java/util/NavigableMap.java

/*
 * Written by Doug Lea and Josh Bloch with assistance from members of JCP
 * JSR-166 Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

package java.util;

/**
 * A {@link SortedMap} extended with navigation methods returning the
 * closest matches for given search targets. Methods
 * {@link #lowerEntry}, {@link #floorEntry}, {@link #ceilingEntry},
 * and {@link #higherEntry} return {@code Map.Entry} objects
 * associated with keys respectively less than, less than or equal,
 * greater than or equal, and greater than a given key, returning
 * {@code null} if there is no such key.  Similarly, methods
 * {@link #lowerKey}, {@link #floorKey}, {@link #ceilingKey}, and
 * {@link #higherKey} return only the associated keys. All of these
 * methods are designed for locating, not traversing entries.
 *
 * <p>A {@code NavigableMap} may be accessed and traversed in either
 * ascending or descending key order.  The {@link #descendingMap}
 * method returns a view of the map with the senses of all relational
 * and directional methods inverted. The performance of ascending
 * operations and views is likely to be faster than that of descending
 * ones.  Methods
 * {@link #subMap(Object, boolean, Object, boolean) subMap(K, boolean, K, boolean)},
 * {@link #headMap(Object, boolean) headMap(K, boolean)}, and
 * {@link #tailMap(Object, boolean) tailMap(K, boolean)}
 * differ from the like-named {@code SortedMap} methods in accepting
 * additional arguments describing whether lower and upper bounds are
 * inclusive versus exclusive.  Submaps of any {@code NavigableMap}
 * must implement the {@code NavigableMap} interface.
 *
 * <p>This interface additionally defines methods {@link #firstEntry},
 * {@link #pollFirstEntry}, {@link #lastEntry}, and
 * {@link #pollLastEntry} that return and/or remove the least and
 * greatest mappings, if any exist, else returning {@code null}.
 *
 * <p>Implementations of entry-returning methods are expected to
 * return {@code Map.Entry} pairs representing snapshots of mappings
 * at the time they were produced, and thus generally do <em>not</em>
 * support the optional {@code Entry.setValue} method. Note however
 * that it is possible to change mappings in the associated map using
 * method {@code put}.
 *
 * <p>Methods
 * {@link #subMap(Object, Object) subMap(K, K)},
 * {@link #headMap(Object) headMap(K)}, and
 * {@link #tailMap(Object) tailMap(K)}
 * are specified to return {@code SortedMap} to allow existing
 * implementations of {@code SortedMap} to be compatibly retrofitted to
 * implement {@code NavigableMap}, but extensions and implementations
 * of this interface are encouraged to override these methods to return
 * {@code NavigableMap}.  Similarly,
 * {@link #keySet()} can be overridden to return {@link NavigableSet}.
 *
 * <p>This interface is a member of the
 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
 * Java Collections Framework</a>.
 *
 * @author Doug Lea
 * @author Josh Bloch
 * @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 {@code null} if there is
     * no such key.
     *
     * @param key the key
     * @return an entry with the greatest key less than {@code key},
     *         or {@code null} 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
     * {@code null} if there is no such key.
     *
     * @param key the key
     * @return the greatest key less than {@code key},
     *         or {@code null} 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 {@code null} if there
     * is no such key.
     *
     * @param key the key
     * @return an entry with the greatest key less than or equal to
     *         {@code key}, or {@code null} 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 {@code null} if there is no such key.
     *
     * @param key the key
     * @return the greatest key less than or equal to {@code key},
     *         or {@code null} 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 {@code null} if
     * there is no such key.
     *
     * @param key the key
     * @return an entry with the least key greater than or equal to
     *         {@code key}, or {@code null} 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 {@code null} if there is no such key.
     *
     * @param key the key
     * @return the least key greater than or equal to {@code key},
     *         or {@code null} 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 {@code null} if there
     * is no such key.
     *
     * @param key the key
     * @return an entry with the least key greater than {@code key},
     *         or {@code null} 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
     * {@code null} if there is no such key.
     *
     * @param key the key
     * @return the least key greater than {@code key},
     *         or {@code null} 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 {@code null} if the map is empty.
     *
     * @return an entry with the least key,
     *         or {@code null} if this map is empty
     */
    Map.Entry<K,V> firstEntry();

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

    /**
     * Returns a reverse order view of the mappings contained in this map.
     * The descending map is backed by this map, so changes to the map are
     * reflected in the descending map, and vice-versa.  If either map is
     * modified while an iteration over a collection view of either map
     * is in progress (except through the iterator's own {@code remove}
     * operation), the results of the iteration are undefined.
     *
     * <p>The returned map has an ordering equivalent to
     * {@link Collections#reverseOrder(Comparator) Collections.reverseOrder}{@code (comparator())}.
     * The expression {@code m.descendingMap().descendingMap()} returns a
     * view of {@code m} essentially equivalent to {@code m}.
     *
     * @return a reverse order view of this map
     */
    NavigableMap<K,V> descendingMap();

    /**
     * Returns a {@link NavigableSet} view of the keys contained in this map.
     * The set's iterator returns the keys in ascending 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 {@code
     * remove} operation), the results of the iteration are undefined.  The
     * set supports element removal, which removes the corresponding mapping
     * from the map, via the {@code Iterator.remove}, {@code Set.remove},
     * {@code removeAll}, {@code retainAll}, and {@code clear} operations.
     * It does not support the {@code add} or {@code addAll} operations.
     *
     * @return a navigable set view of the keys in this map
     */
    NavigableSet<K> navigableKeySet();

    /**
     * Returns a reverse order {@link NavigableSet} 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 {@code
     * remove} operation), the results of the iteration are undefined.  The
     * set supports element removal, which removes the corresponding mapping
     * from the map, via the {@code Iterator.remove}, {@code Set.remove},
     * {@code removeAll}, {@code retainAll}, and {@code clear} operations.
     * It does not support the {@code add} or {@code addAll} operations.
     *
     * @return a reverse order navigable set view of the keys in this map
     */
    NavigableSet<K> descendingKeySet();

    /**
     * Returns a view of the portion of this map whose keys range from
     * {@code fromKey} to {@code toKey}.  If {@code fromKey} and
     * {@code toKey} are equal, the returned map is empty unless
     * {@code fromInclusive} and {@code toInclusive} are both true.  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 {@code IllegalArgumentException}
     * on an attempt to insert a key outside of its range, or to construct a
     * submap either of whose endpoints lie outside its range.
     *
     * @param fromKey low endpoint of the keys in the returned map
     * @param fromInclusive {@code true} if the low endpoint
     *        is to be included in the returned view
     * @param toKey high endpoint of the keys in the returned map
     * @param toInclusive {@code true} if the high endpoint
     *        is to be included in the returned view
     * @return a view of the portion of this map whose keys range from
     *         {@code fromKey} to {@code toKey}
     * @throws ClassCastException if {@code fromKey} and {@code toKey}
     *         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 {@code fromKey} or {@code toKey}
     *         cannot be compared to keys currently in the map.
     * @throws NullPointerException if {@code fromKey} or {@code toKey}
     *         is null and this map does not permit null keys
     * @throws IllegalArgumentException if {@code fromKey} is greater than
     *         {@code toKey}; or if this map itself has a restricted
     *         range, and {@code fromKey} or {@code toKey} lies
     *         outside the bounds of the range
     */
    NavigableMap<K,V> subMap(K fromKey, boolean fromInclusive,
                             K toKey,   boolean toInclusive);

    /**
     * Returns a view of the portion of this map whose keys are less than (or
     * equal to, if {@code inclusive} is true) {@code toKey}.  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 {@code IllegalArgumentException}
     * on an attempt to insert a key outside its range.
     *
     * @param toKey high endpoint of the keys in the returned map
     * @param inclusive {@code true} if the high endpoint
     *        is to be included in the returned view
     * @return a view of the portion of this map whose keys are less than
     *         (or equal to, if {@code inclusive} is true) {@code toKey}
     * @throws ClassCastException if {@code toKey} is not compatible
     *         with this map's comparator (or, if the map has no comparator,
     *         if {@code toKey} does not implement {@link Comparable}).
     *         Implementations may, but are not required to, throw this
     *         exception if {@code toKey} cannot be compared to keys
     *         currently in the map.
     * @throws NullPointerException if {@code toKey} is null
     *         and this map does not permit null keys
     * @throws IllegalArgumentException if this map itself has a
     *         restricted range, and {@code toKey} lies outside the
     *         bounds of the range
     */
    NavigableMap<K,V> headMap(K toKey, boolean inclusive);

    /**
     * Returns a view of the portion of this map whose keys are greater than (or
     * equal to, if {@code inclusive} is true) {@code fromKey}.  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 {@code IllegalArgumentException}
     * on an attempt to insert a key outside its range.
     *
     * @param fromKey low endpoint of the keys in the returned map
     * @param inclusive {@code true} if the low endpoint
     *        is to be included in the returned view
     * @return a view of the portion of this map whose keys are greater than
     *         (or equal to, if {@code inclusive} is true) {@code fromKey}
     * @throws ClassCastException if {@code fromKey} is not compatible
     *         with this map's comparator (or, if the map has no comparator,
     *         if {@code fromKey} does not implement {@link Comparable}).
     *         Implementations may, but are not required to, throw this
     *         exception if {@code fromKey} cannot be compared to keys
     *         currently in the map.
     * @throws NullPointerException if {@code fromKey} is null
     *         and this map does not permit null keys
     * @throws IllegalArgumentException if this map itself has a
     *         restricted range, and {@code fromKey} lies outside the
     *         bounds of the range
     */
    NavigableMap<K,V> tailMap(K fromKey, boolean inclusive);

    /**
     * {@inheritDoc}
     *
     * <p>Equivalent to {@code subMap(fromKey, true, toKey, false)}.
     *
     * @throws ClassCastException       {@inheritDoc}
     * @throws NullPointerException     {@inheritDoc}
     * @throws IllegalArgumentException {@inheritDoc}
     */
    SortedMap<K,V> subMap(K fromKey, K toKey);

    /**
     * {@inheritDoc}
     *
     * <p>Equivalent to {@code headMap(toKey, false)}.
     *
     * @throws ClassCastException       {@inheritDoc}
     * @throws NullPointerException     {@inheritDoc}
     * @throws IllegalArgumentException {@inheritDoc}
     */
    SortedMap<K,V> headMap(K toKey);

    /**
     * {@inheritDoc}
     *
     * <p>Equivalent to {@code tailMap(fromKey, true)}.
     *
     * @throws ClassCastException       {@inheritDoc}
     * @throws NullPointerException     {@inheritDoc}
     * @throws IllegalArgumentException {@inheritDoc}
     */
    SortedMap<K,V> tailMap(K fromKey);
}
Revision:	1.1
Committed:	Sat Mar 26 06:22:49 2016 UTC (8 years, 1 month ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Log Message:	fork jdk8 maintenance branch for source and jtreg tests
#	User	Rev	Content
1	jsr166	1.1	/*
2			* Written by Doug Lea and Josh Bloch with assistance from members of JCP
3			* JSR-166 Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/publicdomain/zero/1.0/
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			* {@link #lowerEntry}, {@link #floorEntry}, {@link #ceilingEntry},
13			* and {@link #higherEntry} return {@code Map.Entry} 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			* {@code null} if there is no such key. Similarly, methods
17			* {@link #lowerKey}, {@link #floorKey}, {@link #ceilingKey}, and
18			* {@link #higherKey} return only the associated keys. All of these
19			* methods are designed for locating, not traversing entries.
20			*
21			* <p>A {@code NavigableMap} may be accessed and traversed in either
22			* ascending or descending key order. The {@link #descendingMap}
23			* method returns a view of the map with the senses of all relational
24			* and directional methods inverted. The performance of ascending
25			* operations and views is likely to be faster than that of descending
26			* ones. Methods
27			* {@link #subMap(Object, boolean, Object, boolean) subMap(K, boolean, K, boolean)},
28			* {@link #headMap(Object, boolean) headMap(K, boolean)}, and
29			* {@link #tailMap(Object, boolean) tailMap(K, boolean)}
30			* differ from the like-named {@code SortedMap} methods in accepting
31			* additional arguments describing whether lower and upper bounds are
32			* inclusive versus exclusive. Submaps of any {@code NavigableMap}
33			* must implement the {@code NavigableMap} interface.
34			*
35			* <p>This interface additionally defines methods {@link #firstEntry},
36			* {@link #pollFirstEntry}, {@link #lastEntry}, and
37			* {@link #pollLastEntry} that return and/or remove the least and
38			* greatest mappings, if any exist, else returning {@code null}.
39			*
40			* <p>Implementations of entry-returning methods are expected to
41			* return {@code Map.Entry} pairs representing snapshots of mappings
42			* at the time they were produced, and thus generally do <em>not</em>
43			* support the optional {@code Entry.setValue} method. Note however
44			* that it is possible to change mappings in the associated map using
45			* method {@code put}.
46			*
47			* <p>Methods
48			* {@link #subMap(Object, Object) subMap(K, K)},
49			* {@link #headMap(Object) headMap(K)}, and
50			* {@link #tailMap(Object) tailMap(K)}
51			* are specified to return {@code SortedMap} to allow existing
52			* implementations of {@code SortedMap} to be compatibly retrofitted to
53			* implement {@code NavigableMap}, but extensions and implementations
54			* of this interface are encouraged to override these methods to return
55			* {@code NavigableMap}. Similarly,
56			* {@link #keySet()} can be overridden to return {@link NavigableSet}.
57			*
58			* <p>This interface is a member of the
59			* <a href="{@docRoot}/../technotes/guides/collections/index.html">
60			* Java Collections Framework</a>.
61			*
62			* @author Doug Lea
63			* @author Josh Bloch
64			* @param <K> the type of keys maintained by this map
65			* @param <V> the type of mapped values
66			* @since 1.6
67			*/
68			public interface NavigableMap<K,V> extends SortedMap<K,V> {
69			/**
70			* Returns a key-value mapping associated with the greatest key
71			* strictly less than the given key, or {@code null} if there is
72			* no such key.
73			*
74			* @param key the key
75			* @return an entry with the greatest key less than {@code key},
76			* or {@code null} if there is no such key
77			* @throws ClassCastException if the specified key cannot be compared
78			* with the keys currently in the map
79			* @throws NullPointerException if the specified key is null
80			* and this map does not permit null keys
81			*/
82			Map.Entry<K,V> lowerEntry(K key);
83
84			/**
85			* Returns the greatest key strictly less than the given key, or
86			* {@code null} if there is no such key.
87			*
88			* @param key the key
89			* @return the greatest key less than {@code key},
90			* or {@code null} if there is no such key
91			* @throws ClassCastException if the specified key cannot be compared
92			* with the keys currently in the map
93			* @throws NullPointerException if the specified key is null
94			* and this map does not permit null keys
95			*/
96			K lowerKey(K key);
97
98			/**
99			* Returns a key-value mapping associated with the greatest key
100			* less than or equal to the given key, or {@code null} if there
101			* is no such key.
102			*
103			* @param key the key
104			* @return an entry with the greatest key less than or equal to
105			* {@code key}, or {@code null} if there is no such key
106			* @throws ClassCastException if the specified key cannot be compared
107			* with the keys currently in the map
108			* @throws NullPointerException if the specified key is null
109			* and this map does not permit null keys
110			*/
111			Map.Entry<K,V> floorEntry(K key);
112
113			/**
114			* Returns the greatest key less than or equal to the given key,
115			* or {@code null} if there is no such key.
116			*
117			* @param key the key
118			* @return the greatest key less than or equal to {@code key},
119			* or {@code null} if there is no such key
120			* @throws ClassCastException if the specified key cannot be compared
121			* with the keys currently in the map
122			* @throws NullPointerException if the specified key is null
123			* and this map does not permit null keys
124			*/
125			K floorKey(K key);
126
127			/**
128			* Returns a key-value mapping associated with the least key
129			* greater than or equal to the given key, or {@code null} if
130			* there is no such key.
131			*
132			* @param key the key
133			* @return an entry with the least key greater than or equal to
134			* {@code key}, or {@code null} if there is no such key
135			* @throws ClassCastException if the specified key cannot be compared
136			* with the keys currently in the map
137			* @throws NullPointerException if the specified key is null
138			* and this map does not permit null keys
139			*/
140			Map.Entry<K,V> ceilingEntry(K key);
141
142			/**
143			* Returns the least key greater than or equal to the given key,
144			* or {@code null} if there is no such key.
145			*
146			* @param key the key
147			* @return the least key greater than or equal to {@code key},
148			* or {@code null} if there is no such key
149			* @throws ClassCastException if the specified key cannot be compared
150			* with the keys currently in the map
151			* @throws NullPointerException if the specified key is null
152			* and this map does not permit null keys
153			*/
154			K ceilingKey(K key);
155
156			/**
157			* Returns a key-value mapping associated with the least key
158			* strictly greater than the given key, or {@code null} if there
159			* is no such key.
160			*
161			* @param key the key
162			* @return an entry with the least key greater than {@code key},
163			* or {@code null} if there is no such key
164			* @throws ClassCastException if the specified key cannot be compared
165			* with the keys currently in the map
166			* @throws NullPointerException if the specified key is null
167			* and this map does not permit null keys
168			*/
169			Map.Entry<K,V> higherEntry(K key);
170
171			/**
172			* Returns the least key strictly greater than the given key, or
173			* {@code null} if there is no such key.
174			*
175			* @param key the key
176			* @return the least key greater than {@code key},
177			* or {@code null} if there is no such key
178			* @throws ClassCastException if the specified key cannot be compared
179			* with the keys currently in the map
180			* @throws NullPointerException if the specified key is null
181			* and this map does not permit null keys
182			*/
183			K higherKey(K key);
184
185			/**
186			* Returns a key-value mapping associated with the least
187			* key in this map, or {@code null} if the map is empty.
188			*
189			* @return an entry with the least key,
190			* or {@code null} if this map is empty
191			*/
192			Map.Entry<K,V> firstEntry();
193
194			/**
195			* Returns a key-value mapping associated with the greatest
196			* key in this map, or {@code null} if the map is empty.
197			*
198			* @return an entry with the greatest key,
199			* or {@code null} if this map is empty
200			*/
201			Map.Entry<K,V> lastEntry();
202
203			/**
204			* Removes and returns a key-value mapping associated with
205			* the least key in this map, or {@code null} if the map is empty.
206			*
207			* @return the removed first entry of this map,
208			* or {@code null} if this map is empty
209			*/
210			Map.Entry<K,V> pollFirstEntry();
211
212			/**
213			* Removes and returns a key-value mapping associated with
214			* the greatest key in this map, or {@code null} if the map is empty.
215			*
216			* @return the removed last entry of this map,
217			* or {@code null} if this map is empty
218			*/
219			Map.Entry<K,V> pollLastEntry();
220
221			/**
222			* Returns a reverse order view of the mappings contained in this map.
223			* The descending map is backed by this map, so changes to the map are
224			* reflected in the descending map, and vice-versa. If either map is
225			* modified while an iteration over a collection view of either map
226			* is in progress (except through the iterator's own {@code remove}
227			* operation), the results of the iteration are undefined.
228			*
229			* <p>The returned map has an ordering equivalent to
230			* {@link Collections#reverseOrder(Comparator) Collections.reverseOrder}{@code (comparator())}.
231			* The expression {@code m.descendingMap().descendingMap()} returns a
232			* view of {@code m} essentially equivalent to {@code m}.
233			*
234			* @return a reverse order view of this map
235			*/
236			NavigableMap<K,V> descendingMap();
237
238			/**
239			* Returns a {@link NavigableSet} view of the keys contained in this map.
240			* The set's iterator returns the keys in ascending order.
241			* The set is backed by the map, so changes to the map are reflected in
242			* the set, and vice-versa. If the map is modified while an iteration
243			* over the set is in progress (except through the iterator's own {@code
244			* remove} operation), the results of the iteration are undefined. The
245			* set supports element removal, which removes the corresponding mapping
246			* from the map, via the {@code Iterator.remove}, {@code Set.remove},
247			* {@code removeAll}, {@code retainAll}, and {@code clear} operations.
248			* It does not support the {@code add} or {@code addAll} operations.
249			*
250			* @return a navigable set view of the keys in this map
251			*/
252			NavigableSet<K> navigableKeySet();
253
254			/**
255			* Returns a reverse order {@link NavigableSet} view of the keys contained in this map.
256			* The set's iterator returns the keys in descending order.
257			* The set is backed by the map, so changes to the map are reflected in
258			* the set, and vice-versa. If the map is modified while an iteration
259			* over the set is in progress (except through the iterator's own {@code
260			* remove} operation), the results of the iteration are undefined. The
261			* set supports element removal, which removes the corresponding mapping
262			* from the map, via the {@code Iterator.remove}, {@code Set.remove},
263			* {@code removeAll}, {@code retainAll}, and {@code clear} operations.
264			* It does not support the {@code add} or {@code addAll} operations.
265			*
266			* @return a reverse order navigable set view of the keys in this map
267			*/
268			NavigableSet<K> descendingKeySet();
269
270			/**
271			* Returns a view of the portion of this map whose keys range from
272			* {@code fromKey} to {@code toKey}. If {@code fromKey} and
273			* {@code toKey} are equal, the returned map is empty unless
274			* {@code fromInclusive} and {@code toInclusive} are both true. The
275			* returned map is backed by this map, so changes in the returned map are
276			* reflected in this map, and vice-versa. The returned map supports all
277			* optional map operations that this map supports.
278			*
279			* <p>The returned map will throw an {@code IllegalArgumentException}
280			* on an attempt to insert a key outside of its range, or to construct a
281			* submap either of whose endpoints lie outside its range.
282			*
283			* @param fromKey low endpoint of the keys in the returned map
284			* @param fromInclusive {@code true} if the low endpoint
285			* is to be included in the returned view
286			* @param toKey high endpoint of the keys in the returned map
287			* @param toInclusive {@code true} if the high endpoint
288			* is to be included in the returned view
289			* @return a view of the portion of this map whose keys range from
290			* {@code fromKey} to {@code toKey}
291			* @throws ClassCastException if {@code fromKey} and {@code toKey}
292			* cannot be compared to one another using this map's comparator
293			* (or, if the map has no comparator, using natural ordering).
294			* Implementations may, but are not required to, throw this
295			* exception if {@code fromKey} or {@code toKey}
296			* cannot be compared to keys currently in the map.
297			* @throws NullPointerException if {@code fromKey} or {@code toKey}
298			* is null and this map does not permit null keys
299			* @throws IllegalArgumentException if {@code fromKey} is greater than
300			* {@code toKey}; or if this map itself has a restricted
301			* range, and {@code fromKey} or {@code toKey} lies
302			* outside the bounds of the range
303			*/
304			NavigableMap<K,V> subMap(K fromKey, boolean fromInclusive,
305			K toKey, boolean toInclusive);
306
307			/**
308			* Returns a view of the portion of this map whose keys are less than (or
309			* equal to, if {@code inclusive} is true) {@code toKey}. The returned
310			* map is backed by this map, so changes in the returned map are reflected
311			* in this map, and vice-versa. The returned map supports all optional
312			* map operations that this map supports.
313			*
314			* <p>The returned map will throw an {@code IllegalArgumentException}
315			* on an attempt to insert a key outside its range.
316			*
317			* @param toKey high endpoint of the keys in the returned map
318			* @param inclusive {@code true} if the high endpoint
319			* is to be included in the returned view
320			* @return a view of the portion of this map whose keys are less than
321			* (or equal to, if {@code inclusive} is true) {@code toKey}
322			* @throws ClassCastException if {@code toKey} is not compatible
323			* with this map's comparator (or, if the map has no comparator,
324			* if {@code toKey} does not implement {@link Comparable}).
325			* Implementations may, but are not required to, throw this
326			* exception if {@code toKey} cannot be compared to keys
327			* currently in the map.
328			* @throws NullPointerException if {@code toKey} is null
329			* and this map does not permit null keys
330			* @throws IllegalArgumentException if this map itself has a
331			* restricted range, and {@code toKey} lies outside the
332			* bounds of the range
333			*/
334			NavigableMap<K,V> headMap(K toKey, boolean inclusive);
335
336			/**
337			* Returns a view of the portion of this map whose keys are greater than (or
338			* equal to, if {@code inclusive} is true) {@code fromKey}. The returned
339			* map is backed by this map, so changes in the returned map are reflected
340			* in this map, and vice-versa. The returned map supports all optional
341			* map operations that this map supports.
342			*
343			* <p>The returned map will throw an {@code IllegalArgumentException}
344			* on an attempt to insert a key outside its range.
345			*
346			* @param fromKey low endpoint of the keys in the returned map
347			* @param inclusive {@code true} if the low endpoint
348			* is to be included in the returned view
349			* @return a view of the portion of this map whose keys are greater than
350			* (or equal to, if {@code inclusive} is true) {@code fromKey}
351			* @throws ClassCastException if {@code fromKey} is not compatible
352			* with this map's comparator (or, if the map has no comparator,
353			* if {@code fromKey} does not implement {@link Comparable}).
354			* Implementations may, but are not required to, throw this
355			* exception if {@code fromKey} cannot be compared to keys
356			* currently in the map.
357			* @throws NullPointerException if {@code fromKey} is null
358			* and this map does not permit null keys
359			* @throws IllegalArgumentException if this map itself has a
360			* restricted range, and {@code fromKey} lies outside the
361			* bounds of the range
362			*/
363			NavigableMap<K,V> tailMap(K fromKey, boolean inclusive);
364
365			/**
366			* {@inheritDoc}
367			*
368			* <p>Equivalent to {@code subMap(fromKey, true, toKey, false)}.
369			*
370			* @throws ClassCastException {@inheritDoc}
371			* @throws NullPointerException {@inheritDoc}
372			* @throws IllegalArgumentException {@inheritDoc}
373			*/
374			SortedMap<K,V> subMap(K fromKey, K toKey);
375
376			/**
377			* {@inheritDoc}
378			*
379			* <p>Equivalent to {@code headMap(toKey, false)}.
380			*
381			* @throws ClassCastException {@inheritDoc}
382			* @throws NullPointerException {@inheritDoc}
383			* @throws IllegalArgumentException {@inheritDoc}
384			*/
385			SortedMap<K,V> headMap(K toKey);
386
387			/**
388			* {@inheritDoc}
389			*
390			* <p>Equivalent to {@code tailMap(fromKey, true)}.
391			*
392			* @throws ClassCastException {@inheritDoc}
393			* @throws NullPointerException {@inheritDoc}
394			* @throws IllegalArgumentException {@inheritDoc}
395			*/
396			SortedMap<K,V> tailMap(K fromKey);
397			}