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 that the returned maps
 * are guaranteed to obey 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 add 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:	1.8
Committed:	Mon May 16 06:27:52 2005 UTC (18 years, 11 months ago) by jsr166
Branch:	MAIN
Changes since 1.7:	+173 -146 lines
Log Message:	doc fixes
#	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			* <tt>SortedMap</tt> methods only in that the returned maps
32			* are guaranteed to obey the <tt>NavigableMap</tt> interface.
33	jsr166	1.5	*
34	dl	1.1	* <p>This interface additionally defines methods <tt>firstEntry</tt>,
35			* <tt>pollFirstEntry</tt>, <tt>lastEntry</tt>, and
36			* <tt>pollLastEntry</tt> that return and/or remove the least and
37			* greatest mappings, if any exist, else returning <tt>null</tt>.
38			*
39			* <p> Implementations of entry-returning methods are expected to
40			* return <tt>Map.Entry</tt> pairs representing snapshots of mappings
41			* at the time they were produced, and thus generally do <em>not</em>
42			* support the optional <tt>Entry.setValue</tt> method. Note however
43			* that it is possible to change mappings in the associated map using
44			* method <tt>put</tt>.
45			*
46	jsr166	1.7	* <p>This interface is a member of the
47			* <a href="{@docRoot}/../guide/collections/index.html">
48			* Java Collections Framework</a>.
49			*
50	dl	1.1	* @author Doug Lea
51			* @param <K> the type of keys maintained by this map
52	jsr166	1.5	* @param <V> the type of mapped values
53	jsr166	1.6	* @since 1.6
54	dl	1.1	*/
55			public interface NavigableMap<K,V> extends SortedMap<K,V> {
56			/**
57	jsr166	1.8	* Returns a key-value mapping associated with the greatest key
58			* strictly less than the given key, or <tt>null</tt> if there is
59			* no such key.
60	jsr166	1.5	*
61	jsr166	1.8	* @param key the key
62			* @return an entry with the greatest key less than <tt>key</tt>,
63			* or <tt>null</tt> if there is no such key
64			* @throws ClassCastException if the specified key cannot be compared
65			* with the keys currently in the map
66			* @throws NullPointerException if the specified key is null
67			* and this map does not permit null keys
68	dl	1.1	*/
69	jsr166	1.8	Map.Entry<K,V> lowerEntry(K key);
70	dl	1.1
71			/**
72	jsr166	1.8	* Returns the greatest key strictly less than the given key, or
73	dl	1.1	* <tt>null</tt> if there is no such key.
74	jsr166	1.5	*
75	jsr166	1.8	* @param key the key
76			* @return the greatest key less than <tt>key</tt>,
77			* or <tt>null</tt> if there is no such key
78			* @throws ClassCastException if the specified key cannot be compared
79			* with the keys currently in the map
80			* @throws NullPointerException if the specified key is null
81			* and this map does not permit null keys
82	dl	1.1	*/
83	jsr166	1.8	K lowerKey(K key);
84	dl	1.1
85			/**
86	jsr166	1.8	* Returns a key-value mapping associated with the greatest key
87			* less than or equal to the given key, or <tt>null</tt> if there
88			* is no such key.
89	jsr166	1.5	*
90	jsr166	1.8	* @param key the key
91			* @return an entry with the greatest key less than or equal to
92			* <tt>key</tt>, or <tt>null</tt> if there is no such key
93			* @throws ClassCastException if the specified key cannot be compared
94			* with the keys currently in the map
95			* @throws NullPointerException if the specified key is null
96			* and this map does not permit null keys
97	dl	1.1	*/
98	jsr166	1.8	Map.Entry<K,V> floorEntry(K key);
99	dl	1.1
100			/**
101	jsr166	1.8	* Returns the greatest key less than or equal to the given key,
102			* or <tt>null</tt> if there is no such key.
103	jsr166	1.5	*
104	jsr166	1.8	* @param key the key
105			* @return the greatest key less than or equal to <tt>key</tt>,
106			* or <tt>null</tt> if there is no such key
107			* @throws ClassCastException if the specified key cannot be compared
108			* with the keys currently in the map
109			* @throws NullPointerException if the specified key is null
110			* and this map does not permit null keys
111	dl	1.1	*/
112	jsr166	1.8	K floorKey(K key);
113	dl	1.1
114			/**
115	jsr166	1.8	* Returns a key-value mapping associated with the least key
116			* greater than or equal to the given key, or <tt>null</tt> if
117			* there is no such key.
118	jsr166	1.5	*
119	jsr166	1.8	* @param key the key
120			* @return an entry with the least key greater than or equal to
121			* <tt>key</tt>, or <tt>null</tt> if there is no such key
122			* @throws ClassCastException if the specified key cannot be compared
123			* with the keys currently in the map
124			* @throws NullPointerException if the specified key is null
125			* and this map does not permit null keys
126	dl	1.1	*/
127	jsr166	1.8	Map.Entry<K,V> ceilingEntry(K key);
128	dl	1.1
129			/**
130	jsr166	1.8	* Returns the least key greater than or equal to the given key,
131			* or <tt>null</tt> if there is no such key.
132	jsr166	1.5	*
133	jsr166	1.8	* @param key the key
134			* @return the least key greater than or equal to <tt>key</tt>,
135			* or <tt>null</tt> if there is no such key
136			* @throws ClassCastException if the specified key cannot be compared
137			* with the keys currently in the map
138			* @throws NullPointerException if the specified key is null
139			* and this map does not permit null keys
140	dl	1.1	*/
141	jsr166	1.8	K ceilingKey(K key);
142	dl	1.1
143			/**
144			* Returns a key-value mapping associated with the least key
145			* strictly greater than the given key, or <tt>null</tt> if there
146	jsr166	1.8	* is no such key.
147	jsr166	1.5	*
148	jsr166	1.8	* @param key the key
149			* @return an entry with the least key greater than <tt>key</tt>,
150			* or <tt>null</tt> if there is no such key
151			* @throws ClassCastException if the specified key cannot be compared
152			* with the keys currently in the map
153			* @throws NullPointerException if the specified key is null
154			* and this map does not permit null keys
155	dl	1.1	*/
156	dl	1.3	Map.Entry<K,V> higherEntry(K key);
157	dl	1.1
158			/**
159			* Returns the least key strictly greater than the given key, or
160			* <tt>null</tt> if there is no such key.
161	jsr166	1.5	*
162	jsr166	1.8	* @param key the key
163			* @return the least key greater than <tt>key</tt>,
164			* or <tt>null</tt> if there is no such key
165			* @throws ClassCastException if the specified key cannot be compared
166			* with the keys currently in the map
167			* @throws NullPointerException if the specified key is null
168			* and this map does not permit null keys
169	dl	1.1	*/
170	dl	1.3	K higherKey(K key);
171	dl	1.1
172			/**
173			* Returns a key-value mapping associated with the least
174			* key in this map, or <tt>null</tt> if the map is empty.
175	jsr166	1.5	*
176	jsr166	1.8	* @return an entry with the least key,
177			* or <tt>null</tt> if this map is empty
178	dl	1.1	*/
179	dl	1.3	Map.Entry<K,V> firstEntry();
180	dl	1.1
181			/**
182			* Returns a key-value mapping associated with the greatest
183			* key in this map, or <tt>null</tt> if the map is empty.
184	jsr166	1.5	*
185	jsr166	1.8	* @return an entry with the greatest key,
186			* or <tt>null</tt> if this map is empty
187	dl	1.1	*/
188	dl	1.3	Map.Entry<K,V> lastEntry();
189	dl	1.1
190			/**
191			* Removes and returns a key-value mapping associated with
192			* the least key in this map, or <tt>null</tt> if the map is empty.
193	jsr166	1.5	*
194	jsr166	1.8	* @return the removed first entry of this map,
195			* or <tt>null</tt> if this map is empty
196	dl	1.1	*/
197	dl	1.3	Map.Entry<K,V> pollFirstEntry();
198	dl	1.1
199			/**
200			* Removes and returns a key-value mapping associated with
201			* the greatest key in this map, or <tt>null</tt> if the map is empty.
202	jsr166	1.5	*
203	jsr166	1.8	* @return the removed last entry of this map,
204			* or <tt>null</tt> if this map is empty
205	dl	1.1	*/
206	dl	1.3	Map.Entry<K,V> pollLastEntry();
207	dl	1.1
208			/**
209	jsr166	1.8	* Returns a {@link Set} view of the keys contained in this map.
210			* The set's iterator returns the keys in descending order.
211			* The set is backed by the map, so changes to the map are
212			* reflected in the set, and vice-versa. If the map is modified
213			* while an iteration over the set is in progress (except through
214			* the iterator's own <tt>remove</tt> operation), the results of
215			* the iteration are undefined. The set supports element removal,
216			* which removes the corresponding mapping from the map, via the
217			* <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
218	dl	1.1	* <tt>removeAll</tt> <tt>retainAll</tt>, and <tt>clear</tt>
219			* operations. It does not support the add or <tt>addAll</tt>
220			* operations.
221			*
222	jsr166	1.8	* @return a set view of the keys contained in this map, sorted in
223			* descending order
224	dl	1.1	*/
225			Set<K> descendingKeySet();
226
227			/**
228	jsr166	1.8	* Returns a {@link Set} view of the mappings contained in this map.
229			* The set's iterator returns the entries in descending key order.
230			* The set is backed by the map, so changes to the map are
231			* reflected in the set, and vice-versa. If the map is modified
232			* while an iteration over the set is in progress (except through
233			* the iterator's own <tt>remove</tt> operation, or through the
234			* <tt>setValue</tt> operation on a map entry returned by the
235			* iterator) the results of the iteration are undefined. The set
236			* supports element removal, which removes the corresponding
237			* mapping from the map, via the <tt>Iterator.remove</tt>,
238			* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
239			* <tt>clear</tt> operations. It does not support the
240			* <tt>add</tt> or <tt>addAll</tt> operations.
241	dl	1.1	*
242	jsr166	1.8	* @return a set view of the mappings contained in this map,
243			* sorted in descending key order
244	dl	1.1	*/
245			Set<Map.Entry<K, V>> descendingEntrySet();
246
247			/**
248			* Returns a view of the portion of this map whose keys range from
249			* <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive. (If
250	jsr166	1.8	* <tt>fromKey</tt> and <tt>toKey</tt> are equal, the returned map
251			* is empty.) The returned map is backed by this map, so changes
252			* in the returned map are reflected in this map, and vice-versa.
253			* The returned map supports all optional map operations that this
254			* map supports.
255	dl	1.3	*
256	jsr166	1.8	* <p>The returned map will throw an <tt>IllegalArgumentException</tt>
257			* on an attempt to insert a key outside its range.
258	dl	1.1	*
259	jsr166	1.8	* @param fromKey low endpoint (inclusive) of the keys in the returned map
260			* @param toKey high endpoint (exclusive) of the keys in the returned map
261	dl	1.1	* @return a view of the portion of this map whose keys range from
262	jsr166	1.8	* <tt>fromKey</tt>, inclusive, to <tt>toKey</tt>, exclusive
263			* @throws ClassCastException if <tt>fromKey</tt> and <tt>toKey</tt>
264			* cannot be compared to one another using this map's comparator
265			* (or, if the map has no comparator, using natural ordering).
266			* Implementations may, but are not required to, throw this
267			* exception if <tt>fromKey</tt> or <tt>toKey</tt>
268			* cannot be compared to keys currently in the map.
269			* @throws NullPointerException if <tt>fromKey</tt> or <tt>toKey</tt>
270			* is null and this map does not permit null keys
271			* @throws IllegalArgumentException if <tt>fromKey</tt> is greater than
272			* <tt>toKey</tt>; or if this map itself has a restricted
273			* range, and <tt>fromKey</tt> or <tt>toKey</tt> lies
274			* outside the bounds of the range
275	dl	1.1	*/
276	dl	1.3	NavigableMap<K,V> navigableSubMap(K fromKey, K toKey);
277	dl	1.1
278			/**
279	jsr166	1.8	* Returns a view of the portion of this map whose keys are
280			* strictly less than <tt>toKey</tt>. The returned map is backed
281			* by this map, so changes in the returned map are reflected in
282			* this map, and vice-versa. The returned map supports all
283			* optional map operations that this map supports.
284			*
285			* <p>The returned map will throw an <tt>IllegalArgumentException</tt>
286			* on an attempt to insert a key outside its range.
287			*
288			* @param toKey high endpoint (exclusive) of the keys in the returned map
289	dl	1.1	* @return a view of the portion of this map whose keys are strictly
290	jsr166	1.8	* less than <tt>toKey</tt>
291	dl	1.1	* @throws ClassCastException if <tt>toKey</tt> is not compatible
292			* with this map's comparator (or, if the map has no comparator,
293	jsr166	1.8	* if <tt>toKey</tt> does not implement {@link Comparable}).
294			* Implementations may, but are not required to, throw this
295			* exception if <tt>toKey</tt> cannot be compared to keys
296			* currently in the map.
297			* @throws NullPointerException if <tt>toKey</tt> is null
298			* and this map does not permit null keys
299			* @throws IllegalArgumentException if this map itself has a
300			* restricted range, and <tt>toKey</tt> lies outside the
301			* bounds of the range
302	dl	1.1	*/
303	dl	1.3	NavigableMap<K,V> navigableHeadMap(K toKey);
304	dl	1.1
305			/**
306			* Returns a view of the portion of this map whose keys are
307	jsr166	1.8	* greater than or equal to <tt>fromKey</tt>. The returned map is
308			* backed by this map, so changes in the returned map are
309			* reflected in this map, and vice-versa. The returned map
310			* supports all optional map operations that this map supports.
311			*
312			* <p>The returned map will throw an <tt>IllegalArgumentException</tt>
313			* on an attempt to insert a key outside its range.
314			*
315			* @param fromKey low endpoint (inclusive) of the keys in the returned map
316	dl	1.1	* @return a view of the portion of this map whose keys are greater
317	jsr166	1.8	* than or equal to <tt>fromKey</tt>
318	dl	1.1	* @throws ClassCastException if <tt>fromKey</tt> is not compatible
319			* with this map's comparator (or, if the map has no comparator,
320	jsr166	1.8	* if <tt>fromKey</tt> does not implement {@link Comparable}).
321			* Implementations may, but are not required to, throw this
322			* exception if <tt>fromKey</tt> cannot be compared to keys
323			* currently in the map.
324			* @throws NullPointerException if <tt>fromKey</tt> is null
325			* and this map does not permit null keys
326			* @throws IllegalArgumentException if this map itself has a
327			* restricted range, and <tt>fromKey</tt> lies outside the
328			* bounds of the range
329	dl	1.1	*/
330	jsr166	1.8	NavigableMap<K,V> navigableTailMap(K fromKey);
331	dl	1.1	}