/*

  * Copyright (c) 1994, 2010, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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  */

 package java.util;

 /**

  * The <code>Stack</code> class represents a last-in-first-out

  * (LIFO) stack of objects. It extends class <tt>Vector</tt> with five

  * operations that allow a vector to be treated as a stack. The usual

  * <tt>push</tt> and <tt>pop</tt> operations are provided, as well as a

  * method to <tt>peek</tt> at the top item on the stack, a method to test

  * for whether the stack is <tt>empty</tt>, and a method to <tt>search</tt>

  * the stack for an item and discover how far it is from the top.

  * <p>

  * When a stack is first created, it contains no items.

  *

  * <p>A more complete and consistent set of LIFO stack operations is

  * provided by the {@link Deque} interface and its implementations, which

  * should be used in preference to this class.  For example:

  * <pre>   {@code

  *   Deque<Integer> stack = new ArrayDeque<Integer>();}</pre>

  *

  * @author  Jonathan Payne

  * @since   JDK1.0

  */

 public

 class Stack<E> extends Vector<E> {

     /**

      * Creates an empty Stack.

      */

     public Stack() {

     }

     /**

      * Pushes an item onto the top of this stack. This has exactly

      * the same effect as:

      * <blockquote><pre>

      * addElement(item)</pre></blockquote>

      *

      * @param   item   the item to be pushed onto this stack.

      * @return  the <code>item</code> argument.

      * @see     java.util.Vector#addElement

      */

     public E push(E item) {

         addElement(item);

         return item;

     }

     /**

      * Removes the object at the top of this stack and returns that

      * object as the value of this function.

      *

      * @return  The object at the top of this stack (the last item

      *          of the <tt>Vector</tt> object).

      * @throws  EmptyStackException  if this stack is empty.

      */

     public synchronized E pop() {

         E       obj;

         int     len = size();

         obj = peek();

         removeElementAt(len - 1);

         return obj;

     }

     /**

      * Looks at the object at the top of this stack without removing it

      * from the stack.

      *

      * @return  the object at the top of this stack (the last item

      *          of the <tt>Vector</tt> object).

      * @throws  EmptyStackException  if this stack is empty.

      */

     public synchronized E peek() {

         int     len = size();

         if (len == 0)

             throw new EmptyStackException();

         return elementAt(len - 1);

     }

     /**

      * Tests if this stack is empty.

      *

      * @return  <code>true</code> if and only if this stack contains

      *          no items; <code>false</code> otherwise.

      */

     public boolean empty() {

         return size() == 0;

     }

     /**

      * Returns the 1-based position where an object is on this stack.

      * If the object <tt>o</tt> occurs as an item in this stack, this

      * method returns the distance from the top of the stack of the

      * occurrence nearest the top of the stack; the topmost item on the

      * stack is considered to be at distance <tt>1</tt>. The <tt>equals</tt>

      * method is used to compare <tt>o</tt> to the

      * items in this stack.

      *

      * @param   o   the desired object.

      * @return  the 1-based position from the top of the stack where

      *          the object is located; the return value <code>-1</code>

      *          indicates that the object is not on the stack.

      */

     public synchronized int search(Object o) {

         int i = lastIndexOf(o);

         if (i >= 0) {

             return size() - i;

         }

         return -1;

     }

     /** use serialVersionUID from JDK 1.0.2 for interoperability */

     private static final long serialVersionUID = 1224463164541339165L;

 }