001/* 002 * Copyright (C) 2007 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package com.google.common.collect; 018 019import com.google.common.annotations.GwtCompatible; 020import com.google.errorprone.annotations.CanIgnoreReturnValue; 021import java.util.concurrent.ConcurrentMap; 022import javax.annotation.CheckForNull; 023 024/** 025 * A concurrent map which forwards all its method calls to another concurrent map. Subclasses should 026 * override one or more methods to modify the behavior of the backing map as desired per the <a 027 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 028 * 029 * <p><b>{@code default} method warning:</b> This class forwards calls to <i>only some</i> {@code 030 * default} methods. Specifically, it forwards calls only for methods that existed <a 031 * href="https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentMap.html">before 032 * {@code default} methods were introduced</a>. For newer methods, like {@code forEach}, it inherits 033 * their default implementations. When those implementations invoke methods, they invoke methods on 034 * the {@code ForwardingConcurrentMap}. 035 * 036 * @author Charles Fry 037 * @since 2.0 038 */ 039@GwtCompatible 040@ElementTypesAreNonnullByDefault 041public abstract class ForwardingConcurrentMap<K, V> extends ForwardingMap<K, V> 042 implements ConcurrentMap<K, V> { 043 044 /** Constructor for use by subclasses. */ 045 protected ForwardingConcurrentMap() {} 046 047 @Override 048 protected abstract ConcurrentMap<K, V> delegate(); 049 050 @CanIgnoreReturnValue 051 @Override 052 @CheckForNull 053 public V putIfAbsent(K key, V value) { 054 return delegate().putIfAbsent(key, value); 055 } 056 057 @CanIgnoreReturnValue 058 @Override 059 public boolean remove(@CheckForNull Object key, @CheckForNull Object value) { 060 return delegate().remove(key, value); 061 } 062 063 @CanIgnoreReturnValue 064 @Override 065 @CheckForNull 066 public V replace(K key, V value) { 067 return delegate().replace(key, value); 068 } 069 070 @CanIgnoreReturnValue 071 @Override 072 public boolean replace(K key, V oldValue, V newValue) { 073 return delegate().replace(key, oldValue, newValue); 074 } 075}