    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 {@link
    035       * Cache#invalidate}, {@link Map#remove}, {@link ConcurrentMap#remove}, or {@link
    036       * Iterator#remove}.
    037       */
    038      EXPLICIT {
    039        @Override
    040        boolean wasEvicted() {
    041          return false;
    042        }
    043      },
    044
    045      /**
    046       * The entry itself was not actually removed, but its value was replaced by the user. This can
    047       * result from the user invoking {@link Map#put}, {@link Map#putAll},
    048       * {@link ConcurrentMap#replace(Object, Object)}, or
    049       * {@link ConcurrentMap#replace(Object, Object, Object)}.
    050       */
    051      REPLACED {
    052        @Override
    053        boolean wasEvicted() {
    054          return false;
    055        }
    056      },
    057
    058      /**
    059       * The entry was removed automatically because its key or value was garbage-collected. This
    060       * can occur when using {@link CacheBuilder#weakKeys}, {@link CacheBuilder#weakValues}, or
    061       * {@link CacheBuilder#softValues}.
    062       */
    063      COLLECTED {
    064        @Override
    065        boolean wasEvicted() {
    066          return true;
    067        }
    068      },
    069
    070      /**
    071       * The entry's expiration timestamp has passed. This can occur when using {@link
    072       * CacheBuilder#expireAfterWrite} or {@link CacheBuilder#expireAfterAccess}.
    073       */
    074      EXPIRED {
    075        @Override
    076        boolean wasEvicted() {
    077          return true;
    078        }
    079      },
    080
    081      /**
    082       * The entry was evicted due to size constraints. This can occur when using {@link
    083       * CacheBuilder#maximumSize}.
    084       */
    085      SIZE {
    086        @Override
    087        boolean wasEvicted() {
    088          return true;
    089        }
    090      };
    091
    092      /**
    093       * Returns {@code true} if there was an automatic removal due to eviction (the cause is neither
    094       * {@link #EXPLICIT} nor {@link #REPLACED}).
    095       */
    096      abstract boolean wasEvicted();
    097    }