/* Copyright (C) 2004 - 2007 db4objects Inc. http://www.db4o.com
This file is part of the db4o open source object database.
db4o is free software; you can redistribute it and/or modify it under
the terms of version 2 of the GNU General Public License as published
by the Free Software Foundation and as clarified by db4objects' GPL
interpretation policy, available at
http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
Suite 350, San Mateo, CA 94403, USA.
db4o 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
for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
package com.db4o.foundation;
/**
* @exclude
*/
public class Stack4 {
private List4 _tail;
public void push(Object obj) {
_tail = new List4(_tail, obj);
}
public Object peek() {
if(_tail == null){
return null;
}
return _tail._element;
}
public Object pop() {
if(_tail == null){
throw new IllegalStateException();
}
Object res = _tail._element;
_tail = _tail._next;
return res;
}
public boolean isEmpty() {
return _tail==null;
}
}
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