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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.collect.ImmutableMap;
import com.google.common.collect.Maps;
import com.google.common.util.concurrent.UncheckedExecutionException;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
/**
* This class provides a skeletal implementation of the {@code Cache} interface to minimize the
* effort required to implement this interface.
*
* <p>To implement a cache, the programmer needs only to extend this class and provide an
* implementation for the {@link #get} and {@link #getIfPresent} methods. {@link #getUnchecked},
* {@link #get(K, Callable)}, and {@link #getAll} are implemented in terms of {@code get};
* {@link #getAllPresent} is implemented in terms of {@code get}; {@link #invalidateAll(Iterable)}
* is implemented in terms of {@link #invalidate}. The method {@link #cleanUp} is a no-op. All other
* methods throw an {@link UnsupportedOperationException}.
*
* @author Charles Fry
* @since 11.0
*/
@Beta
public abstract class AbstractLoadingCache<K, V>
extends AbstractCache<K, V> implements LoadingCache<K, V> {
/** Constructor for use by subclasses. */
protected AbstractLoadingCache() {}
@Override
public V getUnchecked(K key) {
try {
return get(key);
} catch (ExecutionException e) {
throw new UncheckedExecutionException(e.getCause());
}
}
@Override
public ImmutableMap<K, V> getAll(Iterable<? extends K> keys) throws ExecutionException {
Map<K, V> result = Maps.newLinkedHashMap();
for (K key : keys) {
if (!result.containsKey(key)) {
result.put(key, get(key));
}
}
return ImmutableMap.copyOf(result);
}
@Override
public final V apply(K key) {
return getUnchecked(key);
}
@Override
public void refresh(K key) {
throw new UnsupportedOperationException();
}
}
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