java/util/NavigableMap.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/licenses/publicdomain
 */

package java.util;

/**
 * A {@link SortedMap} extended with navigation methods returning the
 * closest matches for given search targets. Methods
 * <tt>lowerEntry</tt>, <tt>floorEntry</tt>, <tt>ceilingEntry</tt>,
 * and <tt>higherEntry</tt> return <tt>Map.Entry</tt> objects
 * associated with keys respectively less than, less than or equal,
 * greater than or equal, and greater than a given key, returning
 * <tt>null</tt> if there is no such key.  Similarly, methods
 * <tt>lowerKey</tt>, <tt>floorKey</tt>, <tt>ceilingKey</tt>, and
 * <tt>higherKey</tt> return only the associated keys. All of these
 * methods are designed for locating, not traversing entries.
 *
 * <p>A <tt>NavigableMap</tt> may be viewed and traversed in either
 * ascending or descending key order.  The <tt>Map</tt> methods
 * <tt>keySet</tt> and <tt>entrySet</tt> return ascending views, and
 * the additional methods <tt>descendingKeySet</tt> and
 * <tt>descendingEntrySet</tt> return descending views. The
 * performance of ascending traversals is likely to be faster than
 * descending traversals.  Notice that it is possible to perform
 * subrange traversals in either direction using <tt>navigableSubMap</tt>.
 * Methods <tt>navigableSubMap</tt>, <tt>navigableHeadMap</tt>, and
 * <tt>navigableTailMap</tt> differ from the similarly named
 * <tt>SortedMap</tt> methods only in their declared return types.
 * Submaps of any <tt>NavigableMap</tt> must implement the
 * <tt>NavigableMap</tt> interface.
 *
 * <p>This interface additionally defines methods <tt>firstEntry</tt>,
 * <tt>pollFirstEntry</tt>, <tt>lastEntry</tt>, and
 * <tt>pollLastEntry</tt> that return and/or remove the least and
 * greatest mappings, if any exist, else returning <tt>null</tt>.
 *
 * <p> Implementations of entry-returning methods are expected to
 * return <tt>Map.Entry</tt> pairs representing snapshots of mappings
 * at the time they were produced, and thus generally do <em>not</em>
 * support the optional <tt>Entry.setValue</tt> method. Note however
 * that it is possible to change mappings in the associated map using
 * method <tt>put</tt>.
 *
 * <p>This interface is a member of the
 * <a href="{@docRoot}/../guide/collections/index.html">
 * Java Collections Framework</a>.
 *
 * @author Doug Lea
 * @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 <tt>null</tt> if there is
     * no such key.
     *
     * @param key the key
     * @return an entry with the greatest key less than <tt>key</tt>,
     *         or <tt>null</tt> 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
     * <tt>null</tt> if there is no such key.
     *
     * @param key the key
     * @return the greatest key less than <tt>key</tt>,
     *         or <tt>null</tt> 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 <tt>null</tt> if there
     * is no such key.
     *
     * @param key the key
     * @return an entry with the greatest key less than or equal to
     *         <tt>key</tt>, or <tt>null</tt> 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 <tt>null</tt> if there is no such key.
     *
     * @param key the key
     * @return the greatest key less than or equal to <tt>key</tt>,
     *         or <tt>null</tt> 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 <tt>null</tt> if
     * there is no such key.
     *
     * @param key the key
     * @return an entry with the least key greater than or equal to
     *         <tt>key</tt>, or <tt>null</tt> 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 <tt>null</tt> if there is no such key.
     *
     * @param key the key
     * @return the least key greater than or equal to <tt>key</tt>,
     *         or <tt>null</tt> 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 <tt>null</tt> if there
     * is no such key.
     *
     * @param key the key
     * @return an entry with the least key greater than <tt>key</tt>,
     *         or <tt>null</tt> 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
     * <tt>null</tt> if there is no such key.
     *
     * @param key the key
     * @return the least key greater than <tt>key</tt>,
     *         or <tt>null</tt> 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 <tt>null</tt> if the map is empty.
     *
     * @return an entry with the least key,
     *         or <tt>null</tt> if this map is empty
     */
    Map.Entry<K,V> firstEntry();

    /**
     * Returns a key-value mapping associated with the greatest
     * key in this map, or <tt>null</tt> if the map is empty.
     *
     * @return an entry with the greatest key,
     *         or <tt>null</tt> 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 <tt>null</tt> if the map is empty.
     *
     * @return the removed first entry of this map,
     *         or <tt>null</tt> 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 <tt>null</tt> if the map is empty.
     *
     * @return the removed last entry of this map,
     *         or <tt>null</tt> if this map is empty
     */
    Map.Entry<K,V> pollLastEntry();

    /**
     * Returns a {@link Set} 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 <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
     *         descending order
     */
    Set<K> descendingKeySet();

    /**
     * Returns a {@link Set} view of the mappings contained in this map.
     * The set's iterator returns the entries in descending 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 descending key order
     */
    Set<Map.Entry<K, V>> descendingEntrySet();

    /**
     * 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
     */
    NavigableMap<K,V> navigableSubMap(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
     */
    NavigableMap<K,V> navigableHeadMap(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
     */
    NavigableMap<K,V> navigableTailMap(K fromKey);
}
Revision:	1.13
Committed:	Mon Mar 27 18:23:13 2006 UTC (18 years, 1 month ago) by dl
Branch:	MAIN
Changes since 1.12:	+1 -1 lines
Log Message:	Bad tt tag
#	User	Rev	Content
1	dl	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/licenses/publicdomain
5			*/
6
7			package java.util;
8
9			/**
10			* A {@link SortedMap} extended with navigation methods returning the
11			* closest matches for given search targets. Methods
12			* <tt>lowerEntry</tt>, <tt>floorEntry</tt>, <tt>ceilingEntry</tt>,
13			* and <tt>higherEntry</tt> return <tt>Map.Entry</tt> objects
14			* associated with keys respectively less than, less than or equal,
15			* greater than or equal, and greater than a given key, returning
16			* <tt>null</tt> if there is no such key. Similarly, methods
17			* <tt>lowerKey</tt>, <tt>floorKey</tt>, <tt>ceilingKey</tt>, and
18			* <tt>higherKey</tt> return only the associated keys. All of these
19			* methods are designed for locating, not traversing entries.
20			*
21			* <p>A <tt>NavigableMap</tt> may be viewed and traversed in either
22			* ascending or descending key order. The <tt>Map</tt> methods
23			* <tt>keySet</tt> and <tt>entrySet</tt> return ascending views, and
24			* the additional methods <tt>descendingKeySet</tt> and
25			* <tt>descendingEntrySet</tt> return descending views. The
26			* performance of ascending traversals is likely to be faster than
27			* descending traversals. Notice that it is possible to perform
28	dl	1.4	* subrange traversals in either direction using <tt>navigableSubMap</tt>.
29			* Methods <tt>navigableSubMap</tt>, <tt>navigableHeadMap</tt>, and
30			* <tt>navigableTailMap</tt> differ from the similarly named
31	dl	1.10	* <tt>SortedMap</tt> methods only in their declared return types.
32	dl	1.13	* Submaps of any <tt>NavigableMap</tt> must implement the
33	jsr166	1.11	* <tt>NavigableMap</tt> interface.
34	jsr166	1.5	*
35	dl	1.1	* <p>This interface additionally defines methods <tt>firstEntry</tt>,
36			* <tt>pollFirstEntry</tt>, <tt>lastEntry</tt>, and
37			* <tt>pollLastEntry</tt> that return and/or remove the least and
38			* greatest mappings, if any exist, else returning <tt>null</tt>.
39			*
40			* <p> Implementations of entry-returning methods are expected to
41			* return <tt>Map.Entry</tt> pairs representing snapshots of mappings
42			* at the time they were produced, and thus generally do <em>not</em>
43			* support the optional <tt>Entry.setValue</tt> method. Note however
44			* that it is possible to change mappings in the associated map using
45			* method <tt>put</tt>.
46			*
47	jsr166	1.7	* <p>This interface is a member of the
48			* <a href="{@docRoot}/../guide/collections/index.html">
49			* Java Collections Framework</a>.
50			*
51	dl	1.1	* @author Doug Lea
52			* @param <K> the type of keys maintained by this map
53	jsr166	1.5	* @param <V> the type of mapped values
54	jsr166	1.6	* @since 1.6
55	dl	1.1	*/
56			public interface NavigableMap<K,V> extends SortedMap<K,V> {
57			/**
58	jsr166	1.8	* Returns a key-value mapping associated with the greatest key
59			* strictly less than the given key, or <tt>null</tt> if there is
60			* no such key.
61	jsr166	1.5	*
62	jsr166	1.8	* @param key the key
63			* @return an entry with the greatest key less than <tt>key</tt>,
64			* or <tt>null</tt> if there is no such key
65			* @throws ClassCastException if the specified key cannot be compared
66			* with the keys currently in the map
67			* @throws NullPointerException if the specified key is null
68			* and this map does not permit null keys
69	dl	1.1	*/
70	jsr166	1.8	Map.Entry<K,V> lowerEntry(K key);
71	dl	1.1
72			/**
73	jsr166	1.8	* Returns the greatest key strictly less than the given key, or
74	dl	1.1	* <tt>null</tt> if there is no such key.
75	jsr166	1.5	*
76	jsr166	1.8	* @param key the key
77			* @return the greatest key less than <tt>key</tt>,
78			* or <tt>null</tt> if there is no such key
79			* @throws ClassCastException if the specified key cannot be compared
80			* with the keys currently in the map
81			* @throws NullPointerException if the specified key is null
82			* and this map does not permit null keys
83	dl	1.1	*/
84	jsr166	1.8	K lowerKey(K key);
85	dl	1.1
86			/**
87	jsr166	1.8	* Returns a key-value mapping associated with the greatest key
88			* less than or equal to the given key, or <tt>null</tt> if there
89			* is no such key.
90	jsr166	1.5	*
91	jsr166	1.8	* @param key the key
92			* @return an entry with the greatest key less than or equal to
93			* <tt>key</tt>, or <tt>null</tt> if there is no such key
94			* @throws ClassCastException if the specified key cannot be compared
95			* with the keys currently in the map
96			* @throws NullPointerException if the specified key is null
97			* and this map does not permit null keys
98	dl	1.1	*/
99	jsr166	1.8	Map.Entry<K,V> floorEntry(K key);
100	dl	1.1
101			/**
102	jsr166	1.8	* Returns the greatest key less than or equal to the given key,
103			* or <tt>null</tt> if there is no such key.
104	jsr166	1.5	*
105	jsr166	1.8	* @param key the key
106			* @return the greatest key less than or equal to <tt>key</tt>,
107			* or <tt>null</tt> if there is no such key
108			* @throws ClassCastException if the specified key cannot be compared
109			* with the keys currently in the map
110			* @throws NullPointerException if the specified key is null
111			* and this map does not permit null keys
112	dl	1.1	*/
113	jsr166	1.8	K floorKey(K key);
114	dl	1.1
115			/**
116	jsr166	1.8	* Returns a key-value mapping associated with the least key
117			* greater than or equal to the given key, or <tt>null</tt> if
118			* there is no such key.
119	jsr166	1.5	*
120	jsr166	1.8	* @param key the key
121			* @return an entry with the least key greater than or equal to
122			* <tt>key</tt>, or <tt>null</tt> if there is no such key
123			* @throws ClassCastException if the specified key cannot be compared
124			* with the keys currently in the map
125			* @throws NullPointerException if the specified key is null
126			* and this map does not permit null keys
127	dl	1.1	*/
128	jsr166	1.8	Map.Entry<K,V> ceilingEntry(K key);
129	dl	1.1
130			/**
131	jsr166	1.8	* Returns the least key greater than or equal to the given key,
132			* or <tt>null</tt> if there is no such key.
133	jsr166	1.5	*
134	jsr166	1.8	* @param key the key
135			* @return the least key greater than or equal to <tt>key</tt>,
136			* or <tt>null</tt> if there is no such key
137			* @throws ClassCastException if the specified key cannot be compared
138			* with the keys currently in the map
139			* @throws NullPointerException if the specified key is null
140			* and this map does not permit null keys
141	dl	1.1	*/
142	jsr166	1.8	K ceilingKey(K key);
143	dl	1.1
144			/**
145			* Returns a key-value mapping associated with the least key
146			* strictly greater than the given key, or <tt>null</tt> if there
147	jsr166	1.8	* is no such key.
148	jsr166	1.5	*
149	jsr166	1.8	* @param key the key
150			* @return an entry with the least key greater than <tt>key</tt>,
151			* or <tt>null</tt> if there is no such key
152			* @throws ClassCastException if the specified key cannot be compared
153			* with the keys currently in the map
154			* @throws NullPointerException if the specified key is null
155			* and this map does not permit null keys
156	dl	1.1	*/
157	dl	1.3	Map.Entry<K,V> higherEntry(K key);
158	dl	1.1
159			/**
160			* Returns the least key strictly greater than the given key, or
161			* <tt>null</tt> if there is no such key.
162	jsr166	1.5	*
163	jsr166	1.8	* @param key the key
164			* @return the least key greater than <tt>key</tt>,
165			* or <tt>null</tt> if there is no such key
166			* @throws ClassCastException if the specified key cannot be compared
167			* with the keys currently in the map
168			* @throws NullPointerException if the specified key is null
169			* and this map does not permit null keys
170	dl	1.1	*/
171	dl	1.3	K higherKey(K key);
172	dl	1.1
173			/**
174			* Returns a key-value mapping associated with the least
175			* key in this map, or <tt>null</tt> if the map is empty.
176	jsr166	1.5	*
177	jsr166	1.8	* @return an entry with the least key,
178			* or <tt>null</tt> if this map is empty
179	dl	1.1	*/
180	dl	1.3	Map.Entry<K,V> firstEntry();
181	dl	1.1
182			/**
183			* Returns a key-value mapping associated with the greatest
184			* key in this map, or <tt>null</tt> if the map is empty.
185	jsr166	1.5	*
186	jsr166	1.8	* @return an entry with the greatest key,
187			* or <tt>null</tt> if this map is empty
188	dl	1.1	*/
189	dl	1.3	Map.Entry<K,V> lastEntry();
190	dl	1.1
191			/**
192			* Removes and returns a key-value mapping associated with
193			* the least key in this map, or <tt>null</tt> if the map is empty.
194	jsr166	1.5	*
195	jsr166	1.8	* @return the removed first entry of this map,
196			* or <tt>null</tt> if this map is empty
197	dl	1.1	*/
198	dl	1.3	Map.Entry<K,V> pollFirstEntry();
199	dl	1.1
200			/**
201			* Removes and returns a key-value mapping associated with
202			* the greatest key in this map, or <tt>null</tt> if the map is empty.
203	jsr166	1.5	*
204	jsr166	1.8	* @return the removed last entry of this map,
205			* or <tt>null</tt> if this map is empty
206	dl	1.1	*/
207	dl	1.3	Map.Entry<K,V> pollLastEntry();
208	dl	1.1
209			/**
210	jsr166	1.8	* Returns a {@link Set} view of the keys contained in this map.
211			* The set's iterator returns the keys in descending order.
212			* The set is backed by the map, so changes to the map are
213			* reflected in the set, and vice-versa. If the map is modified
214			* while an iteration over the set is in progress (except through
215			* the iterator's own <tt>remove</tt> operation), the results of
216			* the iteration are undefined. The set supports element removal,
217			* which removes the corresponding mapping from the map, via the
218			* <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
219	jsr166	1.9	* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
220			* operations. It does not support the <tt>add</tt> or <tt>addAll</tt>
221	dl	1.1	* operations.
222			*
223	jsr166	1.8	* @return a set view of the keys contained in this map, sorted in
224			* descending order
225	dl	1.1	*/
226			Set<K> descendingKeySet();
227
228			/**
229	jsr166	1.8	* Returns a {@link Set} view of the mappings contained in this map.
230			* The set's iterator returns the entries in descending key order.
231			* The set is backed by the map, so changes to the map are
232			* reflected in the set, and vice-versa. If the map is modified
233			* while an iteration over the set is in progress (except through
234			* the iterator's own <tt>remove</tt> operation, or through the
235			* <tt>setValue</tt> operation on a map entry returned by the
236			* iterator) the results of the iteration are undefined. The set
237			* supports element removal, which removes the corresponding
238			* mapping from the map, via the <tt>Iterator.remove</tt>,
239			* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
240			* <tt>clear</tt> operations. It does not support the
241			* <tt>add</tt> or <tt>addAll</tt> operations.
242	dl	1.1	*
243	jsr166	1.8	* @return a set view of the mappings contained in this map,
244			* sorted in descending key order
245	dl	1.1	*/
246			Set<Map.Entry<K, V>> descendingEntrySet();
247
248			/**
249			* Returns a view of the portion of this map whose keys range from
250			* <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive. (If
251	jsr166	1.8	* <tt>fromKey</tt> and <tt>toKey</tt> are equal, the returned map
252			* is empty.) The returned map is backed by this map, so changes
253			* in the returned map are reflected in this map, and vice-versa.
254			* The returned map supports all optional map operations that this
255			* map supports.
256	dl	1.3	*
257	jsr166	1.8	* <p>The returned map will throw an <tt>IllegalArgumentException</tt>
258			* on an attempt to insert a key outside its range.
259	dl	1.1	*
260	jsr166	1.8	* @param fromKey low endpoint (inclusive) of the keys in the returned map
261			* @param toKey high endpoint (exclusive) of the keys in the returned map
262	dl	1.1	* @return a view of the portion of this map whose keys range from
263	jsr166	1.8	* <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive
264			* @throws ClassCastException if <tt>fromKey</tt> and <tt>toKey</tt>
265			* cannot be compared to one another using this map's comparator
266			* (or, if the map has no comparator, using natural ordering).
267			* Implementations may, but are not required to, throw this
268			* exception if <tt>fromKey</tt> or <tt>toKey</tt>
269			* cannot be compared to keys currently in the map.
270			* @throws NullPointerException if <tt>fromKey</tt> or <tt>toKey</tt>
271			* is null and this map does not permit null keys
272			* @throws IllegalArgumentException if <tt>fromKey</tt> is greater than
273			* <tt>toKey</tt>; or if this map itself has a restricted
274			* range, and <tt>fromKey</tt> or <tt>toKey</tt> lies
275			* outside the bounds of the range
276	dl	1.1	*/
277	dl	1.3	NavigableMap<K,V> navigableSubMap(K fromKey, K toKey);
278	dl	1.1
279			/**
280	jsr166	1.8	* Returns a view of the portion of this map whose keys are
281			* strictly less than <tt>toKey</tt>. The returned map is backed
282			* by this map, so changes in the returned map are reflected in
283			* this map, and vice-versa. The returned map supports all
284			* optional map operations that this map supports.
285			*
286			* <p>The returned map will throw an <tt>IllegalArgumentException</tt>
287			* on an attempt to insert a key outside its range.
288			*
289			* @param toKey high endpoint (exclusive) of the keys in the returned map
290	dl	1.1	* @return a view of the portion of this map whose keys are strictly
291	jsr166	1.8	* less than <tt>toKey</tt>
292	dl	1.1	* @throws ClassCastException if <tt>toKey</tt> is not compatible
293			* with this map's comparator (or, if the map has no comparator,
294	jsr166	1.8	* if <tt>toKey</tt> does not implement {@link Comparable}).
295			* Implementations may, but are not required to, throw this
296			* exception if <tt>toKey</tt> cannot be compared to keys
297			* currently in the map.
298			* @throws NullPointerException if <tt>toKey</tt> is null
299			* and this map does not permit null keys
300			* @throws IllegalArgumentException if this map itself has a
301			* restricted range, and <tt>toKey</tt> lies outside the
302			* bounds of the range
303	dl	1.1	*/
304	dl	1.3	NavigableMap<K,V> navigableHeadMap(K toKey);
305	dl	1.1
306			/**
307			* Returns a view of the portion of this map whose keys are
308	jsr166	1.8	* greater than or equal to <tt>fromKey</tt>. The returned map is
309			* backed by this map, so changes in the returned map are
310			* reflected in this map, and vice-versa. The returned map
311			* supports all optional map operations that this map supports.
312			*
313			* <p>The returned map will throw an <tt>IllegalArgumentException</tt>
314			* on an attempt to insert a key outside its range.
315			*
316			* @param fromKey low endpoint (inclusive) of the keys in the returned map
317	dl	1.1	* @return a view of the portion of this map whose keys are greater
318	jsr166	1.8	* than or equal to <tt>fromKey</tt>
319	dl	1.1	* @throws ClassCastException if <tt>fromKey</tt> is not compatible
320			* with this map's comparator (or, if the map has no comparator,
321	jsr166	1.8	* if <tt>fromKey</tt> does not implement {@link Comparable}).
322			* Implementations may, but are not required to, throw this
323			* exception if <tt>fromKey</tt> cannot be compared to keys
324			* currently in the map.
325			* @throws NullPointerException if <tt>fromKey</tt> is null
326			* and this map does not permit null keys
327			* @throws IllegalArgumentException if this map itself has a
328			* restricted range, and <tt>fromKey</tt> lies outside the
329			* bounds of the range
330	dl	1.1	*/
331	jsr166	1.8	NavigableMap<K,V> navigableTailMap(K fromKey);
332	dl	1.1	}