1. /*

  2.  * @(#)SortedMap.java	1.12 00/02/02

  3.  *

  4.  * Copyright 1998-2000 Sun Microsystems, Inc. All Rights Reserved.

  5.  * 

  6.  * This software is the proprietary information of Sun Microsystems, Inc.  

  7.  * Use is subject to license terms.

  8.  * 

  9.  */

  10. 

  11. package java.util;

  12. 

  13. /**

  14.  * A map that further guarantees that it will be in ascending key order,

  15.  * sorted according to the <i>natural ordering</i> of its keys (see the

  16.  * <tt>Comparable</tt> interface), or by a comparator provided at sorted map

  17.  * creation time.  This order is reflected when iterating over the sorted

  18.  * map's collection views (returned by the <tt>entrySet</tt>, <tt>keySet</tt>

  19.  * and <tt>values</tt> methods).  Several additional operations are provided

  20.  * to take advantage of the ordering.  (This interface is the map analogue of

  21.  * the <tt>SortedSet</tt> interface.)<p>

  22.  *

  23.  * All keys inserted into a sorted map must implement the <tt>Comparable</tt>

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

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

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

  27.  * <tt>ClassCastException</tt> for any elements <tt>k1</tt> and <tt>k2</tt> in

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

  29.  * offending method or constructor invocation to throw a

  30.  * <tt>ClassCastException</tt>.<p>

  31.  *

  32.  * Note that the ordering maintained by a sorted map (whether or not an

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

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

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

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

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

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

  39.  * <tt>compareTo</tt> (or <tt>compare</tt>) method, so two keys that are

  40.  * deemed equal by this method are, from the standpoint of the sorted map,

  41.  * equal.  The behavior of a tree map <i>is</i> well-defined even if its

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

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

  44.  *

  45.  * All general-purpose sorted map implementation classes should provide four

  46.  * "standard" constructors: 1) A void (no arguments) constructor, which

  47.  * creates an empty sorted map sorted according to the <i>natural order</i> of

  48.  * its keys.  2) A constructor with a single argument of type

  49.  * <tt>Comparator</tt>, which creates an empty sorted map sorted according to

  50.  * the specified comparator.  3) A constructor with a single argument of type

  51.  * <tt>Map</tt>, which creates a new map with the same key-value mappings as

  52.  * its argument, sorted according to the keys' natural ordering.  4) A

  53.  * constructor with a single argument of type sorted map, which creates a new

  54.  * sorted map with the same key-value mappings and the same ordering as the

  55.  * input sorted map.  There is no way to enforce this recommendation (as

  56.  * interfaces cannot contain constructors) but the SDK implementation

  57.  * (TreeMap) complies.

  58.  *

  59.  * @author  Josh Bloch

  60.  * @version 1.12, 02/02/00

  61.  * @see Map

  62.  * @see TreeMap

  63.  * @see SortedSet

  64.  * @see Comparator

  65.  * @see Comparable

  66.  * @see Collection

  67.  * @see ClassCastException

  68.  * @since 1.2

  69.  */

  70. 

  71. public interface SortedMap extends Map {

  72.     /**

  73.      * Returns the comparator associated with this sorted map, or

  74.      * <tt>null</tt> if it uses its keys' natural ordering.

  75.      *

  76.      * @return the comparator associated with this sorted map, or

  77.      * 	       <tt>null</tt> if it uses its keys' natural ordering.

  78.      */

  79.     Comparator comparator();

  80. 

  81.     /**

  82.      * Returns a view of the portion of this sorted map whose keys range from

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

  84.      * <tt>fromKey</tt> and <tt>toKey</tt> are equal, the returned sorted map

  85.      * is empty.)  The returned sorted map is backed by this sorted map, so

  86.      * changes in the returned sorted map are reflected in this sorted map,

  87.      * and vice-versa.  The returned Map supports all optional map operations

  88.      * that this sorted map supports.<p>

  89.      *

  90.      * The map returned by this method will throw an

  91.      * <tt>IllegalArgumentException</tt> if the user attempts to insert a key

  92.      * outside the specified range.<p>

  93.      *

  94.      * Note: this method always returns a <i>half-open range</i> (which

  95.      * includes its low endpoint but not its high endpoint).  If you need a

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

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

  98.      * subrange from <tt>lowEndpoint</tt> to <tt>successor(highEndpoint)</tt>.

  99.      * For example, suppose that <tt>m</tt> is a map whose keys are strings.

  100.      * The following idiom obtains a view containing all of the key-value

  101.      * mappings in <tt>m</tt> whose keys are between <tt>low</tt> and

  102.      * <tt>high</tt>, inclusive:

  103.      * 

  104.      * 	    <pre>    Map sub = m.subMap(low, high+"\0");</pre>

  105.      * 

  106.      * A similarly technique can be used to generate an <i>open range</i>

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

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

  109.      * are between <tt>low</tt> and <tt>high</tt>, exclusive:

  110.      * 

  111.      * 	    <pre>    Map sub = m.subMap(low+"\0", high);</pre>

  112.      *

  113.      * @param fromKey low endpoint (inclusive) of the subMap.

  114.      * @param toKey high endpoint (exclusive) of the subMap.

  115.      * @return a view of the specified range within this sorted map.

  116.      * 

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

  118.      *         cannot be compared to one another using this map's comparator

  119.      *         (or, if the map has no comparator, using natural ordering).

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

  121.      *	       exception if <tt>fromKey</tt> or <tt>toKey</tt>

  122.      *         cannot be compared to keys currently in the map.

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

  124.      *         <tt>toKey</tt> or if this map is itself a subMap, headMap,

  125.      *         or tailMap, and <tt>fromKey</tt> or <tt>toKey</tt> are not

  126.      *         within the specified range of the subMap, headMap, or tailMap.

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

  128.      *	       <tt>null</tt> and this sorted map does not tolerate

  129.      *	       <tt>null</tt> keys.

  130.      */

  131.     SortedMap subMap(Object fromKey, Object toKey);

  132. 

  133.     /**

  134.      * Returns a view of the portion of this sorted map whose keys are

  135.      * strictly less than toKey.  The returned sorted map is backed by this

  136.      * sorted map, so changes in the returned sorted map are reflected in this

  137.      * sorted map, and vice-versa.  The returned map supports all optional map

  138.      * operations that this sorted map supports.<p>

  139.      *

  140.      * The map returned by this method will throw an IllegalArgumentException

  141.      * if the user attempts to insert a key outside the specified range.<p>

  142.      *

  143.      * Note: this method always returns a view that does not contain its

  144.      * (high) endpoint.  If you need a view that does contain this endpoint,

  145.      * and the key type allows for calculation of the successor a given

  146.      * key, merely request a headMap bounded by successor(highEndpoint).

  147.      * For example, suppose that suppose that <tt>m</tt> is a map whose keys

  148.      * are strings.  The following idiom obtains a view containing all of the

  149.      * key-value mappings in <tt>m</tt> whose keys are less than or equal to

  150.      * <tt>high</tt>:

  151.      * 

  152.      * 	    <pre>    Map head = m.headMap(high+"\0");</pre>

  153.      *

  154.      * @param toKey high endpoint (exclusive) of the subMap.

  155.      * @return a view of the specified initial range of this sorted map.

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

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

  158.      *         if <tt>toKey</tt> does not implement <tt>Comparable</tt>).

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

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

  161.      *         currently in the map.

  162.      * @throws IllegalArgumentException if this map is itself a subMap,

  163.      *         headMap, or tailMap, and <tt>toKey</tt> is not within the

  164.      *         specified range of the subMap, headMap, or tailMap.

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

  166.      *	       this sorted map does not tolerate <tt>null</tt> keys.

  167.      */

  168.     SortedMap headMap(Object toKey);

  169. 

  170.     /**

  171.      * Returns a view of the portion of this sorted map whose keys are greater

  172.      * than or equal to <tt>fromKey</tt>.  The returned sorted map is backed

  173.      * by this sorted map, so changes in the returned sorted map are reflected

  174.      * in this sorted map, and vice-versa.  The returned map supports all

  175.      * optional map operations that this sorted map supports.<p>

  176.      *

  177.      * The map returned by this method will throw an

  178.      * <tt>IllegalArgumentException</tt> if the user attempts to insert a key

  179.      * outside the specified range.<p>

  180.      *

  181.      * Note: this method always returns a view that contains its (low)

  182.      * endpoint.  If you need a view that does not contain this endpoint, and

  183.      * the element type allows for calculation of the successor a given value,

  184.      * merely request a tailMap bounded by <tt>successor(lowEndpoint)</tt>.

  185.      * For example, suppose that suppose that <tt>m</tt> is a map whose keys

  186.      * are strings.  The following idiom obtains a view containing all of the

  187.      * key-value mappings in <tt>m</tt> whose keys are strictly greater than

  188.      * <tt>low</tt>:

  189.      * 

  190.      * 	    <pre>    Map tail = m.tailMap(low+"\0");</pre>

  191.      *

  192.      * @param fromKey low endpoint (inclusive) of the tailMap.

  193.      * @return a view of the specified final range of this sorted map.

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

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

  196.      *         if <tt>fromKey</tt> does not implement <tt>Comparable</tt>).

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

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

  199.      *         currently in the map.

  200.      * @throws IllegalArgumentException if this map is itself a subMap,

  201.      *         headMap, or tailMap, and <tt>fromKey</tt> is not within the

  202.      *         specified range of the subMap, headMap, or tailMap.

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

  204.      *	       this sorted map does not tolerate <tt>null</tt> keys.

  205.      */

  206.     SortedMap tailMap(Object fromKey);

  207. 

  208.     /**

  209.      * Returns the first (lowest) key currently in this sorted map.

  210.      *

  211.      * @return the first (lowest) key currently in this sorted map.

  212.      * @throws    NoSuchElementException if this map is empty.

  213.      */

  214.     Object firstKey();

  215. 

  216.     /**

  217.      * Returns the last (highest) key currently in this sorted map.

  218.      *

  219.      * @return the last (highest) key currently in this sorted map.

  220.      * @throws     NoSuchElementException if this map is empty.

  221.      */

  222.     Object lastKey();

  223. }