001/*
002 * Copyright (C) 2007 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.Beta;
020import com.google.common.annotations.GwtCompatible;
021
022import java.util.Comparator;
023import java.util.Iterator;
024import java.util.NoSuchElementException;
025import java.util.SortedMap;
026
027import javax.annotation.Nullable;
028
029/**
030 * A sorted map which forwards all its method calls to another sorted map.
031 * Subclasses should override one or more methods to modify the behavior of
032 * the backing sorted map as desired per the <a
033 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
034 *
035 * <p><i>Warning:</i> The methods of {@code ForwardingSortedMap} forward
036 * <i>indiscriminately</i> to the methods of the delegate. For example,
037 * overriding {@link #put} alone <i>will not</i> change the behavior of {@link
038 * #putAll}, which can lead to unexpected behavior. In this case, you should
039 * override {@code putAll} as well, either providing your own implementation, or
040 * delegating to the provided {@code standardPutAll} method.
041 *
042 * <p>Each of the {@code standard} methods, where appropriate, use the
043 * comparator of the map to test equality for both keys and values, unlike
044 * {@code ForwardingMap}.
045 *
046 * <p>The {@code standard} methods and the collection views they return are not
047 * guaranteed to be thread-safe, even when all of the methods that they depend
048 * on are thread-safe.
049 *
050 * @author Mike Bostock
051 * @author Louis Wasserman
052 * @since 2.0 (imported from Google Collections Library)
053 */
054@GwtCompatible
055public abstract class ForwardingSortedMap<K, V> extends ForwardingMap<K, V>
056    implements SortedMap<K, V> {
057  // TODO(user): identify places where thread safety is actually lost
058
059  /** Constructor for use by subclasses. */
060  protected ForwardingSortedMap() {}
061
062  @Override protected abstract SortedMap<K, V> delegate();
063
064  @Override
065  public Comparator<? super K> comparator() {
066    return delegate().comparator();
067  }
068
069  @Override
070  public K firstKey() {
071    return delegate().firstKey();
072  }
073
074  @Override
075  public SortedMap<K, V> headMap(K toKey) {
076    return delegate().headMap(toKey);
077  }
078
079  @Override
080  public K lastKey() {
081    return delegate().lastKey();
082  }
083
084  @Override
085  public SortedMap<K, V> subMap(K fromKey, K toKey) {
086    return delegate().subMap(fromKey, toKey);
087  }
088
089  @Override
090  public SortedMap<K, V> tailMap(K fromKey) {
091    return delegate().tailMap(fromKey);
092  }
093
094  // unsafe, but worst case is a CCE is thrown, which callers will be expecting
095  @SuppressWarnings("unchecked")
096  private int unsafeCompare(Object k1, Object k2) {
097    Comparator<? super K> comparator = comparator();
098    if (comparator == null) {
099      return ((Comparable<Object>) k1).compareTo(k2);
100    } else {
101      return ((Comparator<Object>) comparator).compare(k1, k2);
102    }
103  }
104
105  /**
106   * A sensible definition of {@link #containsKey} in terms of the {@code
107   * firstKey()} method of {@link #tailMap}. If you override {@link #tailMap},
108   * you may wish to override {@link #containsKey} to forward to this
109   * implementation.
110   *
111   * @since 7.0
112   */
113  @Override @Beta protected boolean standardContainsKey(@Nullable Object key) {
114    try {
115      // any CCE will be caught
116      @SuppressWarnings("unchecked")
117      SortedMap<Object, V> self = (SortedMap<Object, V>) this;
118      Object ceilingKey = self.tailMap(key).firstKey();
119      return unsafeCompare(ceilingKey, key) == 0;
120    } catch (ClassCastException e) {
121      return false;
122    } catch (NoSuchElementException e) {
123      return false;
124    } catch (NullPointerException e) {
125      return false;
126    }
127  }
128
129  /**
130   * A sensible definition of {@link #remove} in terms of the {@code
131   * iterator()} of the {@code entrySet()} of {@link #tailMap}. If you override
132   * {@link #tailMap}, you may wish to override {@link #remove} to forward
133   * to this implementation.
134   *
135   * @since 7.0
136   */
137  @Override @Beta protected V standardRemove(@Nullable Object key) {
138    try {
139      // any CCE will be caught
140      @SuppressWarnings("unchecked")
141      SortedMap<Object, V> self = (SortedMap<Object, V>) this;
142      Iterator<Entry<Object, V>> entryIterator =
143          self.tailMap(key).entrySet().iterator();
144      if (entryIterator.hasNext()) {
145        Entry<Object, V> ceilingEntry = entryIterator.next();
146        if (unsafeCompare(ceilingEntry.getKey(), key) == 0) {
147          V value = ceilingEntry.getValue();
148          entryIterator.remove();
149          return value;
150        }
151      }
152    } catch (ClassCastException e) {
153      return null;
154    } catch (NullPointerException e) {
155      return null;
156    }
157    return null;
158  }
159
160  /**
161   * A sensible default implementation of {@link #subMap(Object, Object)} in
162   * terms of {@link #headMap(Object)} and {@link #tailMap(Object)}. In some
163   * situations, you may wish to override {@link #subMap(Object, Object)} to
164   * forward to this implementation.
165   *
166   * @since 7.0
167   */
168  @Beta protected SortedMap<K, V> standardSubMap(K fromKey, K toKey) {
169    return tailMap(fromKey).headMap(toKey);
170  }
171}