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   * 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     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;
  }
  