NavigableMap.java revision 242e5bfd7e912be174c03a3c887369a6a9d6cbc2
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 36package java.util; 37 38// BEGIN android-note 39// removed link to collections framework docs 40// END android-note 41 42/** 43 * A {@link SortedMap} extended with navigation methods returning the 44 * closest matches for given search targets. Methods 45 * {@link #lowerEntry}, {@link #floorEntry}, {@link #ceilingEntry}, 46 * and {@link #higherEntry} return {@code Map.Entry} objects 47 * associated with keys respectively less than, less than or equal, 48 * greater than or equal, and greater than a given key, returning 49 * {@code null} if there is no such key. Similarly, methods 50 * {@link #lowerKey}, {@link #floorKey}, {@link #ceilingKey}, and 51 * {@link #higherKey} return only the associated keys. All of these 52 * methods are designed for locating, not traversing entries. 53 * 54 * <p>A {@code NavigableMap} may be accessed and traversed in either 55 * ascending or descending key order. The {@link #descendingMap} 56 * method returns a view of the map with the senses of all relational 57 * and directional methods inverted. The performance of ascending 58 * operations and views is likely to be faster than that of descending 59 * ones. Methods 60 * {@link #subMap(Object, boolean, Object, boolean) subMap(K, boolean, K, boolean)}, 61 * {@link #headMap(Object, boolean) headMap(K, boolean)}, and 62 * {@link #tailMap(Object, boolean) tailMap(K, boolean)} 63 * differ from the like-named {@code SortedMap} methods in accepting 64 * additional arguments describing whether lower and upper bounds are 65 * inclusive versus exclusive. Submaps of any {@code NavigableMap} 66 * must implement the {@code NavigableMap} interface. 67 * 68 * <p>This interface additionally defines methods {@link #firstEntry}, 69 * {@link #pollFirstEntry}, {@link #lastEntry}, and 70 * {@link #pollLastEntry} that return and/or remove the least and 71 * greatest mappings, if any exist, else returning {@code null}. 72 * 73 * <p>Implementations of entry-returning methods are expected to 74 * return {@code Map.Entry} pairs representing snapshots of mappings 75 * at the time they were produced, and thus generally do <em>not</em> 76 * support the optional {@code Entry.setValue} method. Note however 77 * that it is possible to change mappings in the associated map using 78 * method {@code put}. 79 * 80 * <p>Methods 81 * {@link #subMap(Object, Object) subMap(K, K)}, 82 * {@link #headMap(Object) headMap(K)}, and 83 * {@link #tailMap(Object) tailMap(K)} 84 * are specified to return {@code SortedMap} to allow existing 85 * implementations of {@code SortedMap} to be compatibly retrofitted to 86 * implement {@code NavigableMap}, but extensions and implementations 87 * of this interface are encouraged to override these methods to return 88 * {@code NavigableMap}. Similarly, 89 * {@link #keySet()} can be overridden to return {@link NavigableSet}. 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 */ 97public 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} 427