Note: even if you had trouble completing question 1486 on string stacks, you could still attempt this question by starting with sample solution for question 1486.
Replace the StringStack interface of question 1486, with an interface GenericStack
that can hold elements of any given type, not necessarily String.
Replace the implementing classes StringStackArray and StringStackList with generic classes
GenericStackArray and GenericStackList that mimic the original classes, but store elements
of an arbitrary type rather than strings.
This should be fairly straightforward, with one exception: in the constructor of StringStackArray you probably created
a new array of strings:
elements = new String[STACK_LIMIT];
You would think (hope!) that the corresponding generic code would be:
elements = new E[STACK_LIMIT];
where E is the generic type parameter. However, this does not work. Why?
See below for a hint on how to solve this issue. (Also look at the source code given as part of question 96df.)
Write a Demo class with a static method, transferStacks.
However, this time transferStacks should be generic: given two generic stacks with the same type
parameter, it should transfer the contents of one to the other.
Write a main method that creates several stacks using different types (e.g., String,
PrintStream, or types from classes you have created yourself) and the two different representations
(GenericStackArray and GenericStackList). Dem-onstrate that your stacks are working
by transferring contents between stacks, and showing the contents of a stack by popping its elements one
by one and displaying them.
Hint: You cannot create a new array with generic element type E, but you
can create a new array with element type Object and cast it to an array with element type E. The compiler will
complain that this cast is unchecked, and in general such a cast is not safe, but clearly it will work here because the new array is
empty. You can shut the compiler up by adding the annotation:
@SuppressWarnings("unchecked")
to the constructor of GenericStackArray.