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.collect;
018
019import com.google.common.annotations.GwtIncompatible;
020import com.google.errorprone.annotations.CanIgnoreReturnValue;
021import java.util.Deque;
022import java.util.Iterator;
023
024/**
025 * A deque which forwards all its method calls to another deque. Subclasses should override one or
026 * more methods to modify the behavior of the backing deque as desired per the <a
027 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
028 *
029 * <p><b>Warning:</b> The methods of {@code ForwardingDeque} forward <b>indiscriminately</b> to the
030 * methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change the
031 * behavior of {@link #offer} which can lead to unexpected behavior. In this case, you should
032 * override {@code offer} as well.
033 *
034 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
035 * default} methods. Instead, it inherits their default implementations. When those implementations
036 * invoke methods, they invoke methods on the {@code ForwardingDeque}.
037 *
038 * @author Kurt Alfred Kluever
039 * @since 12.0
040 */
041@GwtIncompatible
042public abstract class ForwardingDeque<E> extends ForwardingQueue<E> implements Deque<E> {
043
044  /** Constructor for use by subclasses. */
045  protected ForwardingDeque() {}
046
047  @Override
048  protected abstract Deque<E> delegate();
049
050  @Override
051  public void addFirst(E e) {
052    delegate().addFirst(e);
053  }
054
055  @Override
056  public void addLast(E e) {
057    delegate().addLast(e);
058  }
059
060  @Override
061  public Iterator<E> descendingIterator() {
062    return delegate().descendingIterator();
063  }
064
065  @Override
066  public E getFirst() {
067    return delegate().getFirst();
068  }
069
070  @Override
071  public E getLast() {
072    return delegate().getLast();
073  }
074
075  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
076  @Override
077  public boolean offerFirst(E e) {
078    return delegate().offerFirst(e);
079  }
080
081  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
082  @Override
083  public boolean offerLast(E e) {
084    return delegate().offerLast(e);
085  }
086
087  @Override
088  public E peekFirst() {
089    return delegate().peekFirst();
090  }
091
092  @Override
093  public E peekLast() {
094    return delegate().peekLast();
095  }
096
097  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
098  @Override
099  public E pollFirst() {
100    return delegate().pollFirst();
101  }
102
103  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
104  @Override
105  public E pollLast() {
106    return delegate().pollLast();
107  }
108
109  @CanIgnoreReturnValue
110  @Override
111  public E pop() {
112    return delegate().pop();
113  }
114
115  @Override
116  public void push(E e) {
117    delegate().push(e);
118  }
119
120  @CanIgnoreReturnValue
121  @Override
122  public E removeFirst() {
123    return delegate().removeFirst();
124  }
125
126  @CanIgnoreReturnValue
127  @Override
128  public E removeLast() {
129    return delegate().removeLast();
130  }
131
132  @CanIgnoreReturnValue
133  @Override
134  public boolean removeFirstOccurrence(Object o) {
135    return delegate().removeFirstOccurrence(o);
136  }
137
138  @CanIgnoreReturnValue
139  @Override
140  public boolean removeLastOccurrence(Object o) {
141    return delegate().removeLastOccurrence(o);
142  }
143}