/* * Copyright (c) 1998, 2006, Oracle and/or its affiliates. All rights reserved. * 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. */ package java.util; /** * A {@link Map} that further provides a <em>total ordering</em> on its keys. * The map is ordered according to the {@linkplain Comparable natural * ordering} of its keys, or by a {@link Comparator} typically * provided at sorted map creation time.  This order is reflected when * iterating over the sorted map's collection views (returned by the * {@code entrySet}, {@code keySet} and {@code values} methods). * Several additional operations are provided to take advantage of the * ordering.  (This interface is the map analogue of {@link SortedSet}.) * * <p>All keys inserted into a sorted map must implement the {@code Comparable} * interface (or be accepted by the specified comparator).  Furthermore, all * such keys must be <em>mutually comparable</em>: {@code k1.compareTo(k2)} (or * {@code comparator.compare(k1, k2)}) must not throw a * {@code ClassCastException} for any keys {@code k1} and {@code k2} in * the sorted map.  Attempts to violate this restriction will cause the * offending method or constructor invocation to throw a * {@code ClassCastException}. * * <p>Note that the ordering maintained by a sorted map (whether or not an * explicit comparator is provided) must be <em>consistent with equals</em> if * the sorted map is to correctly implement the {@code Map} interface.  (See * the {@code Comparable} interface or {@code Comparator} interface for a * precise definition of <em>consistent with equals</em>.)  This is so because * the {@code Map} interface is defined in terms of the {@code equals} * operation, but a sorted map performs all key comparisons using its * {@code compareTo} (or {@code compare}) method, so two keys that are * deemed equal by this method are, from the standpoint of the sorted map, * equal.  The behavior of a tree map <em>is</em> well-defined even if its * ordering is inconsistent with equals; it just fails to obey the general * contract of the {@code Map} interface. * * <p>All general-purpose sorted map implementation classes should provide four * "standard" constructors. It is not possible to enforce this recommendation * though as required constructors cannot be specified by interfaces. The * expected "standard" constructors for all sorted map implementations are: * <ol> *   <li>A void (no arguments) constructor, which creates an empty sorted map *   sorted according to the natural ordering of its keys.</li> *   <li>A constructor with a single argument of type {@code Comparator}, which *   creates an empty sorted map sorted according to the specified comparator.</li> *   <li>A constructor with a single argument of type {@code Map}, which creates *   a new map with the same key-value mappings as its argument, sorted *   according to the keys' natural ordering.</li> *   <li>A constructor with a single argument of type {@code SortedMap}, which *   creates a new sorted map with the same key-value mappings and the same *   ordering as the input sorted map.</li> * </ol> * * <p><strong>Note</strong>: several methods return submaps with restricted key * ranges. Such ranges are <em>half-open</em>, that is, they include their low * endpoint but not their high endpoint (where applicable).  If you need a * <em>closed range</em> (which includes both endpoints), and the key type * allows for calculation of the successor of a given key, merely request * the subrange from {@code lowEndpoint} to * {@code successor(highEndpoint)}.  For example, suppose that {@code m} * is a map whose keys are strings.  The following idiom obtains a view * containing all of the key-value mappings in {@code m} whose keys are * between {@code low} and {@code high}, inclusive:<pre> *   SortedMap&lt;String, V&gt; sub = m.subMap(low, high+"\0");</pre> * * A similar technique can be used to generate an <em>open range</em> * (which contains neither endpoint).  The following idiom obtains a * view containing all of the key-value mappings in {@code m} whose keys * are between {@code low} and {@code high}, exclusive:<pre> *   SortedMap&lt;String, V&gt; sub = m.subMap(low+"\0", high);</pre> * * <p>This interface is a member of the * <a href="{@docRoot}/../technotes/guides/collections/index.html"> * Java Collections Framework</a>. * * @param <K> the type of keys maintained by this map * @param <V> the type of mapped values * * @author  Josh Bloch * @see Map * @see TreeMap * @see SortedSet * @see Comparator * @see Comparable * @see Collection * @see ClassCastException * @since 1.2 */ public interface SortedMap<K,V> extends Map<K,V> {    /**     * Returns the comparator used to order the keys in this map, or     * {@code null} if this map uses the {@linkplain Comparable     * natural ordering} of its keys.     *     * @return the comparator used to order the keys in this map,     *         or {@code null} if this map uses the natural ordering     *         of its keys     */    Comparator<? super K> comparator();     /**     * Returns a view of the portion of this map whose keys range from     * {@code fromKey}, inclusive, to {@code toKey}, exclusive.  (If     * {@code fromKey} and {@code toKey} are equal, the returned map     * is empty.)  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 (inclusive) of the keys in the returned map     * @param toKey high endpoint (exclusive) of the keys in the returned map     * @return a view of the portion of this map whose keys range from     *         {@code fromKey}, inclusive, to {@code toKey}, exclusive     * @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     */    SortedMap<K,V> subMap(K fromKey, K toKey);     /**     * Returns a view of the portion of this map whose keys are     * strictly less than {@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 (exclusive) of the keys in the returned map     * @return a view of the portion of this map whose keys are strictly     *         less than {@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     */    SortedMap<K,V> headMap(K toKey);     /**     * Returns a view of the portion of this map whose keys are     * greater than or equal to {@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 (inclusive) of the keys in the returned map     * @return a view of the portion of this map whose keys are greater     *         than or equal to {@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     */    SortedMap<K,V> tailMap(K fromKey);     /**     * Returns the first (lowest) key currently in this map.     *     * @return the first (lowest) key currently in this map     * @throws NoSuchElementException if this map is empty     */    K firstKey();     /**     * Returns the last (highest) key currently in this map.     *     * @return the last (highest) key currently in this map     * @throws NoSuchElementException if this map is empty     */    K lastKey();     /**     * Returns a {@link Set} 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 set view of the keys contained in this map, sorted in     *         ascending order     */    Set<K> keySet();     /**     * Returns a {@link Collection} view of the values contained in this map.     * The collection's iterator returns the values in ascending order     * of the corresponding keys.     * The collection is backed by the map, so changes to the map are     * reflected in the collection, and vice-versa.  If the map is     * modified while an iteration over the collection is in progress     * (except through the iterator's own {@code remove} operation),     * the results of the iteration are undefined.  The collection     * supports element removal, which removes the corresponding     * mapping from the map, via the {@code Iterator.remove},     * {@code Collection.remove}, {@code removeAll},     * {@code retainAll} and {@code clear} operations.  It does not     * support the {@code add} or {@code addAll} operations.     *     * @return a collection view of the values contained in this map,     *         sorted in ascending key order     */    Collection<V> values();     /**     * Returns a {@link Set} view of the mappings contained in this map.     * The set's iterator returns the entries in ascending key 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, or through the     * {@code setValue} operation on a map entry returned by the     * iterator) 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 set view of the mappings contained in this map,     *         sorted in ascending key order     */    Set<Map.Entry<K, V>> entrySet();}