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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 com.google.common.annotations.Beta;
020    import com.google.common.base.Preconditions;
021    import com.google.common.collect.ForwardingObject;
022    import com.google.common.collect.ImmutableMap;
023    
024    import java.util.concurrent.Callable;
025    import java.util.concurrent.ConcurrentMap;
026    import java.util.concurrent.ExecutionException;
027    
028    import javax.annotation.Nullable;
029    
030    /**
031     * A cache which forwards all its method calls to another cache. Subclasses should override one or
032     * more methods to modify the behavior of the backing cache as desired per the
033     * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
034     *
035     * @author Charles Fry
036     * @since 10.0
037     */
038    @Beta
039    public abstract class ForwardingCache<K, V> extends ForwardingObject implements Cache<K, V> {
040    
041      /** Constructor for use by subclasses. */
042      protected ForwardingCache() {}
043    
044      @Override
045      protected abstract Cache<K, V> delegate();
046    
047      /**
048       * @since 11.0
049       */
050      @Override
051      @Nullable
052      public V getIfPresent(K key) {
053        return delegate().getIfPresent(key);
054      }
055    
056      /**
057       * @since 11.0
058       */
059      @Override
060      public V get(K key, Callable<? extends V> valueLoader) throws ExecutionException {
061        return delegate().get(key, valueLoader);
062      }
063    
064      /**
065       * @since 11.0
066       */
067      @Override
068      public ImmutableMap<K, V> getAllPresent(Iterable<? extends K> keys) {
069        return delegate().getAllPresent(keys);
070      }
071    
072      /**
073       * @since 11.0
074       */
075      @Override
076      public void put(K key, V value) {
077        delegate().put(key, value);
078      }
079    
080      @Override
081      public void invalidate(Object key) {
082        delegate().invalidate(key);
083      }
084    
085      /**
086       * @since 11.0
087       */
088      @Override
089      public void invalidateAll(Iterable<?> keys) {
090        delegate().invalidateAll(keys);
091      }
092    
093      @Override
094      public void invalidateAll() {
095        delegate().invalidateAll();
096      }
097    
098      @Override
099      public long size() {
100        return delegate().size();
101      }
102    
103      @Override
104      public CacheStats stats() {
105        return delegate().stats();
106      }
107    
108      @Override
109      public ConcurrentMap<K, V> asMap() {
110        return delegate().asMap();
111      }
112    
113      @Override
114      public void cleanUp() {
115        delegate().cleanUp();
116      }
117    
118      @Deprecated
119      @Override
120      public V get(K key) throws ExecutionException {
121        return delegate().get(key);
122      }
123    
124      @Deprecated
125      @Override
126      public V getUnchecked(K key) {
127        return delegate().getUnchecked(key);
128      }
129    
130      @Deprecated
131      @Override
132      public V apply(K key) {
133        return delegate().apply(key);
134      }
135    
136      /**
137       * A simplified version of {@link ForwardingCache} where subclasses can pass in an already
138       * constructed {@link Cache} as the delegete.
139       *
140       * @since 10.0
141       */
142      @Beta
143      public abstract static class SimpleForwardingCache<K, V> extends ForwardingCache<K, V> {
144        private final Cache<K, V> delegate;
145    
146        protected SimpleForwardingCache(Cache<K, V> delegate) {
147          this.delegate = Preconditions.checkNotNull(delegate);
148        }
149    
150        @Override
151        protected final Cache<K, V> delegate() {
152          return delegate;
153        }
154      }
155    }