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 com.google.common.annotations.Beta;
020    
021    import java.util.Iterator;
022    import java.util.Map;
023    import java.util.concurrent.ConcurrentMap;
024    
025    /**
026     * The reason why a cached entry was removed.
027     *
028     * @author Charles Fry
029     * @since 10.0
030     */
031    @Beta
032    public enum RemovalCause {
033      /**
034       * The entry was manually removed by the user. This can result from the user invoking
035       * {@link Cache#invalidate}, {@link Cache#invalidateAll(Iterable)}, {@link Cache#invalidateAll()},
036       * {@link Map#remove}, {@link ConcurrentMap#remove}, or {@link Iterator#remove}.
037       */
038      EXPLICIT {
039        
040        @Override
041        boolean wasEvicted() {
042          return false;
043        }
044      },
045    
046      /**
047       * The entry itself was not actually removed, but its value was replaced by the user. This can
048       * result from the user invoking {@link Cache#put}, {@link LoadingCache#refresh}, {@link Map#put},
049       * {@link Map#putAll}, {@link ConcurrentMap#replace(Object, Object)}, or
050       * {@link ConcurrentMap#replace(Object, Object, Object)}.
051       */
052      REPLACED {
053        
054        @Override
055        boolean wasEvicted() {
056          return false;
057        }
058      },
059    
060      /**
061       * The entry was removed automatically because its key or value was garbage-collected. This
062       * can occur when using {@link CacheBuilder#weakKeys}, {@link CacheBuilder#weakValues}, or
063       * {@link CacheBuilder#softValues}.
064       */
065      COLLECTED {
066        
067        @Override
068        boolean wasEvicted() {
069          return true;
070        }
071      },
072    
073      /**
074       * The entry's expiration timestamp has passed. This can occur when using
075       * {@link CacheBuilder#expireAfterWrite} or {@link CacheBuilder#expireAfterAccess}.
076       */
077      EXPIRED {
078        
079        @Override
080        boolean wasEvicted() {
081          return true;
082        }
083      },
084    
085      /**
086       * The entry was evicted due to size constraints. This can occur when using
087       * {@link CacheBuilder#maximumSize} or {@link CacheBuilder#maximumWeight}.
088       */
089      SIZE {
090        
091        @Override
092        boolean wasEvicted() {
093          return true;
094        }
095      };
096    
097      /**
098       * Returns {@code true} if there was an automatic removal due to eviction (the cause is neither
099       * {@link #EXPLICIT} nor {@link #REPLACED}).
100       */
101      abstract boolean wasEvicted();
102    }