I am just watching this tutorial https://www.youtube.com/watch?v=HwUnMy_pR6A and the guy (who seems to be pretty competent) is using a single array to store and access the pixels of his to-be-rendered image. 

I was wondering if this really is the best way to do this. The alternative of Multi-Array does have one pointer more, but Arrays do have an O(1) for accessing each index and calculating the index in a single array seems to take one addition and one multiplication operation per pixel.

And if Multi-Arrays really are bad, can't you use something with Hashing to avoid those addition and multiplication operations?

EDIT: here is his code...

    public class Screen {
	private int width, height;
	public int[] pixels;

	public Screen(int width, int height) {
		this.width = width;
		this.height = height;

		// creating array the size of one index/int for every pixel
		// single array has better performance than multi-array
		pixels = new int[width * height];
	}

	public void render() {
		for (int y = 0; y < height; y++) {
			for (int x = 0; x < width; x++) {
				pixels[x + y * width] = 0xff00ff;
			}
		}
	}
    }