657 B
657 B
Composition (#2)
The starter code contains implementations of Stack and Queue classes.
Stack provides last-in-first-out access to elements. You can add ("push")
new elements, and get ("pop") the last element that was added.
Queue provides first-in-first-out access to elements. You can add new
elements to it, and get ("poll") returns the first element that was added.
In the starter code, both Stack and Queue extend ArrayList, which opens
too many methods in the public API (for example, you can get the first element
in Stack, which contradicts its design). Use composition instead of
inheritance to implement Stack and Queue.