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      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 import com.google.common.annotations.GwtCompatible;
     23 import com.google.common.base.Objects;
     24 
     25 import java.util.Map.Entry;
     26 
     27 import javax.annotation.Nullable;
     28 
     29 /**
     30  * A notification of the removal of a single entry. The key and/or value may be null if they were
     31  * already garbage collected.
     32  *
     33  * <p>Like other {@code Map.Entry} instances associated with {@code CacheBuilder}, this class holds
     34  * strong references to the key and value, regardless of the type of references the cache may be
     35  * using.
     36  *
     37  * @author Charles Fry
     38  * @since 10.0
     39  */
     40 @Beta
     41 @GwtCompatible
     42 public final class RemovalNotification<K, V> implements Entry<K, V> {
     43   @Nullable private final K key;
     44   @Nullable private final V value;
     45   private final RemovalCause cause;
     46 
     47   RemovalNotification(@Nullable K key, @Nullable V value, RemovalCause cause) {
     48     this.key = key;
     49     this.value = value;
     50     this.cause = checkNotNull(cause);
     51   }
     52 
     53   /**
     54    * Returns the cause for which the entry was removed.
     55    */
     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   @Nullable @Override public K getKey() {
     69     return key;
     70   }
     71 
     72   @Nullable @Override public V getValue() {
     73     return value;
     74   }
     75 
     76   @Override public final V setValue(V value) {
     77     throw new UnsupportedOperationException();
     78   }
     79 
     80   @Override public boolean equals(@Nullable Object object) {
     81     if (object instanceof Entry) {
     82       Entry<?, ?> that = (Entry<?, ?>) object;
     83       return Objects.equal(this.getKey(), that.getKey())
     84           && Objects.equal(this.getValue(), that.getValue());
     85     }
     86     return false;
     87   }
     88 
     89   @Override public int hashCode() {
     90     K k = getKey();
     91     V v = getValue();
     92     return ((k == null) ? 0 : k.hashCode()) ^ ((v == null) ? 0 : v.hashCode());
     93   }
     94 
     95   /**
     96    * Returns a string representation of the form <code>{key}={value}</code>.
     97    */
     98   @Override public String toString() {
     99     return getKey() + "=" + getValue();
    100   }
    101   private static final long serialVersionUID = 0;
    102 }
    103