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 7 package 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 overridden 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 */ 66 public 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 Map.Entry<K,V> firstEntry(); 188 189 /** 190 * Returns a key-value mapping associated with the greatest 191 * key in this map, or {@code null} if the map is empty. 192 */ 193 Map.Entry<K,V> lastEntry(); 194 195 /** 196 * Removes and returns a key-value mapping associated with 197 * the least key in this map, or {@code null} if the map is empty. 198 * 199 * @return the removed first entry of this map, 200 * or {@code null} if this map is empty 201 */ 202 Map.Entry<K,V> pollFirstEntry(); 203 204 /** 205 * Removes and returns a key-value mapping associated with 206 * the greatest key in this map, or {@code null} if the map is empty. 207 * 208 * @return the removed last entry of this map, 209 * or {@code null} if this map is empty 210 */ 211 Map.Entry<K,V> pollLastEntry(); 212 213 /** 214 * Returns a reverse order view of the mappings contained in this map. 215 * The descending map is backed by this map, so changes to the map are 216 * reflected in the descending map, and vice-versa. If either map is 217 * modified while an iteration over a collection view of either map 218 * is in progress (except through the iterator's own {@code remove} 219 * operation), the results of the iteration are undefined. 220 * 221 * <p>The returned map has an ordering equivalent to 222 * <tt>{@link Collections#reverseOrder(Comparator) Collections.reverseOrder}(comparator())</tt>. 223 * The expression {@code m.descendingMap().descendingMap()} returns a 224 * view of {@code m} essentially equivalent to {@code m}. 225 * 226 * @return a reverse order view of this map 227 */ 228 NavigableMap<K,V> descendingMap(); 229 230 /** 231 * Returns a {@link NavigableSet} view of the keys contained in this map. 232 * The set's iterator returns the keys in ascending order. 233 * The set is backed by the map, so changes to the map are reflected in 234 * the set, and vice-versa. If the map is modified while an iteration 235 * over the set is in progress (except through the iterator's own {@code 236 * remove} operation), the results of the iteration are undefined. The 237 * set supports element removal, which removes the corresponding mapping 238 * from the map, via the {@code Iterator.remove}, {@code Set.remove}, 239 * {@code removeAll}, {@code retainAll}, and {@code clear} operations. 240 * It does not support the {@code add} or {@code addAll} operations. 241 * 242 * @return a navigable set view of the keys in this map 243 */ 244 NavigableSet<K> navigableKeySet(); 245 246 /** 247 * Returns a reverse order {@link NavigableSet} view of the keys contained in this map. 248 * The set's iterator returns the keys in descending order. 249 * The set is backed by the map, so changes to the map are reflected in 250 * the set, and vice-versa. If the map is modified while an iteration 251 * over the set is in progress (except through the iterator's own {@code 252 * remove} operation), the results of the iteration are undefined. The 253 * set supports element removal, which removes the corresponding mapping 254 * from the map, via the {@code Iterator.remove}, {@code Set.remove}, 255 * {@code removeAll}, {@code retainAll}, and {@code clear} operations. 256 * It does not support the {@code add} or {@code addAll} operations. 257 * 258 * @return a reverse order navigable set view of the keys in this map 259 */ 260 NavigableSet<K> descendingKeySet(); 261 262 /** 263 * Returns a view of the portion of this map whose keys range from 264 * {@code fromKey} to {@code toKey}. If {@code fromKey} and 265 * {@code toKey} are equal, the returned map is empty unless 266 * {@code fromExclusive} and {@code toExclusive} are both true. The 267 * returned map is backed by this map, so changes in the returned map are 268 * reflected in this map, and vice-versa. The returned map supports all 269 * optional map operations that this map supports. 270 * 271 * <p>The returned map will throw an {@code IllegalArgumentException} 272 * on an attempt to insert a key outside of its range, or to construct a 273 * submap either of whose endpoints lie outside its range. 274 * 275 * @param fromKey low endpoint of the keys in the returned map 276 * @param fromInclusive {@code true} if the low endpoint 277 * is to be included in the returned view 278 * @param toKey high endpoint of the keys in the returned map 279 * @param toInclusive {@code true} if the high endpoint 280 * is to be included in the returned view 281 * @return a view of the portion of this map whose keys range from 282 * {@code fromKey} to {@code toKey} 283 * @throws ClassCastException if {@code fromKey} and {@code toKey} 284 * cannot be compared to one another using this map's comparator 285 * (or, if the map has no comparator, using natural ordering). 286 * Implementations may, but are not required to, throw this 287 * exception if {@code fromKey} or {@code toKey} 288 * cannot be compared to keys currently in the map. 289 * @throws NullPointerException if {@code fromKey} or {@code toKey} 290 * is null and this map does not permit null keys 291 * @throws IllegalArgumentException if {@code fromKey} is greater than 292 * {@code toKey}; or if this map itself has a restricted 293 * range, and {@code fromKey} or {@code toKey} lies 294 * outside the bounds of the range 295 */ 296 NavigableMap<K,V> subMap(K fromKey, boolean fromInclusive, 297 K toKey, boolean toInclusive); 298 299 /** 300 * Returns a view of the portion of this map whose keys are less than (or 301 * equal to, if {@code inclusive} is true) {@code toKey}. The returned 302 * map is backed by this map, so changes in the returned map are reflected 303 * in this map, and vice-versa. The returned map supports all optional 304 * 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 its range. 308 * 309 * @param toKey high endpoint of the keys in the returned map 310 * @param inclusive {@code true} if the high endpoint 311 * is to be included in the returned view 312 * @return a view of the portion of this map whose keys are less than 313 * (or equal to, if {@code inclusive} is true) {@code toKey} 314 * @throws ClassCastException if {@code toKey} is not compatible 315 * with this map's comparator (or, if the map has no comparator, 316 * if {@code toKey} does not implement {@link Comparable}). 317 * Implementations may, but are not required to, throw this 318 * exception if {@code toKey} cannot be compared to keys 319 * currently in the map. 320 * @throws NullPointerException if {@code toKey} is null 321 * and this map does not permit null keys 322 * @throws IllegalArgumentException if this map itself has a 323 * restricted range, and {@code toKey} lies outside the 324 * bounds of the range 325 */ 326 NavigableMap<K,V> headMap(K toKey, boolean inclusive); 327 328 /** 329 * Returns a view of the portion of this map whose keys are greater than (or 330 * equal to, if {@code inclusive} is true) {@code fromKey}. The returned 331 * map is backed by this map, so changes in the returned map are reflected 332 * in this map, and vice-versa. The returned map supports all optional 333 * map operations that this map supports. 334 * 335 * <p>The returned map will throw an {@code IllegalArgumentException} 336 * on an attempt to insert a key outside its range. 337 * 338 * @param fromKey low endpoint of the keys in the returned map 339 * @param inclusive {@code true} if the low endpoint 340 * is to be included in the returned view 341 * @return a view of the portion of this map whose keys are greater than 342 * (or equal to, if {@code inclusive} is true) {@code fromKey} 343 * @throws ClassCastException if {@code fromKey} is not compatible 344 * with this map's comparator (or, if the map has no comparator, 345 * if {@code fromKey} does not implement {@link Comparable}). 346 * Implementations may, but are not required to, throw this 347 * exception if {@code fromKey} cannot be compared to keys 348 * currently in the map. 349 * @throws NullPointerException if {@code fromKey} is null 350 * and this map does not permit null keys 351 * @throws IllegalArgumentException if this map itself has a 352 * restricted range, and {@code fromKey} lies outside the 353 * bounds of the range 354 */ 355 NavigableMap<K,V> tailMap(K fromKey, boolean inclusive); 356 357 /** 358 * {@inheritDoc} 359 * 360 * <p>Equivalent to {@code subMap(fromKey, true, toKey, false)}. 361 * 362 * @throws ClassCastException {@inheritDoc} 363 * @throws NullPointerException {@inheritDoc} 364 * @throws IllegalArgumentException {@inheritDoc} 365 */ 366 SortedMap<K,V> subMap(K fromKey, K toKey); 367 368 /** 369 * {@inheritDoc} 370 * 371 * <p>Equivalent to {@code headMap(toKey, false)}. 372 * 373 * @throws ClassCastException {@inheritDoc} 374 * @throws NullPointerException {@inheritDoc} 375 * @throws IllegalArgumentException {@inheritDoc} 376 */ 377 SortedMap<K,V> headMap(K toKey); 378 379 /** 380 * {@inheritDoc} 381 * 382 * <p>Equivalent to {@code tailMap(fromKey, true)}. 383 * 384 * @throws ClassCastException {@inheritDoc} 385 * @throws NullPointerException {@inheritDoc} 386 * @throws IllegalArgumentException {@inheritDoc} 387 */ 388 SortedMap<K,V> tailMap(K fromKey); 389 } 390
