1. /*

  2.  * @(#)SortedMap.java	1.8 01/11/29

  3.  *

  4.  * Copyright 2002 Sun Microsystems, Inc. All rights reserved.

  5.  * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.

  6.  */

  7. 

  8. package java.util;

  9. 

  10. /**

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

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

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

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

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

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

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

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

  19.  *

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

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

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

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

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

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

  26.  * offending method or constructor invocation to throw a

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

  28.  *

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

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

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

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

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

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

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

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

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

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

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

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

  41.  *

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

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

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

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

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

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

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

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

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

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

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

  53.  * interfaces cannot contain constructors) but the JDK implementation

  54.  * (TreeMap) complies.

  55.  *

  56.  * @author  Josh Bloch

  57.  * @version 1.8 11/29/01

  58.  * @see Map

  59.  * @see TreeMap

  60.  * @see SortedSet

  61.  * @see Comparator

  62.  * @see Comparable

  63.  * @see Collection

  64.  * @see ClassCastException

  65.  * @since JDK1.2

  66.  */

  67. 

  68. public interface SortedMap extends Map {

  69.     /**

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

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

  72.      *

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

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

  75.      */

  76.     Comparator comparator();

  77. 

  78.     /**

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

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

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

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

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

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

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

  86.      *

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

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

  89.      * outside the specified range.<p>

  90.      *

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

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

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

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

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

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

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

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

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

  100.      * 

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

  102.      * 

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

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

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

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

  107.      * 

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

  109.      *

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

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

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

  113.      * 

  114.      * @throws ClassCastException if <tt>fromKey</tt> or <tt>toKey</tt> cannot

  115.      *		  be compared with the keys currently in the sorted map.

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

  117.      *		  exception under these circumstances.)

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

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

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

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

  122.      *         <tt>toKey</tt>.

  123.      */

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

  125. 

  126.     /**

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

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

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

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

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

  132.      *

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

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

  135.      *

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

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

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

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

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

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

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

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

  144.      * 

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

  146.      *

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

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

  149.      * 

  150.      * @throws ClassCastException if <tt>toKey</tt> cannot be compared with

  151.      *		  the keys currently in the sorted map.  (Implementations may,

  152.      *		  but are not required to, throw this exception under these

  153.      *		  circumstances.)

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

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

  156.      */

  157.     SortedMap headMap(Object toKey);

  158. 

  159.     /**

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

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

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

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

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

  165.      *

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

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

  168.      * outside the specified range.<p>

  169.      *

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

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

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

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

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

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

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

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

  178.      * 

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

  180.      *

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

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

  183.      * 

  184.      * @throws ClassCastException if <tt>fromKey</tt> cannot be compared with

  185.      *		  the keys currently in the sorted map.  (Implementations may,

  186.      *		  but are not required to, throw this exception under these

  187.      *		  circumstances.)

  188.      * 

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

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

  191.      */

  192.     SortedMap tailMap(Object fromKey);

  193. 

  194.     /**

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

  196.      *

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

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

  199.      */

  200.     Object firstKey();

  201. 

  202.     /**

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

  204.      *

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

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

  207.      */

  208.     Object lastKey();

  209. }