001/*
002 * Copyright (C) 2011 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the
010 * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
011 * express or implied. See the License for the specific language governing permissions and
012 * limitations under the License.
013 */
014
015package com.google.common.collect;
016
017import com.google.common.annotations.Beta;
018import com.google.common.annotations.GwtCompatible;
019import java.util.Comparator;
020import java.util.Iterator;
021import java.util.NavigableSet;
022
023/**
024 * A sorted multiset which forwards all its method calls to another sorted multiset. Subclasses
025 * should override one or more methods to modify the behavior of the backing multiset as desired
026 * per the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
027 *
028 * <p><b>Warning:</b> The methods of {@code ForwardingSortedMultiset} forward
029 * <b>indiscriminately</b> to the methods of the delegate. For example, overriding
030 * {@link #add(Object, int)} alone <b>will not</b> change the behavior of {@link #add(Object)},
031 * which can lead to unexpected behavior. In this case, you should override {@code add(Object)} as
032 * well, either providing your own implementation, or delegating to the provided {@code
033 * standardAdd} method.
034 *
035 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
036 * default} methods. Instead, it inherits their default implementations. When those implementations
037 * invoke methods, they invoke methods on the {@code ForwardingSortedMultiset}.
038 *
039 * <p>The {@code standard} methods and any collection views they return are not guaranteed to be
040 * thread-safe, even when all of the methods that they depend on are thread-safe.
041 *
042 * @author Louis Wasserman
043 * @since 15.0
044 */
045@Beta
046@GwtCompatible(emulated = true)
047public abstract class ForwardingSortedMultiset<E> extends ForwardingMultiset<E>
048    implements SortedMultiset<E> {
049  /** Constructor for use by subclasses. */
050  protected ForwardingSortedMultiset() {}
051
052  @Override
053  protected abstract SortedMultiset<E> delegate();
054
055  @Override
056  public NavigableSet<E> elementSet() {
057    return (NavigableSet<E>) super.elementSet();
058  }
059
060  /**
061   * A sensible implementation of {@link SortedMultiset#elementSet} in terms of the following
062   * methods: {@link SortedMultiset#clear}, {@link SortedMultiset#comparator}, {@link
063   * SortedMultiset#contains}, {@link SortedMultiset#containsAll}, {@link SortedMultiset#count},
064   * {@link SortedMultiset#firstEntry} {@link SortedMultiset#headMultiset}, {@link
065   * SortedMultiset#isEmpty}, {@link SortedMultiset#lastEntry}, {@link SortedMultiset#subMultiset},
066   * {@link SortedMultiset#tailMultiset}, the {@code size()} and {@code iterator()} methods of
067   * {@link SortedMultiset#entrySet}, and {@link SortedMultiset#remove(Object, int)}. In many
068   * situations, you may wish to override {@link SortedMultiset#elementSet} to forward to this
069   * implementation or a subclass thereof.
070   */
071  protected class StandardElementSet extends SortedMultisets.NavigableElementSet<E> {
072    /** Constructor for use by subclasses. */
073    public StandardElementSet() {
074      super(ForwardingSortedMultiset.this);
075    }
076  }
077
078  @Override
079  public Comparator<? super E> comparator() {
080    return delegate().comparator();
081  }
082
083  @Override
084  public SortedMultiset<E> descendingMultiset() {
085    return delegate().descendingMultiset();
086  }
087
088  /**
089   * A skeleton implementation of a descending multiset view. Normally,
090   * {@link #descendingMultiset()} will not reflect any changes you make to the behavior of methods
091   * such as {@link #add(Object)} or {@link #pollFirstEntry}. This skeleton implementation
092   * correctly delegates each of its operations to the appropriate methods of this {@code
093   * ForwardingSortedMultiset}.
094   *
095   * In many cases, you may wish to override {@link #descendingMultiset()} to return an instance of
096   * a subclass of {@code StandardDescendingMultiset}.
097   */
098  protected abstract class StandardDescendingMultiset extends DescendingMultiset<E> {
099    /** Constructor for use by subclasses. */
100    public StandardDescendingMultiset() {}
101
102    @Override
103    SortedMultiset<E> forwardMultiset() {
104      return ForwardingSortedMultiset.this;
105    }
106  }
107
108  @Override
109  public Entry<E> firstEntry() {
110    return delegate().firstEntry();
111  }
112
113  /**
114   * A sensible definition of {@link #firstEntry()} in terms of {@code entrySet().iterator()}.
115   *
116   * If you override {@link #entrySet()}, you may wish to override {@link #firstEntry()} to forward
117   * to this implementation.
118   */
119  protected Entry<E> standardFirstEntry() {
120    Iterator<Entry<E>> entryIterator = entrySet().iterator();
121    if (!entryIterator.hasNext()) {
122      return null;
123    }
124    Entry<E> entry = entryIterator.next();
125    return Multisets.immutableEntry(entry.getElement(), entry.getCount());
126  }
127
128  @Override
129  public Entry<E> lastEntry() {
130    return delegate().lastEntry();
131  }
132
133  /**
134   * A sensible definition of {@link #lastEntry()} in terms of {@code
135   * descendingMultiset().entrySet().iterator()}.
136   *
137   * If you override {@link #descendingMultiset} or {@link #entrySet()}, you may wish to override
138   * {@link #firstEntry()} to forward to this implementation.
139   */
140  protected Entry<E> standardLastEntry() {
141    Iterator<Entry<E>> entryIterator = descendingMultiset().entrySet().iterator();
142    if (!entryIterator.hasNext()) {
143      return null;
144    }
145    Entry<E> entry = entryIterator.next();
146    return Multisets.immutableEntry(entry.getElement(), entry.getCount());
147  }
148
149  @Override
150  public Entry<E> pollFirstEntry() {
151    return delegate().pollFirstEntry();
152  }
153
154  /**
155   * A sensible definition of {@link #pollFirstEntry()} in terms of {@code entrySet().iterator()}.
156   *
157   * If you override {@link #entrySet()}, you may wish to override {@link #pollFirstEntry()} to
158   * forward to this implementation.
159   */
160  protected Entry<E> standardPollFirstEntry() {
161    Iterator<Entry<E>> entryIterator = entrySet().iterator();
162    if (!entryIterator.hasNext()) {
163      return null;
164    }
165    Entry<E> entry = entryIterator.next();
166    entry = Multisets.immutableEntry(entry.getElement(), entry.getCount());
167    entryIterator.remove();
168    return entry;
169  }
170
171  @Override
172  public Entry<E> pollLastEntry() {
173    return delegate().pollLastEntry();
174  }
175
176  /**
177   * A sensible definition of {@link #pollLastEntry()} in terms of {@code
178   * descendingMultiset().entrySet().iterator()}.
179   *
180   * If you override {@link #descendingMultiset()} or {@link #entrySet()}, you may wish to override
181   * {@link #pollLastEntry()} to forward to this implementation.
182   */
183  protected Entry<E> standardPollLastEntry() {
184    Iterator<Entry<E>> entryIterator = descendingMultiset().entrySet().iterator();
185    if (!entryIterator.hasNext()) {
186      return null;
187    }
188    Entry<E> entry = entryIterator.next();
189    entry = Multisets.immutableEntry(entry.getElement(), entry.getCount());
190    entryIterator.remove();
191    return entry;
192  }
193
194  @Override
195  public SortedMultiset<E> headMultiset(E upperBound, BoundType boundType) {
196    return delegate().headMultiset(upperBound, boundType);
197  }
198
199  @Override
200  public SortedMultiset<E> subMultiset(
201      E lowerBound, BoundType lowerBoundType, E upperBound, BoundType upperBoundType) {
202    return delegate().subMultiset(lowerBound, lowerBoundType, upperBound, upperBoundType);
203  }
204
205  /**
206   * A sensible definition of {@link #subMultiset(Object, BoundType, Object, BoundType)} in terms
207   * of {@link #headMultiset(Object, BoundType) headMultiset} and
208   * {@link #tailMultiset(Object, BoundType) tailMultiset}.
209   *
210   * If you override either of these methods, you may wish to override
211   * {@link #subMultiset(Object, BoundType, Object, BoundType)} to forward to this implementation.
212   */
213  protected SortedMultiset<E> standardSubMultiset(
214      E lowerBound, BoundType lowerBoundType, E upperBound, BoundType upperBoundType) {
215    return tailMultiset(lowerBound, lowerBoundType).headMultiset(upperBound, upperBoundType);
216  }
217
218  @Override
219  public SortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType) {
220    return delegate().tailMultiset(lowerBound, boundType);
221  }
222}