1 /*
2 * Copyright (C) 2011 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.cache;
16
17 import static com.google.common.base.Preconditions.checkNotNull;
18
19 import com.google.common.annotations.GwtCompatible;
20 import java.util.AbstractMap.SimpleImmutableEntry;
21 import org.checkerframework.checker.nullness.qual.Nullable;
22
23 /**
24 * A notification of the removal of a single entry. The key and/or value may be null if they were
25 * already garbage collected.
26 *
27 * <p>Like other {@code Entry} instances associated with {@code CacheBuilder}, this class holds
28 * strong references to the key and value, regardless of the type of references the cache may be
29 * using.
30 *
31 * @author Charles Fry
32 * @since 10.0
33 */
34 @GwtCompatible
35 public final class RemovalNotification<K, V> extends SimpleImmutableEntry<K, V> {
36 private final RemovalCause cause;
37
38 /**
39 * Creates a new {@code RemovalNotification} for the given {@code key}/{@code value} pair, with
40 * the given {@code cause} for the removal. The {@code key} and/or {@code value} may be {@code
41 * null} if they were already garbage collected.
42 *
43 * @since 19.0
44 */
45 public static <K, V> RemovalNotification<K, V> create(
46 @Nullable K key, @Nullable V value, RemovalCause cause) {
47 return new RemovalNotification(key, value, cause);
48 }
49
50 private RemovalNotification(@Nullable K key, @Nullable V value, RemovalCause cause) {
51 super(key, value);
52 this.cause = checkNotNull(cause);
53 }
54
55 /** Returns the cause for which the entry was removed. */
56 public RemovalCause getCause() {
57 return cause;
58 }
59
60 /**
61 * Returns {@code true} if there was an automatic removal due to eviction (the cause is neither
62 * {@link RemovalCause#EXPLICIT} nor {@link RemovalCause#REPLACED}).
63 */
64 public boolean wasEvicted() {
65 return cause.wasEvicted();
66 }
67
68 private static final long serialVersionUID = 0;
69 }