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BEGIN LICENSE BLOCK ***** Version: EPL 1.0/GPL 2.0/LGPL 2.1 The contents of this file are subject to the Eclipse Public License Version 1.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at Software distributed under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the specific language governing rights and limitations under the License. Copyright (C) 2002-2004 Jan Arne Petersen <> Copyright (C) 2002-2004 Anders Bengtsson <> Copyright (C) 2004-2006 Charles O Nutter <> Copyright (C) 2004 Stefan Matthias Aust <> Alternatively, the contents of this file may be used under the terms of either of the GNU General Public License Version 2 or later (the "GPL"), or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which case the provisions of the GPL or the LGPL are applicable instead of those above. If you wish to allow use of your version of this file only under the terms of either the GPL or the LGPL, and not to allow others to use your version of this file under the terms of the EPL, indicate your decision by deleting the provisions above and replace them with the notice and other provisions required by the GPL or the LGPL. If you do not delete the provisions above, a recipient may use your version of this file under the terms of any one of the EPL, the GPL or the LGPL. END LICENSE BLOCK ***
package org.jruby.util.collections;
A Map that holds its values weakly and uses object identity for keys.
public class WeakValuedIdentityMap<Key, Value> {
    private final ReferenceQueue deadReferences = new ReferenceQueue();
    private final Map<Key, KeyedReference<Key, Value>> references = new IdentityHashMap<Key, KeyedReference<Key, Value>>();
    public synchronized void put(Key key, Value value) {
        .put(keynew KeyedReference(valuekey));
    public synchronized Value get(Key key) {
        KeyedReference<Key, Value> reference = .get(key);
        if (reference == null) {
            return null;
        return reference.get();
    private void cleanReferences() {
        KeyedReference ref;
        while ((ref = (KeyedReference.poll()) != null) {
    private static class KeyedReference<Key, Value> extends WeakReference<Value> {
        private final Key key;
        public KeyedReference(Value object, Key keyReferenceQueue queue) {
            this. = key;
        public Key key() {
            return ;
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