Added class hierarchies.

double-dispatch/src/main/java/com/iluwatar/Meteoroid.java

@@ -0,0 +1,8 @@
+package com.iluwatar;
+
+public class Meteoroid extends GameObject {
+
+	public Meteoroid(int left, int top, int right, int bottom) {
+		super(left, top, right, bottom);
+	}
+}