| /* |
| * 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.annotations.GwtCompatible; |
| import com.google.common.collect.ImmutableMap; |
| import com.google.common.util.concurrent.ExecutionError; |
| import com.google.common.util.concurrent.UncheckedExecutionException; |
| |
| import java.util.Map; |
| import java.util.concurrent.Callable; |
| import java.util.concurrent.ConcurrentMap; |
| import java.util.concurrent.ExecutionException; |
| |
| import javax.annotation.Nullable; |
| |
| /** |
| * A semi-persistent mapping from keys to values. Cache entries are manually added using |
| * {@link #get(Object, Callable)} or {@link #put(Object, Object)}, and are stored in the cache until |
| * either evicted or manually invalidated. |
| * |
| * <p>Implementations of this interface are expected to be thread-safe, and can be safely accessed |
| * by multiple concurrent threads. |
| * |
| * <p>Note that while this class is still annotated as {@link Beta}, the API is frozen from a |
| * consumer's standpoint. In other words existing methods are all considered {@code non-Beta} and |
| * won't be changed without going through an 18 month deprecation cycle; however new methods may be |
| * added at any time. |
| * |
| * @author Charles Fry |
| * @since 10.0 |
| */ |
| @Beta |
| @GwtCompatible |
| public interface Cache<K, V> { |
| |
| /** |
| * Returns the value associated with {@code key} in this cache, or {@code null} if there is no |
| * cached value for {@code key}. |
| * |
| * @since 11.0 |
| */ |
| @Nullable |
| V getIfPresent(Object key); |
| |
| /** |
| * Returns the value associated with {@code key} in this cache, obtaining that value from |
| * {@code valueLoader} if necessary. No observable state associated with this cache is modified |
| * until loading completes. This method provides a simple substitute for the conventional |
| * "if cached, return; otherwise create, cache and return" pattern. |
| * |
| * <p><b>Warning:</b> as with {@link CacheLoader#load}, {@code valueLoader} <b>must not</b> return |
| * {@code null}; it may either return a non-null value or throw an exception. |
| * |
| * @throws ExecutionException if a checked exception was thrown while loading the value |
| * @throws UncheckedExecutionException if an unchecked exception was thrown while loading the |
| * value |
| * @throws ExecutionError if an error was thrown while loading the value |
| * |
| * @since 11.0 |
| */ |
| V get(K key, Callable<? extends V> valueLoader) throws ExecutionException; |
| |
| /** |
| * Returns a map of the values associated with {@code keys} in this cache. The returned map will |
| * only contain entries which are already present in the cache. |
| * |
| * @since 11.0 |
| */ |
| ImmutableMap<K, V> getAllPresent(Iterable<?> keys); |
| |
| /** |
| * Associates {@code value} with {@code key} in this cache. If the cache previously contained a |
| * value associated with {@code key}, the old value is replaced by {@code value}. |
| * |
| * <p>Prefer {@link #get(Object, Callable)} when using the conventional "if cached, return; |
| * otherwise create, cache and return" pattern. |
| * |
| * @since 11.0 |
| */ |
| void put(K key, V value); |
| |
| /** |
| * Copies all of the mappings from the specified map to the cache. The effect of this call is |
| * equivalent to that of calling {@code put(k, v)} on this map once for each mapping from key |
| * {@code k} to value {@code v} in the specified map. The behavior of this operation is undefined |
| * if the specified map is modified while the operation is in progress. |
| * |
| * @since 12.0 |
| */ |
| void putAll(Map<? extends K,? extends V> m); |
| |
| /** |
| * Discards any cached value for key {@code key}. |
| */ |
| void invalidate(Object key); |
| |
| /** |
| * Discards any cached values for keys {@code keys}. |
| * |
| * @since 11.0 |
| */ |
| void invalidateAll(Iterable<?> keys); |
| |
| /** |
| * Discards all entries in the cache. |
| */ |
| void invalidateAll(); |
| |
| /** |
| * Returns the approximate number of entries in this cache. |
| */ |
| long size(); |
| |
| /** |
| * Returns a current snapshot of this cache's cumulative statistics. All stats are initialized |
| * to zero, and are monotonically increasing over the lifetime of the cache. |
| * |
| */ |
| CacheStats stats(); |
| |
| /** |
| * Returns a view of the entries stored in this cache as a thread-safe map. Modifications made to |
| * the map directly affect the cache. |
| * |
| * <p>Iterators from the returned map are at least <i>weakly consistent</i>: they are safe for |
| * concurrent use, but if the cache is modified (including by eviction) after the iterator is |
| * created, it is undefined which of the changes (if any) will be reflected in that iterator. |
| */ |
| ConcurrentMap<K, V> asMap(); |
| |
| /** |
| * Performs any pending maintenance operations needed by the cache. Exactly which activities are |
| * performed -- if any -- is implementation-dependent. |
| */ |
| void cleanUp(); |
| } |