Java double question.

Does anyone know why

public class Raytracer {
	private static int left = -4;
	private static int right = 4;
	private static int bottom = -3;
	private static int top = 3;
	private static int imageHeight = 600;
	private static int imageWidth = 800;
	private static int diffX = right - left;
	private static int diffY = top - bottom;
	private static double deltaX = diffX / imageWidth;
	private static double deltaY = diffY / imageHeight;

        public static void main(String args[]) {
                ...
        }
}

both deltaX and deltaY are always 0.0 when I evaluate this? It's driving me daft, I know there's a simple explanation but I can't see it. TIA