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95 lines
2.9 KiB
Java
95 lines
2.9 KiB
Java
/**
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*
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* Copyright the original author or authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.jivesoftware.smack.util;
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import java.lang.ref.WeakReference;
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import java.util.HashMap;
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import java.util.Iterator;
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/**
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* Extends a {@link HashMap} with {@link WeakReference} values, so that
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* weak references which have been cleared are periodically removed from
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* the map. The cleaning occurs as part of {@link #put}, after a specific
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* number ({@link #cleanInterval}) of calls to {@link #put}.
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*
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* @param <K> The key type.
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* @param <V> The value type.
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*
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* @author Boris Grozev
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*/
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public class CleaningWeakReferenceMap<K, V>
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extends HashMap<K, WeakReference<V>> {
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private static final long serialVersionUID = 0L;
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/**
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* The number of calls to {@link #put} after which to clean this map
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* (i.e. remove cleared {@link WeakReference}s from it).
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*/
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private final int cleanInterval;
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/**
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* The number of times {@link #put} has been called on this instance
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* since the last time it was {@link #clean}ed.
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*/
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private int numberOfInsertsSinceLastClean = 0;
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/**
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* Initializes a new {@link CleaningWeakReferenceMap} instance with the
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* default clean interval.
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*/
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public CleaningWeakReferenceMap() {
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this(50);
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}
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/**
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* Initializes a new {@link CleaningWeakReferenceMap} instance with a given
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* clean interval.
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* @param cleanInterval the number of calls to {@link #put} after which the
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* map will clean itself.
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*/
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public CleaningWeakReferenceMap(int cleanInterval) {
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this.cleanInterval = cleanInterval;
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}
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@Override
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public WeakReference<V> put(K key, WeakReference<V> value) {
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WeakReference<V> ret = super.put(key, value);
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if (numberOfInsertsSinceLastClean++ > cleanInterval) {
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numberOfInsertsSinceLastClean = 0;
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clean();
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}
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return ret;
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}
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/**
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* Removes all cleared entries from this map (i.e. entries whose value
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* is a cleared {@link WeakReference}).
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*/
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private void clean() {
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Iterator<Entry<K, WeakReference<V>>> iter = entrySet().iterator();
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while (iter.hasNext()) {
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Entry<K, WeakReference<V>> e = iter.next();
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if (e != null && e.getValue() != null
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&& e.getValue().get() == null) {
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iter.remove();
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}
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}
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}
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}
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