Initialize/set a base class from a another base class instance

Question

Hi,
How can I initialize/set a base class from a another base class instance? I do not want to do a copy of it.
It would look something like:
class A {...}
class B extends A
    B(A a)
        // super = a;
    setA(A a)
        // super = a;
}Thank you.

Answer 1

erikku wrote:
Thanks Winton. It is what I did first but A has lots of methods and if methods are later added to A, I will have to edit B again. For those two reasons, I wanted to use inheritance. The part I was not sure with was the way to initialize B's base (A).You pays your money and you takes your choice. One way (this way) you have to provide forwarders; the other way (inheritance) you have to provide constructors (and if A has a lot of em, you may be writing quite a few).
Ask yourself this question: is every B also an A? No exceptions. Ever.
If the answer is 'yes', then inheritance is probably the best way to go.
However, if there is even the remotest chance that an instance of B should not exhibit 100% of the behaviour of A, now or in the future, then the wrapper style is probably what you want.
Another great advantage of the wrapper style is that methods can be added to A without affecting the API for B (unless you want to).
Winston
PS: If your Class A has a constructor or constructors that take a pile of parameters, you might also want to look at the Builder pattern. However, that's not really what we're talking about here, and it should probably be implemented on A anyway.