/*
 * 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.GwtIncompatible;
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 Cache interface to minimize the effort required to implement this interface.

To implement a cache, the programmer needs only to extend this class and provide an implementation for the LoadingCache.get(Object) and Cache.getIfPresent methods. getUnchecked, AbstractCache.get(Object, Callable), and getAll are implemented in terms of get; AbstractCache.getAllPresent is implemented in terms of getIfPresent; AbstractCache.putAll is implemented in terms of AbstractCache.put, AbstractCache.invalidateAll(Iterable) is implemented in terms of AbstractCache.invalidate. The method AbstractCache.cleanUp is a no-op. All other methods throw an UnsupportedOperationException.

Author:Charles Fry
Since:11.0
/** * 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 */
@GwtIncompatible public abstract class AbstractLoadingCache<K, V> extends AbstractCache<K, V> implements LoadingCache<K, V> {
Constructor for use by subclasses.
/** 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(); } }