01: /*
02: * JBoss, Home of Professional Open Source.
03: * Copyright 2006, Red Hat Middleware LLC, and individual contributors
04: * as indicated by the @author tags. See the copyright.txt file in the
05: * distribution for a full listing of individual contributors.
06: *
07: * This is free software; you can redistribute it and/or modify it
08: * under the terms of the GNU Lesser General Public License as
09: * published by the Free Software Foundation; either version 2.1 of
10: * the License, or (at your option) any later version.
11: *
12: * This software is distributed in the hope that it will be useful,
13: * but WITHOUT ANY WARRANTY; without even the implied warranty of
14: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15: * Lesser General Public License for more details.
16: *
17: * You should have received a copy of the GNU Lesser General Public
18: * License along with this software; if not, write to the Free
19: * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20: * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21: */
22: package test.dbc.stack;
23:
24: import java.util.LinkedList;
25:
26: /**
27: *
28: * @author <a href="mailto:kabir.khan@jboss.org">Kabir Khan </a>
29: * @version $Revision: 57186 $
30: */
31: public class StackImpl implements Stack {
32: private final LinkedList elements = new LinkedList();
33:
34: public void push(Object o) {
35: elements.add(o);
36: }
37:
38: public Object pop() {
39: //For this we need $old functionality
40: //* @@org.jboss.aspects.dbc.PostCond ({"$tgt.top() == $rtn"})
41: final Object popped = top();
42: elements.removeLast();
43: return popped;
44: }
45:
46: public Object top() {
47: if (elements.size() == 0) {
48: return null;
49: }
50: return elements.getLast();
51: }
52:
53: public boolean isEmpty() {
54: return elements.size() == 0;
55: }
56: }
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