001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.reef.util.cache;
020
021import java.util.concurrent.Callable;
022import java.util.concurrent.ExecutionException;
023
024/**
025 * Cache with get-if-absent-compute semantics.
026 * Supports explicit invalidation.
027 * Implementation may add other features, e.g. eviction on expire-after-write
028 */
029public interface Cache<K, V> {
030  /**
031   * Returns a value for the key if cached; otherwise creates, caches and returns.
032   * When it creates a value for a key, only one callable for the key is executed
033   *
034   * @param key          a key
035   * @param valueFetcher a value fetcher
036   * @return a value
037   * @throws ExecutionException
038   */
039  V get(K key, Callable<V> valueFetcher) throws ExecutionException;
040
041  /**
042   * Invalidates a key from the cache.
043   *
044   * @param key a key
045   */
046  void invalidate(K key);
047
048}