001 /*
002 * Copyright (C) 2007 Google Inc.
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 public Comparator<? super K> comparator() {
065 return delegate().comparator();
066 }
067
068 public K firstKey() {
069 return delegate().firstKey();
070 }
071
072 public SortedMap<K, V> headMap(K toKey) {
073 return delegate().headMap(toKey);
074 }
075
076 public K lastKey() {
077 return delegate().lastKey();
078 }
079
080 public SortedMap<K, V> subMap(K fromKey, K toKey) {
081 return delegate().subMap(fromKey, toKey);
082 }
083
084 public SortedMap<K, V> tailMap(K fromKey) {
085 return delegate().tailMap(fromKey);
086 }
087
088 // unsafe, but worst case is a CCE is thrown, which callers will be expecting
089 @SuppressWarnings("unchecked")
090 private int unsafeCompare(Object k1, Object k2) {
091 Comparator<? super K> comparator = comparator();
092 if (comparator == null) {
093 return ((Comparable) k1).compareTo(k2);
094 } else {
095 return ((Comparator) comparator).compare(k1, k2);
096 }
097 }
098
099 /**
100 * A sensible definition of {@link #containsKey} in terms of the {@code
101 * firstKey()} method of {@link #tailMap}. If you override {@link #tailMap},
102 * you may wish to override {@link #containsKey} to forward to this
103 * implementation.
104 *
105 * @since 7
106 */
107 @Override @Beta protected boolean standardContainsKey(@Nullable Object key) {
108 try {
109 // any CCE will be caught
110 @SuppressWarnings("unchecked")
111 SortedMap<Object, V> self = (SortedMap) this;
112 Object ceilingKey = self.tailMap(key).firstKey();
113 return unsafeCompare(ceilingKey, key) == 0;
114 } catch (ClassCastException e) {
115 return false;
116 } catch (NoSuchElementException e) {
117 return false;
118 } catch (NullPointerException e) {
119 return false;
120 }
121 }
122
123 /**
124 * A sensible definition of {@link #remove} in terms of the {@code
125 * iterator()} of the {@code entrySet()} of {@link #tailMap}. If you override
126 * {@link #tailMap}, you may wish to override {@link #remove} to forward
127 * to this implementation.
128 *
129 * @since 7
130 */
131 @Override @Beta protected V standardRemove(@Nullable Object key) {
132 try {
133 // any CCE will be caught
134 @SuppressWarnings("unchecked")
135 SortedMap<Object, V> self = (SortedMap) this;
136 Iterator<Entry<Object, V>> entryIterator =
137 self.tailMap(key).entrySet().iterator();
138 if (entryIterator.hasNext()) {
139 Entry<Object, V> ceilingEntry = entryIterator.next();
140 if (unsafeCompare(ceilingEntry.getKey(), key) == 0) {
141 V value = ceilingEntry.getValue();
142 entryIterator.remove();
143 return value;
144 }
145 }
146 } catch (ClassCastException e) {
147 return null;
148 } catch (NullPointerException e) {
149 return null;
150 }
151 return null;
152 }
153
154 /**
155 * A sensible default implementation of {@link #subMap(Object, Object)} in
156 * terms of {@link #headMap(Object)} and {@link #tailMap(Object)}. In some
157 * situations, you may wish to override {@link #subMap(Object, Object)} to
158 * forward to this implementation.
159 *
160 * @since 7
161 */
162 @Beta protected SortedMap<K, V> standardSubMap(K fromKey, K toKey) {
163 return tailMap(fromKey).headMap(toKey);
164 }
165 }