Stack


1   /*
2     Copyright (C) 2001 Laurent Martelli
3   
4     This program is free software; you can redistribute it and/or modify
5     it under the terms of the GNU Lesser General Public License as
6     published by the Free Software Foundation; either version 2 of the
7     License, or (at your option) any later version.
8   
9     This program is distributed in the hope that it will be useful,
10    but WITHOUT ANY WARRANTY; without even the implied warranty of
11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12    GNU Lesser General Public License for more details.
13  
14    You should have received a copy of the GNU Lesser General Public License
15    along with this program; if not, write to the Free Software
16    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
17  
18  package org.objectweb.jac.util;
19  
20  public class Stack extends java.util.Stack   {
21      /**
22       * Returns the i-th element from the top of the stack
23       *
24       * @param i index of element to get (0 is the top of the stack,
25       * size()-1 is the bottom)
26       *
27       * @see #poke(int,Object)
28       * @see #top()
29       */
30      public Object   peek(int i) {
31          return get(size()-1-i);
32      }
33  
34      /**
35       * Returns the top element of the stack
36       */
37      public Object   top() {
38          return peek(0);
39      }
40  
41      /**
42       * Returns the top element of the stack if it's not empty, null
43       * otherwise.
44       */
45      public Object   safeTop() {
46          return empty()?null:peek(0);
47      }
48  
49      /**
50       * Sets the value of an element of the stack
51       *
52       * @param i index of element to set (0 is the top of the stack,
53       * size()-1 is the bottom)
54       * @param value the new value
55       *
56       * @see #peek(int)
57       */
58      public void poke(int i, Object   value) {
59          set(size()-1-i,value);
60      }
61      /**
62      * Pops n elements from the top of the stack
63      * @param n number of elements to pop off the stack
64      */
65      public void pop(int n) {
66          for (;n>0; n--) {
67              pop();
68          }
69      }
70      /**
71      * swap peek() and peek(1)
72      */
73      public void swap() {
74          Object   tmp = peek();
75          poke(0,peek(1));
76          poke(1,tmp);
77      }
78  }
79
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