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