NavigableMap.java revision 51b1b6997fd3f980076b8081f7f1165ccc2a4008
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/** 39 * A {@link SortedMap} extended with navigation methods returning the 40 * closest matches for given search targets. Methods 41 * {@code lowerEntry}, {@code floorEntry}, {@code ceilingEntry}, 42 * and {@code 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 * {@code lowerKey}, {@code floorKey}, {@code ceilingKey}, and 47 * {@code 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 {@code 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 {@code subMap}, {@code headMap}, 56 * and {@code tailMap} differ from the like-named {@code 57 * SortedMap} methods in accepting additional arguments describing 58 * whether lower and upper bounds are inclusive versus exclusive. 59 * Submaps of any {@code NavigableMap} must implement the {@code 60 * NavigableMap} interface. 61 * 62 * <p>This interface additionally defines methods {@code firstEntry}, 63 * {@code pollFirstEntry}, {@code lastEntry}, and 64 * {@code pollLastEntry} that return and/or remove the least and 65 * greatest mappings, if any exist, else returning {@code null}. 66 * 67 * <p>Implementations of entry-returning methods are expected to 68 * return {@code Map.Entry} pairs representing snapshots of mappings 69 * at the time they were produced, and thus generally do <em>not</em> 70 * support the optional {@code Entry.setValue} method. Note however 71 * that it is possible to change mappings in the associated map using 72 * method {@code put}. 73 * 74 * <p>Methods 75 * {@link #subMap(Object, Object) subMap(K, K)}, 76 * {@link #headMap(Object) headMap(K)}, and 77 * {@link #tailMap(Object) tailMap(K)} 78 * are specified to return {@code SortedMap} to allow existing 79 * implementations of {@code SortedMap} to be compatibly retrofitted to 80 * implement {@code NavigableMap}, but extensions and implementations 81 * of this interface are encouraged to override these methods to return 82 * {@code NavigableMap}. Similarly, 83 * {@link #keySet()} can be overriden to return {@code NavigableSet}. 84 * 85 * <p>This interface is a member of the 86 * <a href="{@docRoot}/../technotes/guides/collections/index.html"> 87 * Java Collections Framework</a>. 88 * 89 * @author Doug Lea 90 * @author Josh Bloch 91 * @param <K> the type of keys maintained by this map 92 * @param <V> the type of mapped values 93 * @since 1.6 94 */ 95public interface NavigableMap<K,V> extends SortedMap<K,V> { 96 /** 97 * Returns a key-value mapping associated with the greatest key 98 * strictly less than the given key, or {@code null} if there is 99 * no such key. 100 * 101 * @param key the key 102 * @return an entry with the greatest key less than {@code key}, 103 * or {@code null} if there is no such key 104 * @throws ClassCastException if the specified key cannot be compared 105 * with the keys currently in the map 106 * @throws NullPointerException if the specified key is null 107 * and this map does not permit null keys 108 */ 109 Map.Entry<K,V> lowerEntry(K key); 110 111 /** 112 * Returns the greatest key strictly less than the given key, or 113 * {@code null} if there is no such key. 114 * 115 * @param key the key 116 * @return the greatest key less than {@code key}, 117 * or {@code null} if there is no such key 118 * @throws ClassCastException if the specified key cannot be compared 119 * with the keys currently in the map 120 * @throws NullPointerException if the specified key is null 121 * and this map does not permit null keys 122 */ 123 K lowerKey(K key); 124 125 /** 126 * Returns a key-value mapping associated with the greatest key 127 * less than or equal to the given key, or {@code null} if there 128 * is no such key. 129 * 130 * @param key the key 131 * @return an entry with the greatest key less than or equal to 132 * {@code key}, or {@code null} if there is no such key 133 * @throws ClassCastException if the specified key cannot be compared 134 * with the keys currently in the map 135 * @throws NullPointerException if the specified key is null 136 * and this map does not permit null keys 137 */ 138 Map.Entry<K,V> floorEntry(K key); 139 140 /** 141 * Returns the greatest key less than or equal to the given key, 142 * or {@code null} if there is no such key. 143 * 144 * @param key the key 145 * @return the greatest key less than or equal to {@code key}, 146 * or {@code null} if there is no such key 147 * @throws ClassCastException if the specified key cannot be compared 148 * with the keys currently in the map 149 * @throws NullPointerException if the specified key is null 150 * and this map does not permit null keys 151 */ 152 K floorKey(K key); 153 154 /** 155 * Returns a key-value mapping associated with the least key 156 * greater than or equal to the given key, or {@code null} if 157 * there is no such key. 158 * 159 * @param key the key 160 * @return an entry with the least key greater than or equal to 161 * {@code key}, or {@code null} if there is no such key 162 * @throws ClassCastException if the specified key cannot be compared 163 * with the keys currently in the map 164 * @throws NullPointerException if the specified key is null 165 * and this map does not permit null keys 166 */ 167 Map.Entry<K,V> ceilingEntry(K key); 168 169 /** 170 * Returns the least key greater than or equal to the given key, 171 * or {@code null} if there is no such key. 172 * 173 * @param key the key 174 * @return the least key greater than or equal to {@code key}, 175 * or {@code null} if there is no such key 176 * @throws ClassCastException if the specified key cannot be compared 177 * with the keys currently in the map 178 * @throws NullPointerException if the specified key is null 179 * and this map does not permit null keys 180 */ 181 K ceilingKey(K key); 182 183 /** 184 * Returns a key-value mapping associated with the least key 185 * strictly greater than the given key, or {@code null} if there 186 * is no such key. 187 * 188 * @param key the key 189 * @return an entry with the least key greater than {@code key}, 190 * or {@code null} if there is no such key 191 * @throws ClassCastException if the specified key cannot be compared 192 * with the keys currently in the map 193 * @throws NullPointerException if the specified key is null 194 * and this map does not permit null keys 195 */ 196 Map.Entry<K,V> higherEntry(K key); 197 198 /** 199 * Returns the least key strictly greater than the given key, or 200 * {@code null} if there is no such key. 201 * 202 * @param key the key 203 * @return the least key greater than {@code key}, 204 * or {@code null} if there is no such key 205 * @throws ClassCastException if the specified key cannot be compared 206 * with the keys currently in the map 207 * @throws NullPointerException if the specified key is null 208 * and this map does not permit null keys 209 */ 210 K higherKey(K key); 211 212 /** 213 * Returns a key-value mapping associated with the least 214 * key in this map, or {@code null} if the map is empty. 215 * 216 * @return an entry with the least key, 217 * or {@code null} if this map is empty 218 */ 219 Map.Entry<K,V> firstEntry(); 220 221 /** 222 * Returns a key-value mapping associated with the greatest 223 * key in this map, or {@code null} if the map is empty. 224 * 225 * @return an entry with the greatest key, 226 * or {@code null} if this map is empty 227 */ 228 Map.Entry<K,V> lastEntry(); 229 230 /** 231 * Removes and returns a key-value mapping associated with 232 * the least key in this map, or {@code null} if the map is empty. 233 * 234 * @return the removed first entry of this map, 235 * or {@code null} if this map is empty 236 */ 237 Map.Entry<K,V> pollFirstEntry(); 238 239 /** 240 * Removes and returns a key-value mapping associated with 241 * the greatest key in this map, or {@code null} if the map is empty. 242 * 243 * @return the removed last entry of this map, 244 * or {@code null} if this map is empty 245 */ 246 Map.Entry<K,V> pollLastEntry(); 247 248 /** 249 * Returns a reverse order view of the mappings contained in this map. 250 * The descending map is backed by this map, so changes to the map are 251 * reflected in the descending map, and vice-versa. If either map is 252 * modified while an iteration over a collection view of either map 253 * is in progress (except through the iterator's own {@code remove} 254 * operation), the results of the iteration are undefined. 255 * 256 * <p>The returned map has an ordering equivalent to 257 * <tt>{@link Collections#reverseOrder(Comparator) Collections.reverseOrder}(comparator())</tt>. 258 * The expression {@code m.descendingMap().descendingMap()} returns a 259 * view of {@code m} essentially equivalent to {@code m}. 260 * 261 * @return a reverse order view of this map 262 */ 263 NavigableMap<K,V> descendingMap(); 264 265 /** 266 * Returns a {@link NavigableSet} view of the keys contained in this map. 267 * The set's iterator returns the keys in ascending order. 268 * The set is backed by the map, so changes to the map are reflected in 269 * the set, and vice-versa. If the map is modified while an iteration 270 * over the set is in progress (except through the iterator's own {@code 271 * remove} operation), the results of the iteration are undefined. The 272 * set supports element removal, which removes the corresponding mapping 273 * from the map, via the {@code Iterator.remove}, {@code Set.remove}, 274 * {@code removeAll}, {@code retainAll}, and {@code clear} operations. 275 * It does not support the {@code add} or {@code addAll} operations. 276 * 277 * @return a navigable set view of the keys in this map 278 */ 279 NavigableSet<K> navigableKeySet(); 280 281 /** 282 * Returns a reverse order {@link NavigableSet} view of the keys contained in this map. 283 * The set's iterator returns the keys in descending order. 284 * The set is backed by the map, so changes to the map are reflected in 285 * the set, and vice-versa. If the map is modified while an iteration 286 * over the set is in progress (except through the iterator's own {@code 287 * remove} operation), the results of the iteration are undefined. The 288 * set supports element removal, which removes the corresponding mapping 289 * from the map, via the {@code Iterator.remove}, {@code Set.remove}, 290 * {@code removeAll}, {@code retainAll}, and {@code clear} operations. 291 * It does not support the {@code add} or {@code addAll} operations. 292 * 293 * @return a reverse order navigable set view of the keys in this map 294 */ 295 NavigableSet<K> descendingKeySet(); 296 297 /** 298 * Returns a view of the portion of this map whose keys range from 299 * {@code fromKey} to {@code toKey}. If {@code fromKey} and 300 * {@code toKey} are equal, the returned map is empty unless 301 * {@code fromInclusive} and {@code toInclusive} are both true. The 302 * returned map is backed by this map, so changes in the returned map are 303 * reflected in this map, and vice-versa. The returned map supports all 304 * optional map operations that this map supports. 305 * 306 * <p>The returned map will throw an {@code IllegalArgumentException} 307 * on an attempt to insert a key outside of its range, or to construct a 308 * submap either of whose endpoints lie outside its range. 309 * 310 * @param fromKey low endpoint of the keys in the returned map 311 * @param fromInclusive {@code true} if the low endpoint 312 * is to be included in the returned view 313 * @param toKey high endpoint of the keys in the returned map 314 * @param toInclusive {@code true} if the high endpoint 315 * is to be included in the returned view 316 * @return a view of the portion of this map whose keys range from 317 * {@code fromKey} to {@code toKey} 318 * @throws ClassCastException if {@code fromKey} and {@code toKey} 319 * cannot be compared to one another using this map's comparator 320 * (or, if the map has no comparator, using natural ordering). 321 * Implementations may, but are not required to, throw this 322 * exception if {@code fromKey} or {@code toKey} 323 * cannot be compared to keys currently in the map. 324 * @throws NullPointerException if {@code fromKey} or {@code toKey} 325 * is null and this map does not permit null keys 326 * @throws IllegalArgumentException if {@code fromKey} is greater than 327 * {@code toKey}; or if this map itself has a restricted 328 * range, and {@code fromKey} or {@code toKey} lies 329 * outside the bounds of the range 330 */ 331 NavigableMap<K,V> subMap(K fromKey, boolean fromInclusive, 332 K toKey, boolean toInclusive); 333 334 /** 335 * Returns a view of the portion of this map whose keys are less than (or 336 * equal to, if {@code inclusive} is true) {@code toKey}. The returned 337 * map is backed by this map, so changes in the returned map are reflected 338 * in this map, and vice-versa. The returned map supports all optional 339 * map operations that this map supports. 340 * 341 * <p>The returned map will throw an {@code IllegalArgumentException} 342 * on an attempt to insert a key outside its range. 343 * 344 * @param toKey high endpoint of the keys in the returned map 345 * @param inclusive {@code true} if the high endpoint 346 * is to be included in the returned view 347 * @return a view of the portion of this map whose keys are less than 348 * (or equal to, if {@code inclusive} is true) {@code toKey} 349 * @throws ClassCastException if {@code toKey} is not compatible 350 * with this map's comparator (or, if the map has no comparator, 351 * if {@code toKey} does not implement {@link Comparable}). 352 * Implementations may, but are not required to, throw this 353 * exception if {@code toKey} cannot be compared to keys 354 * currently in the map. 355 * @throws NullPointerException if {@code toKey} is null 356 * and this map does not permit null keys 357 * @throws IllegalArgumentException if this map itself has a 358 * restricted range, and {@code toKey} lies outside the 359 * bounds of the range 360 */ 361 NavigableMap<K,V> headMap(K toKey, boolean inclusive); 362 363 /** 364 * Returns a view of the portion of this map whose keys are greater than (or 365 * equal to, if {@code inclusive} is true) {@code fromKey}. The returned 366 * map is backed by this map, so changes in the returned map are reflected 367 * in this map, and vice-versa. The returned map supports all optional 368 * map operations that this map supports. 369 * 370 * <p>The returned map will throw an {@code IllegalArgumentException} 371 * on an attempt to insert a key outside its range. 372 * 373 * @param fromKey low endpoint of the keys in the returned map 374 * @param inclusive {@code true} if the low endpoint 375 * is to be included in the returned view 376 * @return a view of the portion of this map whose keys are greater than 377 * (or equal to, if {@code inclusive} is true) {@code fromKey} 378 * @throws ClassCastException if {@code fromKey} is not compatible 379 * with this map's comparator (or, if the map has no comparator, 380 * if {@code fromKey} does not implement {@link Comparable}). 381 * Implementations may, but are not required to, throw this 382 * exception if {@code fromKey} cannot be compared to keys 383 * currently in the map. 384 * @throws NullPointerException if {@code fromKey} is null 385 * and this map does not permit null keys 386 * @throws IllegalArgumentException if this map itself has a 387 * restricted range, and {@code fromKey} lies outside the 388 * bounds of the range 389 */ 390 NavigableMap<K,V> tailMap(K fromKey, boolean inclusive); 391 392 /** 393 * {@inheritDoc} 394 * 395 * <p>Equivalent to {@code subMap(fromKey, true, toKey, false)}. 396 * 397 * @throws ClassCastException {@inheritDoc} 398 * @throws NullPointerException {@inheritDoc} 399 * @throws IllegalArgumentException {@inheritDoc} 400 */ 401 SortedMap<K,V> subMap(K fromKey, K toKey); 402 403 /** 404 * {@inheritDoc} 405 * 406 * <p>Equivalent to {@code headMap(toKey, false)}. 407 * 408 * @throws ClassCastException {@inheritDoc} 409 * @throws NullPointerException {@inheritDoc} 410 * @throws IllegalArgumentException {@inheritDoc} 411 */ 412 SortedMap<K,V> headMap(K toKey); 413 414 /** 415 * {@inheritDoc} 416 * 417 * <p>Equivalent to {@code tailMap(fromKey, true)}. 418 * 419 * @throws ClassCastException {@inheritDoc} 420 * @throws NullPointerException {@inheritDoc} 421 * @throws IllegalArgumentException {@inheritDoc} 422 */ 423 SortedMap<K,V> tailMap(K fromKey); 424} 425