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 <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:	1.9
Committed:	Wed May 18 01:39:35 2005 UTC (18 years, 11 months ago) by jsr166
Branch:	MAIN
Changes since 1.8:	+2 -2 lines
Log Message:	keySet docs
#	Content
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	* 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	*
34	* <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	* <p>This interface is a member of the
47	* <a href="{@docRoot}/../guide/collections/index.html">
48	* Java Collections Framework</a>.
49	*
50	* @author Doug Lea
51	* @param <K> the type of keys maintained by this map
52	* @param <V> the type of mapped values
53	* @since 1.6
54	*/
55	public interface NavigableMap<K,V> extends SortedMap<K,V> {
56	/**
57	* 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	*
61	* @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	*/
69	Map.Entry<K,V> lowerEntry(K key);
70
71	/**
72	* Returns the greatest key strictly less than the given key, or
73	* <tt>null</tt> if there is no such key.
74	*
75	* @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	*/
83	K lowerKey(K key);
84
85	/**
86	* 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	*
90	* @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	*/
98	Map.Entry<K,V> floorEntry(K key);
99
100	/**
101	* Returns the greatest key less than or equal to the given key,
102	* or <tt>null</tt> if there is no such key.
103	*
104	* @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	*/
112	K floorKey(K key);
113
114	/**
115	* 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	*
119	* @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	*/
127	Map.Entry<K,V> ceilingEntry(K key);
128
129	/**
130	* Returns the least key greater than or equal to the given key,
131	* or <tt>null</tt> if there is no such key.
132	*
133	* @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	*/
141	K ceilingKey(K key);
142
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	* is no such key.
147	*
148	* @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	*/
156	Map.Entry<K,V> higherEntry(K key);
157
158	/**
159	* Returns the least key strictly greater than the given key, or
160	* <tt>null</tt> if there is no such key.
161	*
162	* @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	*/
170	K higherKey(K key);
171
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	*
176	* @return an entry with the least key,
177	* or <tt>null</tt> if this map is empty
178	*/
179	Map.Entry<K,V> firstEntry();
180
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	*
185	* @return an entry with the greatest key,
186	* or <tt>null</tt> if this map is empty
187	*/
188	Map.Entry<K,V> lastEntry();
189
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	*
194	* @return the removed first entry of this map,
195	* or <tt>null</tt> if this map is empty
196	*/
197	Map.Entry<K,V> pollFirstEntry();
198
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	*
203	* @return the removed last entry of this map,
204	* or <tt>null</tt> if this map is empty
205	*/
206	Map.Entry<K,V> pollLastEntry();
207
208	/**
209	* 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	* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
219	* operations. It does not support the <tt>add</tt> or <tt>addAll</tt>
220	* operations.
221	*
222	* @return a set view of the keys contained in this map, sorted in
223	* descending order
224	*/
225	Set<K> descendingKeySet();
226
227	/**
228	* 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	*
242	* @return a set view of the mappings contained in this map,
243	* sorted in descending key order
244	*/
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	* <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	*
256	* <p>The returned map will throw an <tt>IllegalArgumentException</tt>
257	* on an attempt to insert a key outside its range.
258	*
259	* @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	* @return a view of the portion of this map whose keys range from
262	* <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	*/
276	NavigableMap<K,V> navigableSubMap(K fromKey, K toKey);
277
278	/**
279	* 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	* @return a view of the portion of this map whose keys are strictly
290	* less than <tt>toKey</tt>
291	* @throws ClassCastException if <tt>toKey</tt> is not compatible
292	* with this map's comparator (or, if the map has no comparator,
293	* 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	*/
303	NavigableMap<K,V> navigableHeadMap(K toKey);
304
305	/**
306	* Returns a view of the portion of this map whose keys are
307	* 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	* @return a view of the portion of this map whose keys are greater
317	* than or equal to <tt>fromKey</tt>
318	* @throws ClassCastException if <tt>fromKey</tt> is not compatible
319	* with this map's comparator (or, if the map has no comparator,
320	* 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	*/
330	NavigableMap<K,V> navigableTailMap(K fromKey);
331	}