001/*
002 * Copyright (C) 2011 The Guava Authors
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
015package com.google.common.cache;
016
017import static com.google.common.base.Preconditions.checkNotNull;
018
019import com.google.common.annotations.GwtCompatible;
020import java.util.AbstractMap.SimpleImmutableEntry;
021import javax.annotation.CheckForNull;
022import org.checkerframework.checker.nullness.qual.Nullable;
023
024/**
025 * A notification of the removal of a single entry. The key and/or value may be null if they were
026 * already garbage collected.
027 *
028 * <p>Like other {@code Entry} instances associated with {@code CacheBuilder}, this class holds
029 * strong references to the key and value, regardless of the type of references the cache may be
030 * using.
031 *
032 * @author Charles Fry
033 * @since 10.0
034 */
035@GwtCompatible
036public final class RemovalNotification<K, V>
037    extends SimpleImmutableEntry<@Nullable K, @Nullable V> {
038  private final RemovalCause cause;
039
040  /**
041   * Creates a new {@code RemovalNotification} for the given {@code key}/{@code value} pair, with
042   * the given {@code cause} for the removal. The {@code key} and/or {@code value} may be {@code
043   * null} if they were already garbage collected.
044   *
045   * @since 19.0
046   */
047  public static <K, V> RemovalNotification<K, V> create(
048      @CheckForNull K key, @CheckForNull V value, RemovalCause cause) {
049    return new RemovalNotification<>(key, value, cause);
050  }
051
052  private RemovalNotification(@CheckForNull K key, @CheckForNull V value, RemovalCause cause) {
053    super(key, value);
054    this.cause = checkNotNull(cause);
055  }
056
057  /** Returns the cause for which the entry was removed. */
058  public RemovalCause getCause() {
059    return cause;
060  }
061
062  /**
063   * Returns {@code true} if there was an automatic removal due to eviction (the cause is neither
064   * {@link RemovalCause#EXPLICIT} nor {@link RemovalCause#REPLACED}).
065   */
066  public boolean wasEvicted() {
067    return cause.wasEvicted();
068  }
069
070  private static final long serialVersionUID = 0;
071}