1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /*
26 * This file is available under and governed by the GNU General Public
27 * License version 2 only, as published by the Free Software Foundation.
28 * However, the following notice accompanied the original version of this
29 * file:
30 *
31 * Written by Doug Lea and Josh Bloch with assistance from members of JCP
32 * JSR-166 Expert Group and released to the public domain, as explained at
33 * http://creativecommons.org/publicdomain/zero/1.0/
34 */
35
36 package java.util;
37
38 /**
39 * A {@link SortedMap} extended with navigation methods returning the
40 * closest matches for given search targets. Methods
41 * {@link #lowerEntry}, {@link #floorEntry}, {@link #ceilingEntry},
42 * and {@link #higherEntry} return {@code Map.Entry} objects
43 * associated with keys respectively less than, less than or equal,
44 * greater than or equal, and greater than a given key, returning
45 * {@code null} if there is no such key. Similarly, methods
46 * {@link #lowerKey}, {@link #floorKey}, {@link #ceilingKey}, and
47 * {@link #higherKey} return only the associated keys. All of these
48 * methods are designed for locating, not traversing entries.
49 *
50 * <p>A {@code NavigableMap} may be accessed and traversed in either
51 * ascending or descending key order. The {@link #descendingMap}
52 * method returns a view of the map with the senses of all relational
53 * and directional methods inverted. The performance of ascending
54 * operations and views is likely to be faster than that of descending
55 * ones. Methods
56 * {@link #subMap(Object, boolean, Object, boolean) subMap(K, boolean, K, boolean)},
57 * {@link #headMap(Object, boolean) headMap(K, boolean)}, and
58 * {@link #tailMap(Object, boolean) tailMap(K, boolean)}
59 * differ from the like-named {@code SortedMap} methods in accepting
60 * additional arguments describing whether lower and upper bounds are
61 * inclusive versus exclusive. Submaps of any {@code NavigableMap}
62 * must implement the {@code NavigableMap} interface.
63 *
64 * <p>This interface additionally defines methods {@link #firstEntry},
65 * {@link #pollFirstEntry}, {@link #lastEntry}, and
66 * {@link #pollLastEntry} that return and/or remove the least and
67 * greatest mappings, if any exist, else returning {@code null}.
68 *
69 * <p>Implementations of entry-returning methods are expected to
70 * return {@code Map.Entry} pairs representing snapshots of mappings
71 * at the time they were produced, and thus generally do <em>not</em>
72 * support the optional {@code Entry.setValue} method. Note however
73 * that it is possible to change mappings in the associated map using
74 * method {@code put}.
75 *
76 * <p>Methods
77 * {@link #subMap(Object, Object) subMap(K, K)},
78 * {@link #headMap(Object) headMap(K)}, and
79 * {@link #tailMap(Object) tailMap(K)}
80 * are specified to return {@code SortedMap} to allow existing
81 * implementations of {@code SortedMap} to be compatibly retrofitted to
82 * implement {@code NavigableMap}, but extensions and implementations
83 * of this interface are encouraged to override these methods to return
84 * {@code NavigableMap}. Similarly,
85 * {@link #keySet()} can be overridden to return {@link NavigableSet}.
86 *
87 * <p>This interface is a member of the
88 * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
89 * Java Collections Framework</a>.
90 *
91 * @author Doug Lea
92 * @author Josh Bloch
93 * @param <K> the type of keys maintained by this map
94 * @param <V> the type of mapped values
95 * @since 1.6
96 */
97 public interface NavigableMap<K,V> extends SortedMap<K,V> {
98 /**
99 * Returns a key-value mapping associated with the greatest key
100 * strictly less than the given key, or {@code null} if there is
101 * no such key.
102 *
103 * @param key the key
104 * @return an entry with the greatest key less than {@code key},
105 * or {@code null} if there is no such key
106 * @throws ClassCastException if the specified key cannot be compared
107 * with the keys currently in the map
108 * @throws NullPointerException if the specified key is null
109 * and this map does not permit null keys
110 */
111 Map.Entry<K,V> lowerEntry(K key);
112
113 /**
114 * Returns the greatest key strictly less than the given key, or
115 * {@code null} if there is no such key.
116 *
117 * @param key the key
118 * @return the greatest key less than {@code key},
119 * or {@code null} if there is no such key
120 * @throws ClassCastException if the specified key cannot be compared
121 * with the keys currently in the map
122 * @throws NullPointerException if the specified key is null
123 * and this map does not permit null keys
124 */
125 K lowerKey(K key);
126
127 /**
128 * Returns a key-value mapping associated with the greatest key
129 * less than or equal to the given key, or {@code null} if there
130 * is no such key.
131 *
132 * @param key the key
133 * @return an entry with the greatest key less than or equal to
134 * {@code key}, or {@code null} if there is no such key
135 * @throws ClassCastException if the specified key cannot be compared
136 * with the keys currently in the map
137 * @throws NullPointerException if the specified key is null
138 * and this map does not permit null keys
139 */
140 Map.Entry<K,V> floorEntry(K key);
141
142 /**
143 * Returns the greatest key less than or equal to the given key,
144 * or {@code null} if there is no such key.
145 *
146 * @param key the key
147 * @return the greatest key less than or equal to {@code key},
148 * or {@code null} if there is no such key
149 * @throws ClassCastException if the specified key cannot be compared
150 * with the keys currently in the map
151 * @throws NullPointerException if the specified key is null
152 * and this map does not permit null keys
153 */
154 K floorKey(K key);
155
156 /**
157 * Returns a key-value mapping associated with the least key
158 * greater than or equal to the given key, or {@code null} if
159 * there is no such key.
160 *
161 * @param key the key
162 * @return an entry with the least key greater than or equal to
163 * {@code key}, or {@code null} if there is no such key
164 * @throws ClassCastException if the specified key cannot be compared
165 * with the keys currently in the map
166 * @throws NullPointerException if the specified key is null
167 * and this map does not permit null keys
168 */
169 Map.Entry<K,V> ceilingEntry(K key);
170
171 /**
172 * Returns the least key greater than or equal to the given key,
173 * or {@code null} if there is no such key.
174 *
175 * @param key the key
176 * @return the least key greater than or equal to {@code key},
177 * or {@code null} if there is no such key
178 * @throws ClassCastException if the specified key cannot be compared
179 * with the keys currently in the map
180 * @throws NullPointerException if the specified key is null
181 * and this map does not permit null keys
182 */
183 K ceilingKey(K key);
184
185 /**
186 * Returns a key-value mapping associated with the least key
187 * strictly greater than the given key, or {@code null} if there
188 * is no such key.
189 *
190 * @param key the key
191 * @return an entry with the least key greater than {@code key},
192 * or {@code null} if there is no such key
193 * @throws ClassCastException if the specified key cannot be compared
194 * with the keys currently in the map
195 * @throws NullPointerException if the specified key is null
196 * and this map does not permit null keys
197 */
198 Map.Entry<K,V> higherEntry(K key);
199
200 /**
201 * Returns the least key strictly greater than the given key, or
202 * {@code null} if there is no such key.
203 *
204 * @param key the key
205 * @return the least key greater than {@code key},
206 * or {@code null} if there is no such key
207 * @throws ClassCastException if the specified key cannot be compared
208 * with the keys currently in the map
209 * @throws NullPointerException if the specified key is null
210 * and this map does not permit null keys
211 */
212 K higherKey(K key);
213
214 /**
215 * Returns a key-value mapping associated with the least
216 * key in this map, or {@code null} if the map is empty.
217 *
218 * @return an entry with the least key,
219 * or {@code null} if this map is empty
220 */
221 Map.Entry<K,V> firstEntry();
222
223 /**
224 * Returns a key-value mapping associated with the greatest
225 * key in this map, or {@code null} if the map is empty.
226 *
227 * @return an entry with the greatest key,
228 * or {@code null} if this map is empty
229 */
230 Map.Entry<K,V> lastEntry();
231
232 /**
233 * Removes and returns a key-value mapping associated with
234 * the least key in this map, or {@code null} if the map is empty.
235 *
236 * @return the removed first entry of this map,
237 * or {@code null} if this map is empty
238 */
239 Map.Entry<K,V> pollFirstEntry();
240
241 /**
242 * Removes and returns a key-value mapping associated with
243 * the greatest key in this map, or {@code null} if the map is empty.
244 *
245 * @return the removed last entry of this map,
246 * or {@code null} if this map is empty
247 */
248 Map.Entry<K,V> pollLastEntry();
249
250 /**
251 * Returns a reverse order view of the mappings contained in this map.
252 * The descending map is backed by this map, so changes to the map are
253 * reflected in the descending map, and vice-versa. If either map is
254 * modified while an iteration over a collection view of either map
255 * is in progress (except through the iterator's own {@code remove}
256 * operation), the results of the iteration are undefined.
257 *
258 * <p>The returned map has an ordering equivalent to
259 * {@link Collections#reverseOrder(Comparator) Collections.reverseOrder}{@code (comparator())}.
260 * The expression {@code m.descendingMap().descendingMap()} returns a
261 * view of {@code m} essentially equivalent to {@code m}.
262 *
263 * @return a reverse order view of this map
264 */
265 NavigableMap<K,V> descendingMap();
266
267 /**
268 * Returns a {@link NavigableSet} view of the keys contained in this map.
269 * The set's iterator returns the keys in ascending order.
270 * The set is backed by the map, so changes to the map are reflected in
271 * the set, and vice-versa. If the map is modified while an iteration
272 * over the set is in progress (except through the iterator's own {@code
273 * remove} operation), the results of the iteration are undefined. The
274 * set supports element removal, which removes the corresponding mapping
275 * from the map, via the {@code Iterator.remove}, {@code Set.remove},
276 * {@code removeAll}, {@code retainAll}, and {@code clear} operations.
277 * It does not support the {@code add} or {@code addAll} operations.
278 *
279 * @return a navigable set view of the keys in this map
280 */
281 NavigableSet<K> navigableKeySet();
282
283 /**
284 * Returns a reverse order {@link NavigableSet} view of the keys contained in this map.
285 * The set's iterator returns the keys in descending order.
286 * The set is backed by the map, so changes to the map are reflected in
287 * the set, and vice-versa. If the map is modified while an iteration
288 * over the set is in progress (except through the iterator's own {@code
289 * remove} operation), the results of the iteration are undefined. The
290 * set supports element removal, which removes the corresponding mapping
291 * from the map, via the {@code Iterator.remove}, {@code Set.remove},
292 * {@code removeAll}, {@code retainAll}, and {@code clear} operations.
293 * It does not support the {@code add} or {@code addAll} operations.
294 *
295 * @return a reverse order navigable set view of the keys in this map
296 */
297 NavigableSet<K> descendingKeySet();
298
299 /**
300 * Returns a view of the portion of this map whose keys range from
301 * {@code fromKey} to {@code toKey}. If {@code fromKey} and
302 * {@code toKey} are equal, the returned map is empty unless
303 * {@code fromInclusive} and {@code toInclusive} are both true. The
304 * returned map is backed by this map, so changes in the returned map are
305 * reflected in this map, and vice-versa. The returned map supports all
306 * optional map operations that this map supports.
307 *
308 * <p>The returned map will throw an {@code IllegalArgumentException}
309 * on an attempt to insert a key outside of its range, or to construct a
310 * submap either of whose endpoints lie outside its range.
311 *
312 * @param fromKey low endpoint of the keys in the returned map
313 * @param fromInclusive {@code true} if the low endpoint
314 * is to be included in the returned view
315 * @param toKey high endpoint of the keys in the returned map
316 * @param toInclusive {@code true} if the high endpoint
317 * is to be included in the returned view
318 * @return a view of the portion of this map whose keys range from
319 * {@code fromKey} to {@code toKey}
320 * @throws ClassCastException if {@code fromKey} and {@code toKey}
321 * cannot be compared to one another using this map's comparator
322 * (or, if the map has no comparator, using natural ordering).
323 * Implementations may, but are not required to, throw this
324 * exception if {@code fromKey} or {@code toKey}
325 * cannot be compared to keys currently in the map.
326 * @throws NullPointerException if {@code fromKey} or {@code toKey}
327 * is null and this map does not permit null keys
328 * @throws IllegalArgumentException if {@code fromKey} is greater than
329 * {@code toKey}; or if this map itself has a restricted
330 * range, and {@code fromKey} or {@code toKey} lies
331 * outside the bounds of the range
332 */
333 NavigableMap<K,V> subMap(K fromKey, boolean fromInclusive,
334 K toKey, boolean toInclusive);
335
336 /**
337 * Returns a view of the portion of this map whose keys are less than (or
338 * equal to, if {@code inclusive} is true) {@code toKey}. The returned
339 * map is backed by this map, so changes in the returned map are reflected
340 * in this map, and vice-versa. The returned map supports all optional
341 * map operations that this map supports.
342 *
343 * <p>The returned map will throw an {@code IllegalArgumentException}
344 * on an attempt to insert a key outside its range.
345 *
346 * @param toKey high endpoint of the keys in the returned map
347 * @param inclusive {@code true} if the high endpoint
348 * is to be included in the returned view
349 * @return a view of the portion of this map whose keys are less than
350 * (or equal to, if {@code inclusive} is true) {@code toKey}
351 * @throws ClassCastException if {@code toKey} is not compatible
352 * with this map's comparator (or, if the map has no comparator,
353 * if {@code toKey} does not implement {@link Comparable}).
354 * Implementations may, but are not required to, throw this
355 * exception if {@code toKey} cannot be compared to keys
356 * currently in the map.
357 * @throws NullPointerException if {@code toKey} is null
358 * and this map does not permit null keys
359 * @throws IllegalArgumentException if this map itself has a
360 * restricted range, and {@code toKey} lies outside the
361 * bounds of the range
362 */
363 NavigableMap<K,V> headMap(K toKey, boolean inclusive);
364
365 /**
366 * Returns a view of the portion of this map whose keys are greater than (or
367 * equal to, if {@code inclusive} is true) {@code fromKey}. The returned
368 * map is backed by this map, so changes in the returned map are reflected
369 * in this map, and vice-versa. The returned map supports all optional
370 * map operations that this map supports.
371 *
372 * <p>The returned map will throw an {@code IllegalArgumentException}
373 * on an attempt to insert a key outside its range.
374 *
375 * @param fromKey low endpoint of the keys in the returned map
376 * @param inclusive {@code true} if the low endpoint
377 * is to be included in the returned view
378 * @return a view of the portion of this map whose keys are greater than
379 * (or equal to, if {@code inclusive} is true) {@code fromKey}
380 * @throws ClassCastException if {@code fromKey} is not compatible
381 * with this map's comparator (or, if the map has no comparator,
382 * if {@code fromKey} does not implement {@link Comparable}).
383 * Implementations may, but are not required to, throw this
384 * exception if {@code fromKey} cannot be compared to keys
385 * currently in the map.
386 * @throws NullPointerException if {@code fromKey} is null
387 * and this map does not permit null keys
388 * @throws IllegalArgumentException if this map itself has a
389 * restricted range, and {@code fromKey} lies outside the
390 * bounds of the range
391 */
392 NavigableMap<K,V> tailMap(K fromKey, boolean inclusive);
393
394 /**
395 * {@inheritDoc}
396 *
397 * <p>Equivalent to {@code subMap(fromKey, true, toKey, false)}.
398 *
399 * @throws ClassCastException {@inheritDoc}
400 * @throws NullPointerException {@inheritDoc}
401 * @throws IllegalArgumentException {@inheritDoc}
402 */
403 SortedMap<K,V> subMap(K fromKey, K toKey);
404
405 /**
406 * {@inheritDoc}
407 *
408 * <p>Equivalent to {@code headMap(toKey, false)}.
409 *
410 * @throws ClassCastException {@inheritDoc}
411 * @throws NullPointerException {@inheritDoc}
412 * @throws IllegalArgumentException {@inheritDoc}
413 */
414 SortedMap<K,V> headMap(K toKey);
415
416 /**
417 * {@inheritDoc}
418 *
419 * <p>Equivalent to {@code tailMap(fromKey, true)}.
420 *
421 * @throws ClassCastException {@inheritDoc}
422 * @throws NullPointerException {@inheritDoc}
423 * @throws IllegalArgumentException {@inheritDoc}
424 */
425 SortedMap<K,V> tailMap(K fromKey);
426 }