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001    /*
002     * Copyright (C) 2011 The Guava Authors
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    
017    package com.google.common.cache;
018    
019    import static com.google.common.base.Preconditions.checkNotNull;
020    
021    import com.google.common.annotations.Beta;
022    import com.google.common.base.Objects;
023    
024    import java.util.Map.Entry;
025    
026    import javax.annotation.Nullable;
027    
028    /**
029     * A notification of the removal of a single entry. The key and/or value may be null if they were
030     * already garbage collected.
031     *
032     * <p>Like other {@code Map.Entry} instances associated with {@code CacheBuilder}, this class holds
033     * strong references to the key and value, regardless of the type of references the cache may be
034     * using.
035     *
036     * @author Charles Fry
037     * @since 10.0
038     */
039    @Beta
040    public final class RemovalNotification<K, V> implements Entry<K, V> {
041      @Nullable private final K key;
042      @Nullable private final V value;
043      private final RemovalCause cause;
044    
045      RemovalNotification(@Nullable K key, @Nullable V value, RemovalCause cause) {
046        this.key = key;
047        this.value = value;
048        this.cause = checkNotNull(cause);
049      }
050    
051      /**
052       * Returns the cause for which the entry was removed.
053       */
054      public RemovalCause getCause() {
055        return cause;
056      }
057    
058      /**
059       * Returns {@code true} if there was an automatic removal due to eviction (the cause is neither
060       * {@link RemovalCause#EXPLICIT} nor {@link RemovalCause#REPLACED}).
061       */
062      public boolean wasEvicted() {
063        return cause.wasEvicted();
064      }
065    
066      @Nullable @Override public K getKey() {
067        return key;
068      }
069    
070      @Nullable @Override public V getValue() {
071        return value;
072      }
073    
074      @Override public final V setValue(V value){
075        throw new UnsupportedOperationException();
076      }
077    
078      @Override public boolean equals(@Nullable Object object) {
079        if (object instanceof Entry) {
080          Entry<?, ?> that = (Entry<?, ?>) object;
081          return Objects.equal(this.getKey(), that.getKey())
082              && Objects.equal(this.getValue(), that.getValue());
083        }
084        return false;
085      }
086    
087      @Override public int hashCode() {
088        K k = getKey();
089        V v = getValue();
090        return ((k == null) ? 0 : k.hashCode()) ^ ((v == null) ? 0 : v.hashCode());
091      }
092    
093      /**
094       * Returns a string representation of the form <code>{key}={value}</code>.
095       */
096      @Override public String toString() {
097        return getKey() + "=" + getValue();
098      }
099      private static final long serialVersionUID = 0;
100    }