PPT Slide
1. If class C1 extends class C2 then C1 is a subtype of C2.
2. If interface I1 extends interface I2 then I is a subtype of I2.
3. If class C implements interface I then C is a subtype of I.
4. For every interface I, I is a subtype of Object.
5. For every type T, refernce or primitive type, T[] (array of type T) is a
6. If type T1 is a subtype of T2 then T1 is a subtype of T2 [].