package DataStructures;

/**
 * A last-in-first-out (LIFO) stack of objects.
 * @author Peter Williams
 */

public interface Stack {
    /**
     * Indicates the status of the stack.
     * @return <code>true</code> if the stack is empty.
     */
    public boolean isEmpty();

    /**
     * Pushes an item onto the stack.
     * @param <code>item</code> the Object to be pushed.
     */
    public void push(Object item);
  
    /**
     * Pops an item off the stack.
     * @return the item most recently pushed onto the stack
     * @exception NoSuchElementException if the stack is empty.
     */
    public Object pop();
}