/*

 * Copyright 1998-2006 Sun Microsystems, Inc.  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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

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 */

package java.util;

/**

 * A {@link Map} that further provides a <i>total ordering</i> 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

 * <tt>entrySet</tt>, <tt>keySet</tt> and <tt>values</tt> 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 <tt>Comparable</tt>

 * interface (or be accepted by the specified comparator).  Furthermore, all

 * such keys must be <i>mutually comparable</i>: <tt>k1.compareTo(k2)</tt> (or

 * <tt>comparator.compare(k1, k2)</tt>) must not throw a

 * <tt>ClassCastException</tt> for any keys <tt>k1</tt> and <tt>k2</tt> in

 * the sorted map.  Attempts to violate this restriction will cause the

 * offending method or constructor invocation to throw a

 * <tt>ClassCastException</tt>.

 *

 * <p>Note that the ordering maintained by a sorted map (whether or not an

 * explicit comparator is provided) must be <i>consistent with equals</i> if

 * the sorted map is to correctly implement the <tt>Map</tt> interface.  (See

 * the <tt>Comparable</tt> interface or <tt>Comparator</tt> interface for a

 * precise definition of <i>consistent with equals</i>.)  This is so because

 * the <tt>Map</tt> interface is defined in terms of the <tt>equals</tt>

 * operation, but a sorted map performs all key comparisons using its

 * <tt>compareTo</tt> (or <tt>compare</tt>) 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 <i>is</i> well-defined even if its

 * ordering is inconsistent with equals; it just fails to obey the general

 * contract of the <tt>Map</tt> interface.

 *

 * <p>All general-purpose sorted map implementation classes should

 * provide four "standard" constructors: 1) A void (no arguments)

 * constructor, which creates an empty sorted map sorted according to

 * the natural ordering of its keys.  2) A constructor with a

 * single argument of type <tt>Comparator</tt>, which creates an empty

 * sorted map sorted according to the specified comparator.  3) A

 * constructor with a single argument of type <tt>Map</tt>, which

 * creates a new map with the same key-value mappings as its argument,

 * sorted according to the keys' natural ordering.  4) A constructor

 * with a single argument of type <tt>SortedMap</tt>,

 * which creates a new sorted map with the same key-value mappings and

 * the same ordering as the input sorted map.  There is no way to

 * enforce this recommendation, as interfaces cannot contain

 * constructors.

 *

 * <p>Note: several methods return submaps with restricted key ranges.

 * Such ranges are <i>half-open</i>, that is, they include their low

 * endpoint but not their high endpoint (where applicable).  If you need a

 * <i>closed range</i> (which includes both endpoints), and the key type

 * allows for calculation of the successor of a given key, merely request

 * the subrange from <tt>lowEndpoint</tt> to

 * <tt>successor(highEndpoint)</tt>.  For example, suppose that <tt>m</tt>

 * is a map whose keys are strings.  The following idiom obtains a view

 * containing all of the key-value mappings in <tt>m</tt> whose keys are

 * between <tt>low</tt> and <tt>high</tt>, inclusive:<pre>

 *   SortedMap&lt;String, V&gt; sub = m.subMap(low, high+"\0");</pre>

 *

 * A similar technique can be used to generate an <i>open range</i>

 * (which contains neither endpoint).  The following idiom obtains a

 * view containing all of the key-value mappings in <tt>m</tt> whose keys

 * are between <tt>low</tt> and <tt>high</tt>, 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

     * <tt>null</tt> if this map uses the {@linkplain Comparable

     * natural ordering} of its keys.

     *

     * @return the comparator used to order the keys in this map,

     *         or <tt>null</tt> 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

     * <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive.  (If

     * <tt>fromKey</tt> and <tt>toKey</tt> 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 <tt>IllegalArgumentException</tt>

     * 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

     *         <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive

     * @throws ClassCastException if <tt>fromKey</tt> and <tt>toKey</tt>

     *         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 <tt>fromKey</tt> or <tt>toKey</tt>

     *         cannot be compared to keys currently in the map.

     * @throws NullPointerException if <tt>fromKey</tt> or <tt>toKey</tt>

     *         is null and this map does not permit null keys

     * @throws IllegalArgumentException if <tt>fromKey</tt> is greater than

     *         <tt>toKey</tt>; or if this map itself has a restricted

     *         range, and <tt>fromKey</tt> or <tt>toKey</tt> 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 <tt>toKey</tt>.  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 <tt>IllegalArgumentException</tt>

     * 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 <tt>toKey</tt>

     * @throws ClassCastException if <tt>toKey</tt> is not compatible

     *         with this map's comparator (or, if the map has no comparator,

     *         if <tt>toKey</tt> does not implement {@link Comparable}).

     *         Implementations may, but are not required to, throw this

     *         exception if <tt>toKey</tt> cannot be compared to keys

     *         currently in the map.

     * @throws NullPointerException if <tt>toKey</tt> is null and

     *         this map does not permit null keys

     * @throws IllegalArgumentException if this map itself has a

     *         restricted range, and <tt>toKey</tt> 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 <tt>fromKey</tt>.  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 <tt>IllegalArgumentException</tt>

     * 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 <tt>fromKey</tt>

     * @throws ClassCastException if <tt>fromKey</tt> is not compatible

     *         with this map's comparator (or, if the map has no comparator,

     *         if <tt>fromKey</tt> does not implement {@link Comparable}).

     *         Implementations may, but are not required to, throw this

     *         exception if <tt>fromKey</tt> cannot be compared to keys

     *         currently in the map.

     * @throws NullPointerException if <tt>fromKey</tt> is null and

     *         this map does not permit null keys

     * @throws IllegalArgumentException if this map itself has a

     *         restricted range, and <tt>fromKey</tt> 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 <tt>remove</tt> operation), the results of

     * the iteration are undefined.  The set supports element removal,

     * which removes the corresponding mapping from the map, via the

     * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,

     * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>

     * operations.  It does not support the <tt>add</tt> or <tt>addAll</tt>

     * 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 <tt>remove</tt> operation),

     * the results of the iteration are undefined.  The collection

     * supports element removal, which removes the corresponding

     * mapping from the map, via the <tt>Iterator.remove</tt>,

     * <tt>Collection.remove</tt>, <tt>removeAll</tt>,

     * <tt>retainAll</tt> and <tt>clear</tt> operations.  It does not

     * support the <tt>add</tt> or <tt>addAll</tt> 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 <tt>remove</tt> operation, or through the

     * <tt>setValue</tt> 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 <tt>Iterator.remove</tt>,

     * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and

     * <tt>clear</tt> operations.  It does not support the

     * <tt>add</tt> or <tt>addAll</tt> operations.

     *

     * @return a set view of the mappings contained in this map,

     *         sorted in ascending key order

     */

    Set<Map.Entry<K, V>> entrySet();

}