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.annotations.J2ktIncompatible; 021import com.google.common.collect.ForwardingDeque; 022import java.util.Collection; 023import java.util.concurrent.BlockingDeque; 024import java.util.concurrent.TimeUnit; 025import javax.annotation.CheckForNull; 026 027/** 028 * A {@link BlockingDeque} which forwards all its method calls to another {@code BlockingDeque}. 029 * Subclasses should override one or more methods to modify the behavior of the backing deque as 030 * desired per the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 031 * 032 * <p><b>Warning:</b> The methods of {@code ForwardingBlockingDeque} forward <b>indiscriminately</b> 033 * to the methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change 034 * the behaviour of {@link #offer} which can lead to unexpected behaviour. In this case, you should 035 * override {@code offer} as well, either providing your own implementation, or delegating to the 036 * provided {@code standardOffer} method. 037 * 038 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code 039 * default} methods. Instead, it inherits their default implementations. When those implementations 040 * invoke methods, they invoke methods on the {@code ForwardingBlockingDeque}. 041 * 042 * <p>The {@code standard} methods are not guaranteed to be thread-safe, even when all of the 043 * methods that they depend on are thread-safe. 044 * 045 * @author Emily Soldal 046 * @since 21.0 (since 14.0 as {@link com.google.common.collect.ForwardingBlockingDeque}) 047 */ 048@J2ktIncompatible 049@GwtIncompatible 050@ElementTypesAreNonnullByDefault 051public abstract class ForwardingBlockingDeque<E> extends ForwardingDeque<E> 052 implements BlockingDeque<E> { 053 054 /** Constructor for use by subclasses. */ 055 protected ForwardingBlockingDeque() {} 056 057 @Override 058 protected abstract BlockingDeque<E> delegate(); 059 060 @Override 061 public int remainingCapacity() { 062 return delegate().remainingCapacity(); 063 } 064 065 @Override 066 public void putFirst(E e) throws InterruptedException { 067 delegate().putFirst(e); 068 } 069 070 @Override 071 public void putLast(E e) throws InterruptedException { 072 delegate().putLast(e); 073 } 074 075 @Override 076 public boolean offerFirst(E e, long timeout, TimeUnit unit) throws InterruptedException { 077 return delegate().offerFirst(e, timeout, unit); 078 } 079 080 @Override 081 public boolean offerLast(E e, long timeout, TimeUnit unit) throws InterruptedException { 082 return delegate().offerLast(e, timeout, unit); 083 } 084 085 @Override 086 public E takeFirst() throws InterruptedException { 087 return delegate().takeFirst(); 088 } 089 090 @Override 091 public E takeLast() throws InterruptedException { 092 return delegate().takeLast(); 093 } 094 095 @Override 096 @CheckForNull 097 public E pollFirst(long timeout, TimeUnit unit) throws InterruptedException { 098 return delegate().pollFirst(timeout, unit); 099 } 100 101 @Override 102 @CheckForNull 103 public E pollLast(long timeout, TimeUnit unit) throws InterruptedException { 104 return delegate().pollLast(timeout, unit); 105 } 106 107 @Override 108 public void put(E e) throws InterruptedException { 109 delegate().put(e); 110 } 111 112 @Override 113 public boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException { 114 return delegate().offer(e, timeout, unit); 115 } 116 117 @Override 118 public E take() throws InterruptedException { 119 return delegate().take(); 120 } 121 122 @Override 123 @CheckForNull 124 public E poll(long timeout, TimeUnit unit) throws InterruptedException { 125 return delegate().poll(timeout, unit); 126 } 127 128 @Override 129 public int drainTo(Collection<? super E> c) { 130 return delegate().drainTo(c); 131 } 132 133 @Override 134 public int drainTo(Collection<? super E> c, int maxElements) { 135 return delegate().drainTo(c, maxElements); 136 } 137}