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}