CSC236 Data Structures - ArrayBoundedStack

ArrayBoundedStack

//----------------------------------------------------------------
// ArrayBoundedStack.java    by Dale/Joyce/Weems         Chapter 2
//
// Implements StackInterface using an array to hold the
// stack elements.
//
// Two constructors are provided: one that creates an array of a
// default size and one that allows the calling program to
// specify the size.
//----------------------------------------------------------------

public class ArrayBoundedStack<T> implements StackInterface<T> {
   protected final int DEFCAP = 100; // default capacity
   protected T[] elements;           // holds stack elements
   protected int topIndex = -1;      // index of top element in stack

   public ArrayBoundedStack() {
      elements = (T[]) new Object[DEFCAP];
   }

   public ArrayBoundedStack(int maxSize) {
      elements = (T[]) new Object[maxSize];
   }

   public void push(T element) {
   // Throws StackOverflowException if this stack is full,
   // otherwise places element at the top of this stack.
      if (isFull())
         throw new StackOverflowException("Push attempted on a full stack.");
      else {
         topIndex++;
         elements[topIndex] = element;
      }
   }

   public void pop() {
   // Throws StackUnderflowException if this stack is empty,
   // otherwise removes top element from this stack.
      if (isEmpty())
         throw new StackUnderflowException("Pop attempted on an empty stack.");
      else {
         elements[topIndex] = null;
         topIndex--;
      }
   }

   public T top() {
   // Throws StackUnderflowException if this stack is empty,
   // otherwise returns top element of this stack.
      T topOfStack = null;
      if (isEmpty())
         throw new StackUnderflowException("Top attempted on an empty stack.");
      else
         topOfStack = elements[topIndex];
      return topOfStack;
   }

   public boolean isEmpty() {
   // Returns true if this stack is empty, otherwise returns false.
      return (topIndex == -1);
   }

   public boolean isFull() {
   // Returns true if this stack is full, otherwise returns false.
      return (topIndex == (elements.length - 1));
   }
}