public class GenericArrayStack<E> implements Stack<E> {

    // E is the type of the elements of this stack.  The specific type
    // will specified when a reference is declared and a stack is
    // actually created. E.g.:
    //
    // Stack<Integer> nums;
    // nums = new GenericArrayStack<Integer>( 10 );

    // Instance variables

    private E[] elems; // Used to store the elements of this ArrayStack
    private int top; // Designates the first free cell
    
    @SuppressWarnings( "unchecked" )

    // Constructor
    public GenericArrayStack( int capacity ) {
	elems = (E[]) new Object[ capacity ];
	// elems = new E[ capacity ];
	top = 0;
    }

    // Returns true if this ArrayStack is empty
    public boolean isEmpty() {
	return top == 0;
    }

    public void push( E elem ) {
	// pre-condition: ! isFull()

	elems[ top ] = elem;
	top++;

	
    }
    public E pop() {
	// pre-condition: ! isEmpty()

	E saved;

	top--;
	saved = elems[ top ];
	elems[ top ] = null;

	return saved;
    }

    public E peek() {
	// pre-condition: ! isEmpty()

	return elems[ top-1 ];
    }
}