001/*
002 * Copyright (C) 2007 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.base;
018
019import java.lang.ref.ReferenceQueue;
020import java.lang.ref.WeakReference;
021
022/**
023 * Weak reference with a {@code finalizeReferent()} method which a background thread invokes after
024 * the garbage collector reclaims the referent. This is a simpler alternative to using a {@link
025 * ReferenceQueue}.
026 *
027 * @author Bob Lee
028 * @since 2.0
029 */
030public abstract class FinalizableWeakReference<T> extends WeakReference<T>
031    implements FinalizableReference {
032  /**
033   * Constructs a new finalizable weak reference.
034   *
035   * @param referent to weakly reference
036   * @param queue that should finalize the referent
037   */
038  protected FinalizableWeakReference(T referent, FinalizableReferenceQueue queue) {
039    super(referent, queue.queue);
040    queue.cleanUp();
041  }
042}