1   /*
2    * Copyright (C) 2007 The Guava Authors
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    * http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package com.google.common.base;
18  
19  import java.lang.ref.ReferenceQueue;
20  import java.lang.ref.SoftReference;
21  
22  /**
23   * Soft reference with a {@code finalizeReferent()} method which a background thread invokes after
24   * the garbage collector reclaims the referent. This is a simpler alternative to using a {@link
25   * ReferenceQueue}.
26   *
27   * @author Bob Lee
28   * @since 2.0 (imported from Google Collections Library)
29   */
30  public abstract class FinalizableSoftReference<T> extends SoftReference<T>
31      implements FinalizableReference {
32    /**
33     * Constructs a new finalizable soft reference.
34     *
35     * @param referent to softly reference
36     * @param queue that should finalize the referent
37     */
38    protected FinalizableSoftReference(T referent, FinalizableReferenceQueue queue) {
39      super(referent, queue.queue);
40      queue.cleanUp();
41    }
42  }