Krazee soul

Can somebody tell me how command and strategy patterns differ?when to prefer one over other?

rgds
krazee soul

Yes that is what I mean

What are the differences between a pure abstract class & interface apart from the fact that interfaces allow multiple inheritance?

so what do they really mean by superclass constructor is invoked?Does that not mean superclass object is created?An object at depth three in inheritance tree will need three objects created and at depth six will need
six objects created?

A constructor calls its parent class constructor and thus for every object creation constructor of class Object is called.
Does this mean a class lower in inheritance tree has more memory overhead?