public class ArrayStack<E> implements StackADT<E> {


  // field to refer to an array which will hold the stack elements

  protected E[] S;

  // index to top element

  protected int top = -1;



  // a constructor

  public ArrayStack(int cap) {

     S = (E[]) new Object[cap];

  // compiler may give warning, but this
  // is OK

  }

  public ArrayStack() {

	     S = (E[]) new Object[10];
  }




  public int size () {

     return (top +1);

  }



  public boolean isEmpty() {

     return (top <0);

  }



  public E pop() throws EmptyStackException  {

     E element;

     if (isEmpty())

        throw new EmptyStackException("Empty stack: cannot pop");

     element = S[top];

     S[top] = null; // facilitates garbage collection

     top = top - 1;

     return element;

  }



  public E top() throws EmptyStackException {

     if (isEmpty())

       throw new EmptyStackException("Stack is empty. Cannot obtain an element");

     return S[top];

  }



  public void push(E element){

	     // include method body
	if (size() == top) {
	    E[] ProvS = (E[]) new Object[S.length*2];

	    for (int i= 0; i<S.length; i++) {
	        ProvS[i] = S[i];
	    }
	        S = ProvS;
	        ProvS = null;
	  }
	  top++;
	  S[top]=element;

	}
	  }