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// **********************************************************************
//
// Copyright (c) 2003
// ZeroC, Inc.
// Billerica, MA, USA
//
// All Rights Reserved.
//
// Ice is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License version 2 as published by
// the Free Software Foundation.
//
// **********************************************************************
package Freeze;
//
// Stripped down LinkedList implementation for use in the Evictor. The
// API is similar to java.util.LinkedList.
//
// Major differences:
// * listIterator() is not implemented.
// * Operation riterator() returns a reverse iterator.
// * This implementation also has the property that an Iterator can be
// retained over structural changes to the list itself (similar to an
// STL list).
//
class LinkedList
{
public
LinkedList()
{
_header.next = _header.previous = _header;
}
public Object
getFirst()
{
if(_size == 0)
{
throw new java.util.NoSuchElementException();
}
return _header.next.element;
}
public void
addFirst(Object o)
{
addBefore(o, _header.next);
}
public boolean
isEmpty()
{
return _size == 0;
}
public int
size()
{
return _size;
}
public java.util.Iterator
iterator()
{
return new ForwardIterator();
}
public java.util.Iterator
riterator()
{
return new ReverseIterator();
}
private class ForwardIterator implements java.util.Iterator
{
public boolean
hasNext()
{
return _next != null;
}
public Object
next()
{
if(_next == null)
{
throw new java.util.NoSuchElementException();
}
_current = _next;
if(_next.next != _header)
{
_next = _next.next;
}
else
{
_next = null;
}
return _current.element;
}
public void
remove()
{
if(_current == null)
{
throw new IllegalStateException();
}
LinkedList.this.remove(_current);
_current = null;
}
ForwardIterator()
{
if(_header.next == _header)
{
_next = null;
}
else
{
_next = _header.next;
}
_current = null;
}
private Entry _current;
private Entry _next;
}
private class ReverseIterator implements java.util.Iterator
{
public boolean
hasNext()
{
return _next != null;
}
public Object
next()
{
if(_next == null)
{
throw new java.util.NoSuchElementException();
}
_current = _next;
if(_next.previous != _header)
{
_next = _next.previous;
}
else
{
_next = null;
}
return _current.element;
}
public void
remove()
{
if(_current == null)
{
throw new IllegalStateException();
}
LinkedList.this.remove(_current);
_current = null;
}
ReverseIterator()
{
if(_header.next == _header)
{
_next = null;
}
else
{
_next = _header.previous;
}
_current = null;
}
private Entry _current;
private Entry _next;
}
private static class Entry
{
Object element;
Entry next;
Entry previous;
Entry(Object element, Entry next, Entry previous)
{
this.element = element;
this.next = next;
this.previous = previous;
}
}
private Entry
addBefore(Object o, Entry e)
{
Entry newEntry = new Entry(o, e, e.previous);
newEntry.previous.next = newEntry;
newEntry.next.previous = newEntry;
_size++;
return newEntry;
}
private void
remove(Entry e)
{
if(e == _header)
{
throw new java.util.NoSuchElementException();
}
e.previous.next = e.next;
e.next.previous = e.previous;
_size--;
}
private Entry _header = new Entry(null, null, null);
private int _size = 0;
}
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