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.PhantomReference;
020import java.lang.ref.ReferenceQueue;
021
022/**
023 * Phantom reference with a {@code finalizeReferent()} method which a background thread invokes
024 * after the garbage collector reclaims the referent. This is a simpler alternative to using a
025 * {@link ReferenceQueue}.
026 *
027 * <p>Unlike a normal phantom reference, this reference will be cleared automatically.
028 *
029 * @author Bob Lee
030 * @since 2.0
031 */
032public abstract class FinalizablePhantomReference<T> extends PhantomReference<T>
033    implements FinalizableReference {
034  /**
035   * Constructs a new finalizable phantom reference.
036   *
037   * @param referent to phantom reference
038   * @param queue that should finalize the referent
039   */
040  protected FinalizablePhantomReference(T referent, FinalizableReferenceQueue queue) {
041    super(referent, queue.queue);
042    queue.cleanUp();
043  }
044}