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
017 package com.google.common.collect;
018
019 import com.google.common.annotations.Beta;
020 import com.google.common.annotations.GwtCompatible;
021
022 import java.util.Comparator;
023 import java.util.Iterator;
024 import java.util.NoSuchElementException;
025 import java.util.SortedMap;
026
027 import 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><em>Warning</em>: The methods of {@code ForwardingSortedMap} forward
036 * <em>indiscriminately</em> to the methods of the delegate. For example,
037 * overriding {@link #put} alone <em>will not</em> 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 (imported from Google Collections Library)
053 */
054 @GwtCompatible
055 public 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
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
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
167 */
168 @Beta protected SortedMap<K, V> standardSubMap(K fromKey, K toKey) {
169 return tailMap(fromKey).headMap(toKey);
170 }
171 }