Search:

I suggest you go back to the books for a while. There's so much wrong in your code. I have no idea whether you're trying to create an applet or a Swing application, all the stuff is static,...

You call paint with null as the first parameter. This cannot work.

public static void createTiles(int X, int Y, int Height, int Width) {
client.paint(null, X, Y, Height, Width);
}
client is null. You've never instanciated it, but I don't see why you need that...