/**
   An interface for the ADT stack.
   @author Frank M. Carrano
   @author Timothy M. Henry
   @version 5.0
*/
public interface StackInterface<T>
{
   /** Adds a new entry to the top of this stack.
       @param newEntry  An object to be added to the stack. */
   public void push(T newEntry);
  
   /** Removes and returns this stack's top entry.
       @return  The object at the top of the stack. 
       @throws  EmptyStackException if the stack is empty before the operation. */
   public T pop();
  
   /** Retrieves this stack's top entry.
       @return  The object at the top of the stack.
       @throws  EmptyStackException if the stack is empty. */
   public T peek();
  
   /** Detects whether this stack is empty.
       @return  True if the stack is empty. */
   public boolean isEmpty();
  
   /** Removes all entries from this stack. */
   public void clear();
} // end StackInterface