001/* 002 * Copyright (C) 2012 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.util.concurrent; 018 019import com.google.common.annotations.GwtIncompatible; 020import com.google.common.collect.ForwardingDeque; 021import java.util.Collection; 022import java.util.concurrent.BlockingDeque; 023import java.util.concurrent.TimeUnit; 024import javax.annotation.CheckForNull; 025 026/** 027 * A {@link BlockingDeque} which forwards all its method calls to another {@code BlockingDeque}. 028 * Subclasses should override one or more methods to modify the behavior of the backing deque as 029 * desired per the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 030 * 031 * <p><b>Warning:</b> The methods of {@code ForwardingBlockingDeque} forward <b>indiscriminately</b> 032 * to the methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change 033 * the behaviour of {@link #offer} which can lead to unexpected behaviour. In this case, you should 034 * override {@code offer} as well, either providing your own implementation, or delegating to the 035 * provided {@code standardOffer} method. 036 * 037 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code 038 * default} methods. Instead, it inherits their default implementations. When those implementations 039 * invoke methods, they invoke methods on the {@code ForwardingBlockingDeque}. 040 * 041 * <p>The {@code standard} methods are not guaranteed to be thread-safe, even when all of the 042 * methods that they depend on are thread-safe. 043 * 044 * @author Emily Soldal 045 * @since 21.0 (since 14.0 as {@link com.google.common.collect.ForwardingBlockingDeque}) 046 */ 047@GwtIncompatible 048@ElementTypesAreNonnullByDefault 049public abstract class ForwardingBlockingDeque<E> extends ForwardingDeque<E> 050 implements BlockingDeque<E> { 051 052 /** Constructor for use by subclasses. */ 053 protected ForwardingBlockingDeque() {} 054 055 @Override 056 protected abstract BlockingDeque<E> delegate(); 057 058 @Override 059 public int remainingCapacity() { 060 return delegate().remainingCapacity(); 061 } 062 063 @Override 064 public void putFirst(E e) throws InterruptedException { 065 delegate().putFirst(e); 066 } 067 068 @Override 069 public void putLast(E e) throws InterruptedException { 070 delegate().putLast(e); 071 } 072 073 @Override 074 public boolean offerFirst(E e, long timeout, TimeUnit unit) throws InterruptedException { 075 return delegate().offerFirst(e, timeout, unit); 076 } 077 078 @Override 079 public boolean offerLast(E e, long timeout, TimeUnit unit) throws InterruptedException { 080 return delegate().offerLast(e, timeout, unit); 081 } 082 083 @Override 084 public E takeFirst() throws InterruptedException { 085 return delegate().takeFirst(); 086 } 087 088 @Override 089 public E takeLast() throws InterruptedException { 090 return delegate().takeLast(); 091 } 092 093 @Override 094 @CheckForNull 095 public E pollFirst(long timeout, TimeUnit unit) throws InterruptedException { 096 return delegate().pollFirst(timeout, unit); 097 } 098 099 @Override 100 @CheckForNull 101 public E pollLast(long timeout, TimeUnit unit) throws InterruptedException { 102 return delegate().pollLast(timeout, unit); 103 } 104 105 @Override 106 public void put(E e) throws InterruptedException { 107 delegate().put(e); 108 } 109 110 @Override 111 public boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException { 112 return delegate().offer(e, timeout, unit); 113 } 114 115 @Override 116 public E take() throws InterruptedException { 117 return delegate().take(); 118 } 119 120 @Override 121 @CheckForNull 122 public E poll(long timeout, TimeUnit unit) throws InterruptedException { 123 return delegate().poll(timeout, unit); 124 } 125 126 @Override 127 public int drainTo(Collection<? super E> c) { 128 return delegate().drainTo(c); 129 } 130 131 @Override 132 public int drainTo(Collection<? super E> c, int maxElements) { 133 return delegate().drainTo(c, maxElements); 134 } 135}