Java tutorial
/* * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ /* * This file is available under and governed by the GNU General Public * License version 2 only, as published by the Free Software Foundation. * However, the following notice accompanied the original version of this * file: * * Written by Doug Lea and Josh Bloch with assistance from members of JCP * JSR-166 Expert Group and released to the public domain, as explained at * http://creativecommons.org/publicdomain/zero/1.0/ */ package java.util; /** * A {@link SortedMap} extended with navigation methods returning the * closest matches for given search targets. Methods * {@link #lowerEntry}, {@link #floorEntry}, {@link #ceilingEntry}, * and {@link #higherEntry} return {@code Map.Entry} objects * associated with keys respectively less than, less than or equal, * greater than or equal, and greater than a given key, returning * {@code null} if there is no such key. Similarly, methods * {@link #lowerKey}, {@link #floorKey}, {@link #ceilingKey}, and * {@link #higherKey} return only the associated keys. All of these * methods are designed for locating, not traversing entries. * * <p>A {@code NavigableMap} may be accessed and traversed in either * ascending or descending key order. The {@link #descendingMap} * method returns a view of the map with the senses of all relational * and directional methods inverted. The performance of ascending * operations and views is likely to be faster than that of descending * ones. Methods * {@link #subMap(Object, boolean, Object, boolean) subMap(K, boolean, K, boolean)}, * {@link #headMap(Object, boolean) headMap(K, boolean)}, and * {@link #tailMap(Object, boolean) tailMap(K, boolean)} * differ from the like-named {@code SortedMap} methods in accepting * additional arguments describing whether lower and upper bounds are * inclusive versus exclusive. Submaps of any {@code NavigableMap} * must implement the {@code NavigableMap} interface. * * <p>This interface additionally defines methods {@link #firstEntry}, * {@link #pollFirstEntry}, {@link #lastEntry}, and * {@link #pollLastEntry} that return and/or remove the least and * greatest mappings, if any exist, else returning {@code null}. * * <p>Implementations of entry-returning methods are expected to * return {@code Map.Entry} pairs representing snapshots of mappings * at the time they were produced, and thus generally do <em>not</em> * support the optional {@code Entry.setValue} method. Note however * that it is possible to change mappings in the associated map using * method {@code put}. * * <p>Methods * {@link #subMap(Object, Object) subMap(K, K)}, * {@link #headMap(Object) headMap(K)}, and * {@link #tailMap(Object) tailMap(K)} * are specified to return {@code SortedMap} to allow existing * implementations of {@code SortedMap} to be compatibly retrofitted to * implement {@code NavigableMap}, but extensions and implementations * of this interface are encouraged to override these methods to return * {@code NavigableMap}. Similarly, * {@link #keySet()} can be overridden to return {@link NavigableSet}. * * <p>This interface is a member of the * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework"> * Java Collections Framework</a>. * * @author Doug Lea * @author Josh Bloch * @param <K> the type of keys maintained by this map * @param <V> the type of mapped values * @since 1.6 */ public interface NavigableMap<K, V> extends SortedMap<K, V> { /** * Returns a key-value mapping associated with the greatest key * strictly less than the given key, or {@code null} if there is * no such key. * * @param key the key * @return an entry with the greatest key less than {@code key}, * or {@code null} if there is no such key * @throws ClassCastException if the specified key cannot be compared * with the keys currently in the map * @throws NullPointerException if the specified key is null * and this map does not permit null keys */ Map.Entry<K, V> lowerEntry(K key); /** * Returns the greatest key strictly less than the given key, or * {@code null} if there is no such key. * * @param key the key * @return the greatest key less than {@code key}, * or {@code null} if there is no such key * @throws ClassCastException if the specified key cannot be compared * with the keys currently in the map * @throws NullPointerException if the specified key is null * and this map does not permit null keys */ K lowerKey(K key); /** * Returns a key-value mapping associated with the greatest key * less than or equal to the given key, or {@code null} if there * is no such key. * * @param key the key * @return an entry with the greatest key less than or equal to * {@code key}, or {@code null} if there is no such key * @throws ClassCastException if the specified key cannot be compared * with the keys currently in the map * @throws NullPointerException if the specified key is null * and this map does not permit null keys */ Map.Entry<K, V> floorEntry(K key); /** * Returns the greatest key less than or equal to the given key, * or {@code null} if there is no such key. * * @param key the key * @return the greatest key less than or equal to {@code key}, * or {@code null} if there is no such key * @throws ClassCastException if the specified key cannot be compared * with the keys currently in the map * @throws NullPointerException if the specified key is null * and this map does not permit null keys */ K floorKey(K key); /** * Returns a key-value mapping associated with the least key * greater than or equal to the given key, or {@code null} if * there is no such key. * * @param key the key * @return an entry with the least key greater than or equal to * {@code key}, or {@code null} if there is no such key * @throws ClassCastException if the specified key cannot be compared * with the keys currently in the map * @throws NullPointerException if the specified key is null * and this map does not permit null keys */ Map.Entry<K, V> ceilingEntry(K key); /** * Returns the least key greater than or equal to the given key, * or {@code null} if there is no such key. * * @param key the key * @return the least key greater than or equal to {@code key}, * or {@code null} if there is no such key * @throws ClassCastException if the specified key cannot be compared * with the keys currently in the map * @throws NullPointerException if the specified key is null * and this map does not permit null keys */ K ceilingKey(K key); /** * Returns a key-value mapping associated with the least key * strictly greater than the given key, or {@code null} if there * is no such key. * * @param key the key * @return an entry with the least key greater than {@code key}, * or {@code null} if there is no such key * @throws ClassCastException if the specified key cannot be compared * with the keys currently in the map * @throws NullPointerException if the specified key is null * and this map does not permit null keys */ Map.Entry<K, V> higherEntry(K key); /** * Returns the least key strictly greater than the given key, or * {@code null} if there is no such key. * * @param key the key * @return the least key greater than {@code key}, * or {@code null} if there is no such key * @throws ClassCastException if the specified key cannot be compared * with the keys currently in the map * @throws NullPointerException if the specified key is null * and this map does not permit null keys */ K higherKey(K key); /** * Returns a key-value mapping associated with the least * key in this map, or {@code null} if the map is empty. * * @return an entry with the least key, * or {@code null} if this map is empty */ Map.Entry<K, V> firstEntry(); /** * Returns a key-value mapping associated with the greatest * key in this map, or {@code null} if the map is empty. * * @return an entry with the greatest key, * or {@code null} if this map is empty */ Map.Entry<K, V> lastEntry(); /** * Removes and returns a key-value mapping associated with * the least key in this map, or {@code null} if the map is empty. * * @return the removed first entry of this map, * or {@code null} if this map is empty */ Map.Entry<K, V> pollFirstEntry(); /** * Removes and returns a key-value mapping associated with * the greatest key in this map, or {@code null} if the map is empty. * * @return the removed last entry of this map, * or {@code null} if this map is empty */ Map.Entry<K, V> pollLastEntry(); /** * Returns a reverse order view of the mappings contained in this map. * The descending map is backed by this map, so changes to the map are * reflected in the descending map, and vice-versa. If either map is * modified while an iteration over a collection view of either map * is in progress (except through the iterator's own {@code remove} * operation), the results of the iteration are undefined. * * <p>The returned map has an ordering equivalent to * {@link Collections#reverseOrder(Comparator) Collections.reverseOrder}{@code (comparator())}. * The expression {@code m.descendingMap().descendingMap()} returns a * view of {@code m} essentially equivalent to {@code m}. * * @return a reverse order view of this map */ NavigableMap<K, V> descendingMap(); /** * Returns a {@link NavigableSet} view of the keys contained in this map. * The set's iterator returns the keys in ascending order. * The set is backed by the map, so changes to the map are reflected in * the set, and vice-versa. If the map is modified while an iteration * over the set is in progress (except through the iterator's own {@code * remove} operation), the results of the iteration are undefined. The * set supports element removal, which removes the corresponding mapping * from the map, via the {@code Iterator.remove}, {@code Set.remove}, * {@code removeAll}, {@code retainAll}, and {@code clear} operations. * It does not support the {@code add} or {@code addAll} operations. * * @return a navigable set view of the keys in this map */ NavigableSet<K> navigableKeySet(); /** * Returns a reverse order {@link NavigableSet} view of the keys contained in this map. * The set's iterator returns the keys in descending order. * The set is backed by the map, so changes to the map are reflected in * the set, and vice-versa. If the map is modified while an iteration * over the set is in progress (except through the iterator's own {@code * remove} operation), the results of the iteration are undefined. The * set supports element removal, which removes the corresponding mapping * from the map, via the {@code Iterator.remove}, {@code Set.remove}, * {@code removeAll}, {@code retainAll}, and {@code clear} operations. * It does not support the {@code add} or {@code addAll} operations. * * @return a reverse order navigable set view of the keys in this map */ NavigableSet<K> descendingKeySet(); /** * Returns a view of the portion of this map whose keys range from * {@code fromKey} to {@code toKey}. If {@code fromKey} and * {@code toKey} are equal, the returned map is empty unless * {@code fromInclusive} and {@code toInclusive} are both true. The * returned map is backed by this map, so changes in the returned map are * reflected in this map, and vice-versa. The returned map supports all * optional map operations that this map supports. * * <p>The returned map will throw an {@code IllegalArgumentException} * on an attempt to insert a key outside of its range, or to construct a * submap either of whose endpoints lie outside its range. * * @param fromKey low endpoint of the keys in the returned map * @param fromInclusive {@code true} if the low endpoint * is to be included in the returned view * @param toKey high endpoint of the keys in the returned map * @param toInclusive {@code true} if the high endpoint * is to be included in the returned view * @return a view of the portion of this map whose keys range from * {@code fromKey} to {@code toKey} * @throws ClassCastException if {@code fromKey} and {@code toKey} * cannot be compared to one another using this map's comparator * (or, if the map has no comparator, using natural ordering). * Implementations may, but are not required to, throw this * exception if {@code fromKey} or {@code toKey} * cannot be compared to keys currently in the map. * @throws NullPointerException if {@code fromKey} or {@code toKey} * is null and this map does not permit null keys * @throws IllegalArgumentException if {@code fromKey} is greater than * {@code toKey}; or if this map itself has a restricted * range, and {@code fromKey} or {@code toKey} lies * outside the bounds of the range */ NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive); /** * Returns a view of the portion of this map whose keys are less than (or * equal to, if {@code inclusive} is true) {@code toKey}. The returned * map is backed by this map, so changes in the returned map are reflected * in this map, and vice-versa. The returned map supports all optional * map operations that this map supports. * * <p>The returned map will throw an {@code IllegalArgumentException} * on an attempt to insert a key outside its range. * * @param toKey high endpoint of the keys in the returned map * @param inclusive {@code true} if the high endpoint * is to be included in the returned view * @return a view of the portion of this map whose keys are less than * (or equal to, if {@code inclusive} is true) {@code toKey} * @throws ClassCastException if {@code toKey} is not compatible * with this map's comparator (or, if the map has no comparator, * if {@code toKey} does not implement {@link Comparable}). * Implementations may, but are not required to, throw this * exception if {@code toKey} cannot be compared to keys * currently in the map. * @throws NullPointerException if {@code toKey} is null * and this map does not permit null keys * @throws IllegalArgumentException if this map itself has a * restricted range, and {@code toKey} lies outside the * bounds of the range */ NavigableMap<K, V> headMap(K toKey, boolean inclusive); /** * Returns a view of the portion of this map whose keys are greater than (or * equal to, if {@code inclusive} is true) {@code fromKey}. The returned * map is backed by this map, so changes in the returned map are reflected * in this map, and vice-versa. The returned map supports all optional * map operations that this map supports. * * <p>The returned map will throw an {@code IllegalArgumentException} * on an attempt to insert a key outside its range. * * @param fromKey low endpoint of the keys in the returned map * @param inclusive {@code true} if the low endpoint * is to be included in the returned view * @return a view of the portion of this map whose keys are greater than * (or equal to, if {@code inclusive} is true) {@code fromKey} * @throws ClassCastException if {@code fromKey} is not compatible * with this map's comparator (or, if the map has no comparator, * if {@code fromKey} does not implement {@link Comparable}). * Implementations may, but are not required to, throw this * exception if {@code fromKey} cannot be compared to keys * currently in the map. * @throws NullPointerException if {@code fromKey} is null * and this map does not permit null keys * @throws IllegalArgumentException if this map itself has a * restricted range, and {@code fromKey} lies outside the * bounds of the range */ NavigableMap<K, V> tailMap(K fromKey, boolean inclusive); /** * {@inheritDoc} * * <p>Equivalent to {@code subMap(fromKey, true, toKey, false)}. * * @throws ClassCastException {@inheritDoc} * @throws NullPointerException {@inheritDoc} * @throws IllegalArgumentException {@inheritDoc} */ SortedMap<K, V> subMap(K fromKey, K toKey); /** * {@inheritDoc} * * <p>Equivalent to {@code headMap(toKey, false)}. * * @throws ClassCastException {@inheritDoc} * @throws NullPointerException {@inheritDoc} * @throws IllegalArgumentException {@inheritDoc} */ SortedMap<K, V> headMap(K toKey); /** * {@inheritDoc} * * <p>Equivalent to {@code tailMap(fromKey, true)}. * * @throws ClassCastException {@inheritDoc} * @throws NullPointerException {@inheritDoc} * @throws IllegalArgumentException {@inheritDoc} */ SortedMap<K, V> tailMap(K fromKey); }