1   /*
2    * Copyright (C) 2011 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.cache;
18  
19  import static com.google.common.base.Preconditions.checkNotNull;
20  
21  import com.google.common.annotations.Beta;
22  
23  import java.util.concurrent.Executor;
24  
25  /**
26   * A collection of common removal listeners.
27   *
28   * @author Charles Fry
29   * @since 10.0
30   */
31  @Beta
32  public final class RemovalListeners {
33  
34    private RemovalListeners() {}
35  
36    /**
37     * Returns a {@code RemovalListener} which processes all eviction
38     * notifications using {@code executor}.
39     *
40     * @param listener the backing listener
41     * @param executor the executor with which removal notifications are
42     *     asynchronously executed
43     */
44    public static <K, V> RemovalListener<K, V> asynchronous(
45        final RemovalListener<K, V> listener, final Executor executor) {
46      checkNotNull(listener);
47      checkNotNull(executor);
48      return new RemovalListener<K, V>() {
49        @Override
50        public void onRemoval(final RemovalNotification<K, V> notification) {
51          executor.execute(new Runnable() {
52            @Override
53            public void run() {
54              listener.onRemoval(notification);
55            }
56          });
57        }
58      };
59    }
60  
61  }