com.google.common.cache.AbstractLoadingCache.java Source code

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Here is the source code for com.google.common.cache.AbstractLoadingCache.java

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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.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(Object)} and {@link #getIfPresent} methods.
 * {@link #getUnchecked}, {@link #get(Object, Callable)}, and {@link #getAll} are implemented in
 * terms of {@code get}; {@link #getAllPresent} is implemented in terms of {@code getIfPresent};
 * {@link #putAll} is implemented in terms of {@link #put}, {@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
 */
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();
    }
}