1 /*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15 package com.google.common.base;
16
17 import com.google.common.annotations.GwtIncompatible;
18 import java.lang.ref.PhantomReference;
19 import java.lang.ref.ReferenceQueue;
20 import javax.annotation.CheckForNull;
21
22 /**
23 * Phantom reference with a {@code finalizeReferent()} method which a background thread invokes
24 * after the garbage collector reclaims the referent. This is a simpler alternative to using a
25 * {@link ReferenceQueue}.
26 *
27 * <p>Unlike a normal phantom reference, this reference will be cleared automatically.
28 *
29 * @author Bob Lee
30 * @since 2.0
31 */
32 @GwtIncompatible
33 @ElementTypesAreNonnullByDefault
34 public abstract class FinalizablePhantomReference<T> extends PhantomReference<T>
35 implements FinalizableReference {
36 /**
37 * Constructs a new finalizable phantom reference.
38 *
39 * @param referent to phantom reference
40 * @param queue that should finalize the referent
41 */
42 protected FinalizablePhantomReference(@CheckForNull T referent, FinalizableReferenceQueue queue) {
43 super(referent, queue.queue);
44 queue.cleanUp();
45 }
46 }