001    /*
002     * Copyright (C) 2007 Google Inc.
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005     * in compliance with the License. You may obtain a copy of the License at
006     *
007     * http://www.apache.org/licenses/LICENSE-2.0
008     *
009     * Unless required by applicable law or agreed to in writing, software distributed under the License
010     * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011     * or implied. See the License for the specific language governing permissions and limitations under
012     * the License.
013     */
014    
015    package com.google.common.base;
016    
017    import java.lang.ref.PhantomReference;
018    import java.lang.ref.ReferenceQueue;
019    
020    /**
021     * Phantom reference with a {@code finalizeReferent()} method which a background thread invokes
022     * after the garbage collector reclaims the referent. This is a simpler alternative to using a
023     * {@link ReferenceQueue}.
024     *
025     * <p>Unlike a normal phantom reference, this reference will be cleared automatically.
026     *
027     * @author Bob Lee
028     * @since 2 (imported from Google Collections Library)
029     */
030    public abstract class FinalizablePhantomReference<T> extends PhantomReference<T>
031        implements FinalizableReference {
032      /**
033       * Constructs a new finalizable phantom reference.
034       *
035       * @param referent to phantom reference
036       * @param queue that should finalize the referent
037       */
038      protected FinalizablePhantomReference(T referent, FinalizableReferenceQueue queue) {
039        super(referent, queue.queue);
040        queue.cleanUp();
041      }
042    }