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/*
* Copyright (C) 2011 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.cache;
import com.google.common.annotations.Beta;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import java.util.concurrent.ExecutionException;
/**
* A cache which forwards all its method calls to another cache. Subclasses should override one or
* more methods to modify the behavior of the backing cache as desired per the
* <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
*
* <p>Note that {@link #get}, {@link #getUnchecked}, and {@link #apply} all expose the same
* underlying functionality, so should probably be overridden as a group.
*
* @author Charles Fry
* @since 11.0
*/
@Beta
public abstract class ForwardingLoadingCache<K, V>
extends ForwardingCache<K, V> implements LoadingCache<K, V> {
/** Constructor for use by subclasses. */
protected ForwardingLoadingCache() {}
@Override
protected abstract LoadingCache<K, V> delegate();
@Override
public V get(K key) throws ExecutionException {
return delegate().get(key);
}
@Override
public V getUnchecked(K key) {
return delegate().getUnchecked(key);
}
@Override
public ImmutableMap<K, V> getAll(Iterable<? extends K> keys) throws ExecutionException {
return delegate().getAll(keys);
}
@Override
public V apply(K key) {
return delegate().apply(key);
}
@Override
public void refresh(K key) {
delegate().refresh(key);
}
/**
* A simplified version of {@link ForwardingLoadingCache} where subclasses can pass in an already
* constructed {@link LoadingCache} as the delegete.
*
* @since 10.0
*/
@Beta
public abstract static class SimpleForwardingLoadingCache<K, V>
extends ForwardingLoadingCache<K, V> {
private final LoadingCache<K, V> delegate;
protected SimpleForwardingLoadingCache(LoadingCache<K, V> delegate) {
this.delegate = Preconditions.checkNotNull(delegate);
}
@Override
protected final LoadingCache<K, V> delegate() {
return delegate;
}
}
}
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