you for reading this. I am coding in java/LWJGL. My problem is that I keep getting a null pointer error with some code if I don’t include this one thing. Basically there are 4 classes

• A block class.
• A blockGrid class
• A blocktype class
• And a boot class.

The boot class creates a display and in the game loop it runs the draw method that is inside the blockgrid class. To set where a block goes i would use the renderat(x,y) method inside the blockgrid method. The block class just creates a quad at a certain x,y.

Sorry if I’m not explaining good. Here is my code: This is where the error happens just read my comments to see where the error is.

// BlockGrid.java
package minecraft2d;

import java.io.File;

public class BlockGrid {
    private Block[][] blocks = new Block[100][100];

    public BlockGrid() {
        for (int x = 0; x < 25 - 1; x++) {
            for (int y = 0; y < 16 - 1; y++) {
                blocks[x][y] = new Block(BlockType.AIR, -100, -100); //This is where my error happens! If I don't include this line i get a null pointer. Anything will help. I am really stuck and don't know whats happening
            }
        }
    }
    public void setAt(int x, int y, BlockType b) {
        blocks[x][y] = new Block(b, x * 32, y * 32);
    }

    public void draw() {
        for (int x = 0; x < 25 - 1; x++) {
            for (int y = 0; y < 16 - 1; y++) {
                blocks[x][y].draw();
            }
        }
    }
}

Answer 1

The reason you get a NullPointerException when you don’t have that line is that blocks[x][y] will be null for all x,y when draw() is called. draw() assumes you have valid Block objects because it’s calling Block#draw.