pops a number of items from the stack (from bottom since it's a FIFO Stack)
If there aren't enoguh items in stack, all the items are poped, and the returned array's length is less than popCount
the elements poped
Exception if stack is empty
See Implementation
pops a number of items from the stack (from bottom since it's a FIFO Stack)
If there aren't enoguh items in stack, all the items are poped, and the returned array's length is less than popCount