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
026 * should override one or more methods to modify the behavior of the backing
027 * deque as desired per the <a
028 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
029 *
030 * <p><b>Warning:</b> The methods of {@code ForwardingDeque} forward
031 * <b>indiscriminately</b> to the methods of the delegate. For example,
032 * overriding {@link #add} alone <b>will not</b> change the behavior of {@link
033 * #offer} which can lead to unexpected behavior. In this case, you should
034 * override {@code offer} as well.
035 *
036 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
037 * default} methods. Instead, it inherits their default implementations. When those implementations
038 * invoke methods, they invoke methods on the {@code ForwardingDeque}.
039 *
040 * @author Kurt Alfred Kluever
041 * @since 12.0
042 */
043@GwtIncompatible
044public abstract class ForwardingDeque<E> extends ForwardingQueue<E> implements Deque<E> {
045
046  /** Constructor for use by subclasses. */
047  protected ForwardingDeque() {}
048
049  @Override
050  protected abstract Deque<E> delegate();
051
052  @Override
053  public void addFirst(E e) {
054    delegate().addFirst(e);
055  }
056
057  @Override
058  public void addLast(E e) {
059    delegate().addLast(e);
060  }
061
062  @Override
063  public Iterator<E> descendingIterator() {
064    return delegate().descendingIterator();
065  }
066
067  @Override
068  public E getFirst() {
069    return delegate().getFirst();
070  }
071
072  @Override
073  public E getLast() {
074    return delegate().getLast();
075  }
076
077  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
078  @Override
079  public boolean offerFirst(E e) {
080    return delegate().offerFirst(e);
081  }
082
083  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
084  @Override
085  public boolean offerLast(E e) {
086    return delegate().offerLast(e);
087  }
088
089  @Override
090  public E peekFirst() {
091    return delegate().peekFirst();
092  }
093
094  @Override
095  public E peekLast() {
096    return delegate().peekLast();
097  }
098
099  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
100  @Override
101  public E pollFirst() {
102    return delegate().pollFirst();
103  }
104
105  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
106  @Override
107  public E pollLast() {
108    return delegate().pollLast();
109  }
110
111  @CanIgnoreReturnValue
112  @Override
113  public E pop() {
114    return delegate().pop();
115  }
116
117  @Override
118  public void push(E e) {
119    delegate().push(e);
120  }
121
122  @CanIgnoreReturnValue
123  @Override
124  public E removeFirst() {
125    return delegate().removeFirst();
126  }
127
128  @CanIgnoreReturnValue
129  @Override
130  public E removeLast() {
131    return delegate().removeLast();
132  }
133
134  @CanIgnoreReturnValue
135  @Override
136  public boolean removeFirstOccurrence(Object o) {
137    return delegate().removeFirstOccurrence(o);
138  }
139
140  @CanIgnoreReturnValue
141  @Override
142  public boolean removeLastOccurrence(Object o) {
143    return delegate().removeLastOccurrence(o);
144  }
145}