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, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018package org.apache.hadoop.hbase.util; 019 020import java.io.IOException; 021import java.util.concurrent.ConcurrentMap; 022import java.util.function.Supplier; 023import org.apache.yetus.audience.InterfaceAudience; 024 025/** 026 * Utility methods for dealing with Collections, including treating null collections as empty. 027 */ 028@InterfaceAudience.Private 029public class ConcurrentMapUtils { 030 031 /** 032 * In HBASE-16648 we found that ConcurrentHashMap.get is much faster than computeIfAbsent if the 033 * value already exists. Notice that the implementation does not guarantee that the supplier will 034 * only be executed once. 035 */ 036 public static <K, V> V computeIfAbsent(ConcurrentMap<K, V> map, K key, Supplier<V> supplier) { 037 return computeIfAbsent(map, key, supplier, () -> { 038 }); 039 } 040 041 /** 042 * A supplier that throws IOException when get. 043 */ 044 @FunctionalInterface 045 public interface IOExceptionSupplier<V> { 046 V get() throws IOException; 047 } 048 049 /** 050 * In HBASE-16648 we found that ConcurrentHashMap.get is much faster than computeIfAbsent if the 051 * value already exists. So here we copy the implementation of 052 * {@link ConcurrentMap#computeIfAbsent(Object, java.util.function.Function)}. It uses get and 053 * putIfAbsent to implement computeIfAbsent. And notice that the implementation does not guarantee 054 * that the supplier will only be executed once. 055 */ 056 public static <K, V> V computeIfAbsentEx(ConcurrentMap<K, V> map, K key, 057 IOExceptionSupplier<V> supplier) throws IOException { 058 V v, newValue; 059 return ((v = map.get(key)) == null && (newValue = supplier.get()) != null 060 && (v = map.putIfAbsent(key, newValue)) == null) ? newValue : v; 061 } 062 063 public static <K, V> V computeIfAbsent(ConcurrentMap<K, V> map, K key, Supplier<V> supplier, 064 Runnable actionIfAbsent) { 065 V v = map.get(key); 066 if (v != null) { 067 return v; 068 } 069 V newValue = supplier.get(); 070 v = map.putIfAbsent(key, newValue); 071 if (v != null) { 072 return v; 073 } 074 actionIfAbsent.run(); 075 return newValue; 076 } 077}