1 /*
2 * Copyright (c) 1998, 2006, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
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24 */
25
26 package java.util;
27
28 /**
29 * A {@link Map} that further provides a <i>total ordering</i> on its keys.
30 * The map is ordered according to the {@linkplain Comparable natural
31 * ordering} of its keys, or by a {@link Comparator} typically
32 * provided at sorted map creation time. This order is reflected when
33 * iterating over the sorted map's collection views (returned by the
34 * <tt>entrySet</tt>, <tt>keySet</tt> and <tt>values</tt> methods).
35 * Several additional operations are provided to take advantage of the
36 * ordering. (This interface is the map analogue of {@link
37 * SortedSet}.)
38 *
39 * <p>All keys inserted into a sorted map must implement the <tt>Comparable</tt>
40 * interface (or be accepted by the specified comparator). Furthermore, all
41 * such keys must be <i>mutually comparable</i>: <tt>k1.compareTo(k2)</tt> (or
42 * <tt>comparator.compare(k1, k2)</tt>) must not throw a
43 * <tt>ClassCastException</tt> for any keys <tt>k1</tt> and <tt>k2</tt> in
44 * the sorted map. Attempts to violate this restriction will cause the
45 * offending method or constructor invocation to throw a
46 * <tt>ClassCastException</tt>.
47 *
48 * <p>Note that the ordering maintained by a sorted map (whether or not an
49 * explicit comparator is provided) must be <i>consistent with equals</i> if
50 * the sorted map is to correctly implement the <tt>Map</tt> interface. (See
51 * the <tt>Comparable</tt> interface or <tt>Comparator</tt> interface for a
52 * precise definition of <i>consistent with equals</i>.) This is so because
53 * the <tt>Map</tt> interface is defined in terms of the <tt>equals</tt>
54 * operation, but a sorted map performs all key comparisons using its
55 * <tt>compareTo</tt> (or <tt>compare</tt>) method, so two keys that are
56 * deemed equal by this method are, from the standpoint of the sorted map,
57 * equal. The behavior of a tree map <i>is</i> well-defined even if its
58 * ordering is inconsistent with equals; it just fails to obey the general
59 * contract of the <tt>Map</tt> interface.
60 *
61 * <p>All general-purpose sorted map implementation classes should
62 * provide four "standard" constructors: 1) A void (no arguments)
63 * constructor, which creates an empty sorted map sorted according to
64 * the natural ordering of its keys. 2) A constructor with a
65 * single argument of type <tt>Comparator</tt>, which creates an empty
66 * sorted map sorted according to the specified comparator. 3) A
67 * constructor with a single argument of type <tt>Map</tt>, which
68 * creates a new map with the same key-value mappings as its argument,
69 * sorted according to the keys' natural ordering. 4) A constructor
70 * with a single argument of type <tt>SortedMap</tt>,
71 * which creates a new sorted map with the same key-value mappings and
72 * the same ordering as the input sorted map. There is no way to
73 * enforce this recommendation, as interfaces cannot contain
74 * constructors.
75 *
76 * <p>Note: several methods return submaps with restricted key ranges.
77 * Such ranges are <i>half-open</i>, that is, they include their low
78 * endpoint but not their high endpoint (where applicable). If you need a
79 * <i>closed range</i> (which includes both endpoints), and the key type
80 * allows for calculation of the successor of a given key, merely request
81 * the subrange from <tt>lowEndpoint</tt> to
82 * <tt>successor(highEndpoint)</tt>. For example, suppose that <tt>m</tt>
83 * is a map whose keys are strings. The following idiom obtains a view
84 * containing all of the key-value mappings in <tt>m</tt> whose keys are
85 * between <tt>low</tt> and <tt>high</tt>, inclusive:<pre>
86 * SortedMap<String, V> sub = m.subMap(low, high+"\0");</pre>
87 *
88 * A similar technique can be used to generate an <i>open range</i>
89 * (which contains neither endpoint). The following idiom obtains a
90 * view containing all of the key-value mappings in <tt>m</tt> whose keys
91 * are between <tt>low</tt> and <tt>high</tt>, exclusive:<pre>
92 * SortedMap<String, V> sub = m.subMap(low+"\0", high);</pre>
93 *
94 * <p>This interface is a member of the
95 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
96 * Java Collections Framework</a>.
97 *
98 * @param <K> the type of keys maintained by this map
99 * @param <V> the type of mapped values
100 *
101 * @author Josh Bloch
102 * @see Map
103 * @see TreeMap
104 * @see SortedSet
105 * @see Comparator
106 * @see Comparable
107 * @see Collection
108 * @see ClassCastException
109 * @since 1.2
110 */
111
112 public interface SortedMap<K,V> extends Map<K,V> {
113 /**
114 * Returns the comparator used to order the keys in this map, or
115 * <tt>null</tt> if this map uses the {@linkplain Comparable
116 * natural ordering} of its keys.
117 *
118 * @return the comparator used to order the keys in this map,
119 * or <tt>null</tt> if this map uses the natural ordering
120 * of its keys
121 */
122 Comparator<? super K> comparator();
123
124 /**
125 * Returns a view of the portion of this map whose keys range from
126 * <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive. (If
127 * <tt>fromKey</tt> and <tt>toKey</tt> are equal, the returned map
128 * is empty.) The returned map is backed by this map, so changes
129 * in the returned map are reflected in this map, and vice-versa.
130 * The returned map supports all optional map operations that this
131 * map supports.
132 *
133 * <p>The returned map will throw an <tt>IllegalArgumentException</tt>
134 * on an attempt to insert a key outside its range.
135 *
136 * @param fromKey low endpoint (inclusive) of the keys in the returned map
137 * @param toKey high endpoint (exclusive) of the keys in the returned map
138 * @return a view of the portion of this map whose keys range from
139 * <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive
140 * @throws ClassCastException if <tt>fromKey</tt> and <tt>toKey</tt>
141 * cannot be compared to one another using this map's comparator
142 * (or, if the map has no comparator, using natural ordering).
143 * Implementations may, but are not required to, throw this
144 * exception if <tt>fromKey</tt> or <tt>toKey</tt>
145 * cannot be compared to keys currently in the map.
146 * @throws NullPointerException if <tt>fromKey</tt> or <tt>toKey</tt>
147 * is null and this map does not permit null keys
148 * @throws IllegalArgumentException if <tt>fromKey</tt> is greater than
149 * <tt>toKey</tt>; or if this map itself has a restricted
150 * range, and <tt>fromKey</tt> or <tt>toKey</tt> lies
151 * outside the bounds of the range
152 */
153 SortedMap<K,V> subMap(K fromKey, K toKey);
154
155 /**
156 * Returns a view of the portion of this map whose keys are
157 * strictly less than <tt>toKey</tt>. The returned map is backed
158 * by this map, so changes in the returned map are reflected in
159 * this map, and vice-versa. The returned map supports all
160 * optional map operations that this map supports.
161 *
162 * <p>The returned map will throw an <tt>IllegalArgumentException</tt>
163 * on an attempt to insert a key outside its range.
164 *
165 * @param toKey high endpoint (exclusive) of the keys in the returned map
166 * @return a view of the portion of this map whose keys are strictly
167 * less than <tt>toKey</tt>
168 * @throws ClassCastException if <tt>toKey</tt> is not compatible
169 * with this map's comparator (or, if the map has no comparator,
170 * if <tt>toKey</tt> does not implement {@link Comparable}).
171 * Implementations may, but are not required to, throw this
172 * exception if <tt>toKey</tt> cannot be compared to keys
173 * currently in the map.
174 * @throws NullPointerException if <tt>toKey</tt> is null and
175 * this map does not permit null keys
176 * @throws IllegalArgumentException if this map itself has a
177 * restricted range, and <tt>toKey</tt> lies outside the
178 * bounds of the range
179 */
180 SortedMap<K,V> headMap(K toKey);
181
182 /**
183 * Returns a view of the portion of this map whose keys are
184 * greater than or equal to <tt>fromKey</tt>. The returned map is
185 * backed by this map, so changes in the returned map are
186 * reflected in this map, and vice-versa. The returned map
187 * supports all optional map operations that this map supports.
188 *
189 * <p>The returned map will throw an <tt>IllegalArgumentException</tt>
190 * on an attempt to insert a key outside its range.
191 *
192 * @param fromKey low endpoint (inclusive) of the keys in the returned map
193 * @return a view of the portion of this map whose keys are greater
194 * than or equal to <tt>fromKey</tt>
195 * @throws ClassCastException if <tt>fromKey</tt> is not compatible
196 * with this map's comparator (or, if the map has no comparator,
197 * if <tt>fromKey</tt> does not implement {@link Comparable}).
198 * Implementations may, but are not required to, throw this
199 * exception if <tt>fromKey</tt> cannot be compared to keys
200 * currently in the map.
201 * @throws NullPointerException if <tt>fromKey</tt> is null and
202 * this map does not permit null keys
203 * @throws IllegalArgumentException if this map itself has a
204 * restricted range, and <tt>fromKey</tt> lies outside the
205 * bounds of the range
206 */
207 SortedMap<K,V> tailMap(K fromKey);
208
209 /**
210 * Returns the first (lowest) key currently in this map.
211 *
212 * @return the first (lowest) key currently in this map
213 * @throws NoSuchElementException if this map is empty
214 */
215 K firstKey();
216
217 /**
218 * Returns the last (highest) key currently in this map.
219 *
220 * @return the last (highest) key currently in this map
221 * @throws NoSuchElementException if this map is empty
222 */
223 K lastKey();
224
225 /**
226 * Returns a {@link Set} view of the keys contained in this map.
227 * The set's iterator returns the keys in ascending order.
228 * The set is backed by the map, so changes to the map are
229 * reflected in the set, and vice-versa. If the map is modified
230 * while an iteration over the set is in progress (except through
231 * the iterator's own <tt>remove</tt> operation), the results of
232 * the iteration are undefined. The set supports element removal,
233 * which removes the corresponding mapping from the map, via the
234 * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
235 * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
236 * operations. It does not support the <tt>add</tt> or <tt>addAll</tt>
237 * operations.
238 *
239 * @return a set view of the keys contained in this map, sorted in
240 * ascending order
241 */
242 Set<K> keySet();
243
244 /**
245 * Returns a {@link Collection} view of the values contained in this map.
246 * The collection's iterator returns the values in ascending order
247 * of the corresponding keys.
248 * The collection is backed by the map, so changes to the map are
249 * reflected in the collection, and vice-versa. If the map is
250 * modified while an iteration over the collection is in progress
251 * (except through the iterator's own <tt>remove</tt> operation),
252 * the results of the iteration are undefined. The collection
253 * supports element removal, which removes the corresponding
254 * mapping from the map, via the <tt>Iterator.remove</tt>,
255 * <tt>Collection.remove</tt>, <tt>removeAll</tt>,
256 * <tt>retainAll</tt> and <tt>clear</tt> operations. It does not
257 * support the <tt>add</tt> or <tt>addAll</tt> operations.
258 *
259 * @return a collection view of the values contained in this map,
260 * sorted in ascending key order
261 */
262 Collection<V> values();
263
264 /**
265 * Returns a {@link Set} view of the mappings contained in this map.
266 * The set's iterator returns the entries in ascending key order.
267 * The set is backed by the map, so changes to the map are
268 * reflected in the set, and vice-versa. If the map is modified
269 * while an iteration over the set is in progress (except through
270 * the iterator's own <tt>remove</tt> operation, or through the
271 * <tt>setValue</tt> operation on a map entry returned by the
272 * iterator) the results of the iteration are undefined. The set
273 * supports element removal, which removes the corresponding
274 * mapping from the map, via the <tt>Iterator.remove</tt>,
275 * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
276 * <tt>clear</tt> operations. It does not support the
277 * <tt>add</tt> or <tt>addAll</tt> operations.
278 *
279 * @return a set view of the mappings contained in this map,
280 * sorted in ascending key order
281 */
282 Set<Map.Entry<K, V>> entrySet();
283 }