1/* 2 * Written by Doug Lea and Josh Bloch with assistance from members of JCP 3 * JSR-166 Expert Group and released to the public domain, as explained at 4 * http://creativecommons.org/publicdomain/zero/1.0/ 5 */ 6 7package java.util; 8 9// BEGIN android-note 10// removed link to collections framework docs 11// END android-note 12 13/** 14 * A {@link SortedMap} extended with navigation methods returning the 15 * closest matches for given search targets. Methods 16 * {@code lowerEntry}, {@code floorEntry}, {@code ceilingEntry}, 17 * and {@code higherEntry} return {@code Map.Entry} objects 18 * associated with keys respectively less than, less than or equal, 19 * greater than or equal, and greater than a given key, returning 20 * {@code null} if there is no such key. Similarly, methods 21 * {@code lowerKey}, {@code floorKey}, {@code ceilingKey}, and 22 * {@code higherKey} return only the associated keys. All of these 23 * methods are designed for locating, not traversing entries. 24 * 25 * <p>A {@code NavigableMap} may be accessed and traversed in either 26 * ascending or descending key order. The {@code descendingMap} 27 * method returns a view of the map with the senses of all relational 28 * and directional methods inverted. The performance of ascending 29 * operations and views is likely to be faster than that of descending 30 * ones. Methods {@code subMap}, {@code headMap}, 31 * and {@code tailMap} differ from the like-named {@code 32 * SortedMap} methods in accepting additional arguments describing 33 * whether lower and upper bounds are inclusive versus exclusive. 34 * Submaps of any {@code NavigableMap} must implement the {@code 35 * NavigableMap} interface. 36 * 37 * <p>This interface additionally defines methods {@code firstEntry}, 38 * {@code pollFirstEntry}, {@code lastEntry}, and 39 * {@code pollLastEntry} that return and/or remove the least and 40 * greatest mappings, if any exist, else returning {@code null}. 41 * 42 * <p>Implementations of entry-returning methods are expected to 43 * return {@code Map.Entry} pairs representing snapshots of mappings 44 * at the time they were produced, and thus generally do <em>not</em> 45 * support the optional {@code Entry.setValue} method. Note however 46 * that it is possible to change mappings in the associated map using 47 * method {@code put}. 48 * 49 * <p>Methods 50 * {@link #subMap(Object, Object) subMap(K, K)}, 51 * {@link #headMap(Object) headMap(K)}, and 52 * {@link #tailMap(Object) tailMap(K)} 53 * are specified to return {@code SortedMap} to allow existing 54 * implementations of {@code SortedMap} to be compatibly retrofitted to 55 * implement {@code NavigableMap}, but extensions and implementations 56 * of this interface are encouraged to override these methods to return 57 * {@code NavigableMap}. Similarly, 58 * {@link #keySet()} can be overriden to return {@code NavigableSet}. 59 * 60 * @author Doug Lea 61 * @author Josh Bloch 62 * @param <K> the type of keys maintained by this map 63 * @param <V> the type of mapped values 64 * @since 1.6 65 */ 66public interface NavigableMap<K,V> extends SortedMap<K,V> { 67 /** 68 * Returns a key-value mapping associated with the greatest key 69 * strictly less than the given key, or {@code null} if there is 70 * no such key. 71 * 72 * @param key the key 73 * @return an entry with the greatest key less than {@code key}, 74 * or {@code null} if there is no such key 75 * @throws ClassCastException if the specified key cannot be compared 76 * with the keys currently in the map 77 * @throws NullPointerException if the specified key is null 78 * and this map does not permit null keys 79 */ 80 Map.Entry<K,V> lowerEntry(K key); 81 82 /** 83 * Returns the greatest key strictly less than the given key, or 84 * {@code null} if there is no such key. 85 * 86 * @param key the key 87 * @return the greatest key less than {@code key}, 88 * or {@code null} if there is no such key 89 * @throws ClassCastException if the specified key cannot be compared 90 * with the keys currently in the map 91 * @throws NullPointerException if the specified key is null 92 * and this map does not permit null keys 93 */ 94 K lowerKey(K key); 95 96 /** 97 * Returns a key-value mapping associated with the greatest key 98 * less than or equal to the given key, or {@code null} if there 99 * is no such key. 100 * 101 * @param key the key 102 * @return an entry with the greatest key less than or equal to 103 * {@code key}, 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> floorEntry(K key); 110 111 /** 112 * Returns the greatest key less than or equal to the given key, 113 * or {@code null} if there is no such key. 114 * 115 * @param key the key 116 * @return the greatest key less than or equal to {@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 floorKey(K key); 124 125 /** 126 * Returns a key-value mapping associated with the least key 127 * greater than or equal to the given key, or {@code null} if 128 * there is no such key. 129 * 130 * @param key the key 131 * @return an entry with the least key greater 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> ceilingEntry(K key); 139 140 /** 141 * Returns the least key greater 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 least key greater 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 ceilingKey(K key); 153 154 /** 155 * Returns a key-value mapping associated with the least key 156 * strictly greater than the given key, or {@code null} if there 157 * is no such key. 158 * 159 * @param key the key 160 * @return an entry with the least key greater than {@code key}, 161 * 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> higherEntry(K key); 168 169 /** 170 * Returns the least key strictly greater than the given key, or 171 * {@code null} if there is no such key. 172 * 173 * @param key the key 174 * @return the least key greater than {@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 higherKey(K key); 182 183 /** 184 * Returns a key-value mapping associated with the least 185 * key in this map, or {@code null} if the map is empty. 186 * 187 * @return an entry with the least key, 188 * or {@code null} if this map is empty 189 */ 190 Map.Entry<K,V> firstEntry(); 191 192 /** 193 * Returns a key-value mapping associated with the greatest 194 * key in this map, or {@code null} if the map is empty. 195 * 196 * @return an entry with the greatest key, 197 * or {@code null} if this map is empty 198 */ 199 Map.Entry<K,V> lastEntry(); 200 201 /** 202 * Removes and returns a key-value mapping associated with 203 * the least key in this map, or {@code null} if the map is empty. 204 * 205 * @return the removed first entry of this map, 206 * or {@code null} if this map is empty 207 */ 208 Map.Entry<K,V> pollFirstEntry(); 209 210 /** 211 * Removes and returns a key-value mapping associated with 212 * the greatest key in this map, or {@code null} if the map is empty. 213 * 214 * @return the removed last entry of this map, 215 * or {@code null} if this map is empty 216 */ 217 Map.Entry<K,V> pollLastEntry(); 218 219 /** 220 * Returns a reverse order view of the mappings contained in this map. 221 * The descending map is backed by this map, so changes to the map are 222 * reflected in the descending map, and vice-versa. If either map is 223 * modified while an iteration over a collection view of either map 224 * is in progress (except through the iterator's own {@code remove} 225 * operation), the results of the iteration are undefined. 226 * 227 * <p>The returned map has an ordering equivalent to 228 * <tt>{@link Collections#reverseOrder(Comparator) Collections.reverseOrder}(comparator())</tt>. 229 * The expression {@code m.descendingMap().descendingMap()} returns a 230 * view of {@code m} essentially equivalent to {@code m}. 231 * 232 * @return a reverse order view of this map 233 */ 234 NavigableMap<K,V> descendingMap(); 235 236 /** 237 * Returns a {@link NavigableSet} view of the keys contained in this map. 238 * The set's iterator returns the keys in ascending order. 239 * The set is backed by the map, so changes to the map are reflected in 240 * the set, and vice-versa. If the map is modified while an iteration 241 * over the set is in progress (except through the iterator's own {@code 242 * remove} operation), the results of the iteration are undefined. The 243 * set supports element removal, which removes the corresponding mapping 244 * from the map, via the {@code Iterator.remove}, {@code Set.remove}, 245 * {@code removeAll}, {@code retainAll}, and {@code clear} operations. 246 * It does not support the {@code add} or {@code addAll} operations. 247 * 248 * @return a navigable set view of the keys in this map 249 */ 250 NavigableSet<K> navigableKeySet(); 251 252 /** 253 * Returns a reverse order {@link NavigableSet} view of the keys contained in this map. 254 * The set's iterator returns the keys in descending order. 255 * The set is backed by the map, so changes to the map are reflected in 256 * the set, and vice-versa. If the map is modified while an iteration 257 * over the set is in progress (except through the iterator's own {@code 258 * remove} operation), the results of the iteration are undefined. The 259 * set supports element removal, which removes the corresponding mapping 260 * from the map, via the {@code Iterator.remove}, {@code Set.remove}, 261 * {@code removeAll}, {@code retainAll}, and {@code clear} operations. 262 * It does not support the {@code add} or {@code addAll} operations. 263 * 264 * @return a reverse order navigable set view of the keys in this map 265 */ 266 NavigableSet<K> descendingKeySet(); 267 268 /** 269 * Returns a view of the portion of this map whose keys range from 270 * {@code fromKey} to {@code toKey}. If {@code fromKey} and 271 * {@code toKey} are equal, the returned map is empty unless 272 * {@code fromExclusive} and {@code toExclusive} are both true. The 273 * returned map is backed by this map, so changes in the returned map are 274 * reflected in this map, and vice-versa. The returned map supports all 275 * optional map operations that this map supports. 276 * 277 * <p>The returned map will throw an {@code IllegalArgumentException} 278 * on an attempt to insert a key outside of its range, or to construct a 279 * submap either of whose endpoints lie outside its range. 280 * 281 * @param fromKey low endpoint of the keys in the returned map 282 * @param fromInclusive {@code true} if the low endpoint 283 * is to be included in the returned view 284 * @param toKey high endpoint of the keys in the returned map 285 * @param toInclusive {@code true} if the high endpoint 286 * is to be included in the returned view 287 * @return a view of the portion of this map whose keys range from 288 * {@code fromKey} to {@code toKey} 289 * @throws ClassCastException if {@code fromKey} and {@code toKey} 290 * cannot be compared to one another using this map's comparator 291 * (or, if the map has no comparator, using natural ordering). 292 * Implementations may, but are not required to, throw this 293 * exception if {@code fromKey} or {@code toKey} 294 * cannot be compared to keys currently in the map. 295 * @throws NullPointerException if {@code fromKey} or {@code toKey} 296 * is null and this map does not permit null keys 297 * @throws IllegalArgumentException if {@code fromKey} is greater than 298 * {@code toKey}; or if this map itself has a restricted 299 * range, and {@code fromKey} or {@code toKey} lies 300 * outside the bounds of the range 301 */ 302 NavigableMap<K,V> subMap(K fromKey, boolean fromInclusive, 303 K toKey, boolean toInclusive); 304 305 /** 306 * Returns a view of the portion of this map whose keys are less than (or 307 * equal to, if {@code inclusive} is true) {@code toKey}. The returned 308 * map is backed by this map, so changes in the returned map are reflected 309 * in this map, and vice-versa. The returned map supports all optional 310 * map operations that this map supports. 311 * 312 * <p>The returned map will throw an {@code IllegalArgumentException} 313 * on an attempt to insert a key outside its range. 314 * 315 * @param toKey high endpoint of the keys in the returned map 316 * @param inclusive {@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 are less than 319 * (or equal to, if {@code inclusive} is true) {@code toKey} 320 * @throws ClassCastException if {@code toKey} is not compatible 321 * with this map's comparator (or, if the map has no comparator, 322 * if {@code toKey} does not implement {@link Comparable}). 323 * Implementations may, but are not required to, throw this 324 * exception if {@code toKey} cannot be compared to keys 325 * currently in the map. 326 * @throws NullPointerException if {@code toKey} is null 327 * and this map does not permit null keys 328 * @throws IllegalArgumentException if this map itself has a 329 * restricted range, and {@code toKey} lies outside the 330 * bounds of the range 331 */ 332 NavigableMap<K,V> headMap(K toKey, boolean inclusive); 333 334 /** 335 * Returns a view of the portion of this map whose keys are greater than (or 336 * equal to, if {@code inclusive} is true) {@code fromKey}. 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 fromKey low endpoint of the keys in the returned map 345 * @param inclusive {@code true} if the low endpoint 346 * is to be included in the returned view 347 * @return a view of the portion of this map whose keys are greater than 348 * (or equal to, if {@code inclusive} is true) {@code fromKey} 349 * @throws ClassCastException if {@code fromKey} is not compatible 350 * with this map's comparator (or, if the map has no comparator, 351 * if {@code fromKey} does not implement {@link Comparable}). 352 * Implementations may, but are not required to, throw this 353 * exception if {@code fromKey} cannot be compared to keys 354 * currently in the map. 355 * @throws NullPointerException if {@code fromKey} 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 fromKey} lies outside the 359 * bounds of the range 360 */ 361 NavigableMap<K,V> tailMap(K fromKey, boolean inclusive); 362 363 /** 364 * {@inheritDoc} 365 * 366 * <p>Equivalent to {@code subMap(fromKey, true, toKey, false)}. 367 * 368 * @throws ClassCastException {@inheritDoc} 369 * @throws NullPointerException {@inheritDoc} 370 * @throws IllegalArgumentException {@inheritDoc} 371 */ 372 SortedMap<K,V> subMap(K fromKey, K toKey); 373 374 /** 375 * {@inheritDoc} 376 * 377 * <p>Equivalent to {@code headMap(toKey, false)}. 378 * 379 * @throws ClassCastException {@inheritDoc} 380 * @throws NullPointerException {@inheritDoc} 381 * @throws IllegalArgumentException {@inheritDoc} 382 */ 383 SortedMap<K,V> headMap(K toKey); 384 385 /** 386 * {@inheritDoc} 387 * 388 * <p>Equivalent to {@code tailMap(fromKey, true)}. 389 * 390 * @throws ClassCastException {@inheritDoc} 391 * @throws NullPointerException {@inheritDoc} 392 * @throws IllegalArgumentException {@inheritDoc} 393 */ 394 SortedMap<K,V> tailMap(K fromKey); 395} 396