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package com.c2kernel.utils;
import java.lang.ref.*;
import java.util.*;
/**************************************************************************
* TransientCache - Uses transient references to allow unused entries to be
* reaped by the java garbage collector.
*
* $Revision: 1.1 $
* $Date: 2004/04/20 09:37:02 $
*
* Copyright (C) 2003 CERN - European Organization for Nuclear Research
* All rights reserved.
**************************************************************************/
public abstract class TransientCache extends AbstractMap {
private Map map = new Hashtable();
public synchronized Set entrySet() {
Map newMap;
Iterator iter;
newMap = new Hashtable();
iter = map.entrySet().iterator();
while (iter.hasNext()) {
Map.Entry me = (Map.Entry)iter.next();
Reference ref = (Reference)me.getValue();
Object o = ref.get();
if (o == null) {
// Delete cleared reference
iter.remove();
} else {
// Copy out interior object
newMap.put(me.getKey(), o);
}
}
// Return set of interior objects
return newMap.entrySet();
}
public synchronized Object put(Object key, Object value) {
Reference ref = makeReference(value);
ref = (Reference)map.put(key, ref);
if (ref != null)
return (ref.get());
return null;
}
public abstract Reference makeReference(Object value);
public Object remove(Object key) {
Iterator i = map.entrySet().iterator();
Entry correctEntry = null;
if (key == null) {
while (correctEntry == null && i.hasNext()) {
Entry e = (Entry)i.next();
if (e.getKey() == null)
correctEntry = e;
}
} else {
while (correctEntry == null && i.hasNext()) {
Entry e = (Entry)i.next();
if (key.equals(e.getKey()))
correctEntry = e;
}
}
Object oldValue = null;
if (correctEntry != null) {
Reference correctReference = (Reference)correctEntry.getValue();
oldValue = correctReference.get();
i.remove();
}
return oldValue;
}
/**
*
*/
public void clear() {
map.entrySet().clear();
}
private transient Set keySet = null;
public Set keySet() {
if (keySet == null) {
keySet = new AbstractSet() {
public Iterator iterator() {
return new Iterator() {
private Iterator i = map.entrySet().iterator();
public boolean hasNext() {
return i.hasNext();
}
public Object next() {
return ((Entry)i.next()).getKey();
}
public void remove() {
i.remove();
}
};
}
public int size() {
return TransientCache.this.size();
}
public boolean contains(Object k) {
return TransientCache.this.containsKey(k);
}
};
}
return keySet;
}
}
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