ArrayStack<E> a generic stack

The ArrayStack is an implementation of a stack of a generic type,
using an array of Objects. Objects are used because java does not
allow the creation of an array of a parameterised type.

NOTE:
  - The ArrayStack is visually reversed with respect to the NodeStack
  - What are implication of pop with respect to garbage collection (gc)?
  - Can we make ArrayStack "greener"?

The program Test.java allows us to play with a stack, of size 10, of String.
We keep it small so we can generate stack overflow, underflow, and empty exceptions

It would be nice to modify Test to give IntTest, using the ArrayStack<Integer>

NOTE: this code corresponds to Goodrich & Tamassia (4th ed) Chapter 5, pages 194 and 195

Patrick Prosser
14/01/2011