/**
 * Base interface for stack implementations, uses generics.  
 */
public interface Stack<E> {
	/**
	 * Returns true if stack has no elements
	 *
	 * @return 	true if the stack has no elements
	 */
	public boolean isEmpty();


	/**
	 * Get the most recently inserted item in the stack.
	 * Does not alter the stack.
	 *
	 * @return the most recently inserted item in the stack.
	 * @exception UnderflowException	Thrown if stack is empty.
	 */
	public E top();


	/**
	 * Remove the most recently inserted item from the stack.
	 *
	 * @exception UnderflowException	Thrown if stack is empty.
	 */
	public void pop();



	/**
	 * Insert a new item into the stack, if not already full.
	 *
	 * @param x the item to insert.
	 */
	public void push( E x );


	/**
	 * Erases all elements from the stack.
	 */
	public void makeEmpty();

}