java/util/NavigableSet.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/licenses/publicdomain
 */

package java.util;

/**
 * A {@link SortedSet} extended with navigation methods reporting
 * closest matches for given search targets. Methods <tt>lower},
 * {@code floor}, {@code ceiling}, and {@code higher} return elements
 * respectively less than, less than or equal, greater than or equal,
 * and greater than a given element, returning {@code null} if there
 * is no such element.  A {@code NavigableSet} may be accessed and
 * traversed in either ascending or descending order.  The {@code
 * descendingSet} method returns a view of the set 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.  This interface additionally defines methods
 * {@code pollFirst} and {@code pollLast} that return and remove the
 * lowest and highest element, if one exists, else returning {@code
 * null}.  Methods {@code subSet}, {@code headSet},
 * and {@code tailSet} differ from the like-named {@code
 * SortedSet} methods in accepting additional arguments describing
 * whether lower and upper bounds are inclusive versus exclusive.
 * Subsets of any {@code NavigableSet} must implement the {@code
 * NavigableSet} interface.
 *
 * <p> The return values of navigation methods may be ambiguous in
 * implementations that permit {@code null} elements. However, even
 * in this case the result can be disambiguated by checking
 * {@code contains(null)}. To avoid such issues, implementations of
 * this interface are encouraged to <em>not</em> permit insertion of
 * {@code null} elements. (Note that sorted sets of {@link
 * Comparable} elements intrinsically do not permit {@code null}.)
 *
 * <p>This interface is a member of the
 * <a href="{@docRoot}/../guide/collections/index.html">
 * Java Collections Framework</a>.
 *
 * @author Doug Lea
 * @author Josh Bloch
 * @param <E> the type of elements maintained by this set
 * @since 1.6
 */
public interface NavigableSet<E> extends SortedSet<E> {
    /**
     * Returns the greatest element in this set strictly less than the
     * given element, or {@code null} if there is no such element.
     *
     * @param e the value to match
     * @return the greatest element less than {@code e},
     *         or {@code null} if there is no such element
     * @throws ClassCastException if the specified element cannot be
     *         compared with the elements currently in the set
     * @throws NullPointerException if the specified element is null
     *         and this set does not permit null elements
     */
    E lower(E e);

    /**
     * Returns the greatest element in this set less than or equal to
     * the given element, or {@code null} if there is no such element.
     *
     * @param e the value to match
     * @return the greatest element less than or equal to {@code e},
     *         or {@code null} if there is no such element
     * @throws ClassCastException if the specified element cannot be
     *         compared with the elements currently in the set
     * @throws NullPointerException if the specified element is null
     *         and this set does not permit null elements
     */
    E floor(E e);

    /**
     * Returns the least element in this set greater than or equal to
     * the given element, or {@code null} if there is no such element.
     *
     * @param e the value to match
     * @return the least element greater than or equal to {@code e},
     *         or {@code null} if there is no such element
     * @throws ClassCastException if the specified element cannot be
     *         compared with the elements currently in the set
     * @throws NullPointerException if the specified element is null
     *         and this set does not permit null elements
     */
    E ceiling(E e);

    /**
     * Returns the least element in this set strictly greater than the
     * given element, or {@code null} if there is no such element.
     *
     * @param e the value to match
     * @return the least element greater than {@code e},
     *         or {@code null} if there is no such element
     * @throws ClassCastException if the specified element cannot be
     *         compared with the elements currently in the set
     * @throws NullPointerException if the specified element is null
     *         and this set does not permit null elements
     */
    E higher(E e);

    /**
     * Retrieves and removes the first (lowest) element,
     * or returns {@code null} if this set is empty.
     *
     * @return the first element, or {@code null} if this set is empty
     */
    E pollFirst();

    /**
     * Retrieves and removes the last (highest) element,
     * or returns {@code null} if this set is empty.
     *
     * @return the last element, or {@code null} if this set is empty
     */
    E pollLast();

    /**
     * Returns an iterator over the elements in this set, in ascending order.
     *
     * @return an iterator over the elements in this set, in ascending order
     */
    Iterator<E> iterator();

    /**
     * Returns a {@link NavigableSet} view of the elements contained in this
     * set in descending order.  The descending set is backed by this set, so
     * changes to the set are reflected in the descending set, and vice-versa.
     * If either set is modified while an iteration over the other set is in
     * in progress (except through the iterator's own {@code remove} operation),
     * the results of the iteration are undefined.
     *
     * @return a navigable set view of the mappings contained in this set,
     *     sorted in descending order
     */
    NavigableSet<E> descendingSet();

    /**
     * Returns an iterator over the elements in this set, in descending order.
     * Equivalent in effect to <tt>descendingSet().iterator()</tt>.
     *
     * @return an iterator over the elements in this set, in descending order
     */
    Iterator<E> descendingIterator();

    /**
     * Returns a view of the portion of this set whose elements range from
     * {@code fromElement} to {@code toElement}.  If {@code fromElement} and
     * {@code toElement} are equal, the returned set is empty unless {@code
     * fromExclusive} and {@code toExclusive} are both true.  The returned set
     * is backed by this set, so changes in the returned set are reflected in
     * this set, and vice-versa.  The returned set supports all optional set
     * operations that this set supports.
     *
     * <p>The returned set will throw an {@code IllegalArgumentException}
     * on an attempt to insert an element outside its range.
     *
     * @param fromElement low endpoint of the returned set
     * @param fromInclusive true if the low endpoint ({@code fromElement}) is
     *        to be included in the returned view
     * @param toElement high endpoint of the returned set
     * @param toInclusive true if the high endpoint ({@code toElement}) is
     *        to be included in the returned view
     * @return a view of the portion of this set whose elements range from
     *         {@code fromElement}, inclusive, to {@code toElement}, exclusive
     * @throws ClassCastException if {@code fromElement} and
     *         {@code toElement} cannot be compared to one another using this
     *         set's comparator (or, if the set has no comparator, using
     *         natural ordering).  Implementations may, but are not required
     *         to, throw this exception if {@code fromElement} or
     *         {@code toElement} cannot be compared to elements currently in
     *         the set.
     * @throws NullPointerException if {@code fromElement} or
     *         {@code toElement} is null and this set does
     *         not permit null elements
     * @throws IllegalArgumentException if {@code fromElement} is
     *         greater than {@code toElement}; or if this set itself
     *         has a restricted range, and {@code fromElement} or
     *         {@code toElement} lies outside the bounds of the range.
     */
    NavigableSet<E> subSet(E fromElement, boolean fromInclusive,
                           E toElement,   boolean toInclusive);

    /**
     * Returns a view of the portion of this set whose elements are less than
     * (or equal to, if {@code inclusive} is true) {@code toElement}.  The
     * returned set is backed by this set, so changes in the returned set are
     * reflected in this set, and vice-versa.  The returned set supports all
     * optional set operations that this set supports.
     *
     * <p>The returned set will throw an {@code IllegalArgumentException}
     * on an attempt to insert an element outside its range.
     *
     * @param toElement high endpoint of the returned set
     * @param inclusive true if the high endpoint ({@code toElement}) is
     *        to be included in the returned view
     * @return a view of the portion of this set whose elements are less than
     *         (or equal to, if {@code inclusive} is true) {@code toElement}
     * @throws ClassCastException if {@code toElement} is not compatible
     *         with this set's comparator (or, if the set has no comparator,
     *         if {@code toElement} does not implement {@link Comparable}).
     *         Implementations may, but are not required to, throw this
     *         exception if {@code toElement} cannot be compared to elements
     *         currently in the set.
     * @throws NullPointerException if {@code toElement} is null and
     *         this set does not permit null elements
     * @throws IllegalArgumentException if this set itself has a
     *         restricted range, and {@code toElement} lies outside the
     *         bounds of the range
     */
    NavigableSet<E> headSet(E toElement, boolean inclusive);

    /**
     * Returns a view of the portion of this set whose elements are greater
     * than (or equal to, if {@code inclusive} is true) {@code fromElement}.
     * The returned set is backed by this set, so changes in the returned set
     * are reflected in this set, and vice-versa.  The returned set supports
     * all optional set operations that this set supports.
     *
     * <p>The returned set will throw an {@code IllegalArgumentException}
     * on an attempt to insert an element outside its range.
     *
     * @param fromElement low endpoint of the returned set
     * @param inclusive true if the low endpoint ({@code fromElement}) is
     *        to be included in the returned view
     * @return a view of the portion of this set whose elements are greater
     *         than or equal to {@code fromElement}
     * @throws ClassCastException if {@code fromElement} is not compatible
     *         with this set's comparator (or, if the set has no comparator,
     *         if {@code fromElement} does not implement {@link Comparable}).
     *         Implementations may, but are not required to, throw this
     *         exception if {@code fromElement} cannot be compared to elements
     *         currently in the set.
     * @throws NullPointerException if {@code fromElement} is null
     *         and this set does not permit null elements
     * @throws IllegalArgumentException if this set itself has a
     *         restricted range, and {@code fromElement} lies outside the
     *         bounds of the range
     */
    NavigableSet<E> tailSet(E fromElement, boolean inclusive);
}
Revision:	1.17
Committed:	Thu Apr 20 21:55:42 2006 UTC (18 years, 1 month ago) by jsr166
Branch:	MAIN
Changes since 1.16:	+4 -4 lines
Log Message:	the the
#	Content
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/licenses/publicdomain
5	*/
6
7	package java.util;
8
9	/**
10	* A {@link SortedSet} extended with navigation methods reporting
11	* closest matches for given search targets. Methods <tt>lower},
12	* {@code floor}, {@code ceiling}, and {@code higher} return elements
13	* respectively less than, less than or equal, greater than or equal,
14	* and greater than a given element, returning {@code null} if there
15	* is no such element. A {@code NavigableSet} may be accessed and
16	* traversed in either ascending or descending order. The {@code
17	* descendingSet} method returns a view of the set with the senses of
18	* all relational and directional methods inverted. The performance of
19	* ascending operations and views is likely to be faster than that of
20	* descending ones. This interface additionally defines methods
21	* {@code pollFirst} and {@code pollLast} that return and remove the
22	* lowest and highest element, if one exists, else returning {@code
23	* null}. Methods {@code subSet}, {@code headSet},
24	* and {@code tailSet} differ from the like-named {@code
25	* SortedSet} methods in accepting additional arguments describing
26	* whether lower and upper bounds are inclusive versus exclusive.
27	* Subsets of any {@code NavigableSet} must implement the {@code
28	* NavigableSet} interface.
29	*
30	* <p> The return values of navigation methods may be ambiguous in
31	* implementations that permit {@code null} elements. However, even
32	* in this case the result can be disambiguated by checking
33	* {@code contains(null)}. To avoid such issues, implementations of
34	* this interface are encouraged to <em>not</em> permit insertion of
35	* {@code null} elements. (Note that sorted sets of {@link
36	* Comparable} elements intrinsically do not permit {@code null}.)
37	*
38	* <p>This interface is a member of the
39	* <a href="{@docRoot}/../guide/collections/index.html">
40	* Java Collections Framework</a>.
41	*
42	* @author Doug Lea
43	* @author Josh Bloch
44	* @param <E> the type of elements maintained by this set
45	* @since 1.6
46	*/
47	public interface NavigableSet<E> extends SortedSet<E> {
48	/**
49	* Returns the greatest element in this set strictly less than the
50	* given element, or {@code null} if there is no such element.
51	*
52	* @param e the value to match
53	* @return the greatest element less than {@code e},
54	* or {@code null} if there is no such element
55	* @throws ClassCastException if the specified element cannot be
56	* compared with the elements currently in the set
57	* @throws NullPointerException if the specified element is null
58	* and this set does not permit null elements
59	*/
60	E lower(E e);
61
62	/**
63	* Returns the greatest element in this set less than or equal to
64	* the given element, or {@code null} if there is no such element.
65	*
66	* @param e the value to match
67	* @return the greatest element less than or equal to {@code e},
68	* or {@code null} if there is no such element
69	* @throws ClassCastException if the specified element cannot be
70	* compared with the elements currently in the set
71	* @throws NullPointerException if the specified element is null
72	* and this set does not permit null elements
73	*/
74	E floor(E e);
75
76	/**
77	* Returns the least element in this set greater than or equal to
78	* the given element, or {@code null} if there is no such element.
79	*
80	* @param e the value to match
81	* @return the least element greater than or equal to {@code e},
82	* or {@code null} if there is no such element
83	* @throws ClassCastException if the specified element cannot be
84	* compared with the elements currently in the set
85	* @throws NullPointerException if the specified element is null
86	* and this set does not permit null elements
87	*/
88	E ceiling(E e);
89
90	/**
91	* Returns the least element in this set strictly greater than the
92	* given element, or {@code null} if there is no such element.
93	*
94	* @param e the value to match
95	* @return the least element greater than {@code e},
96	* or {@code null} if there is no such element
97	* @throws ClassCastException if the specified element cannot be
98	* compared with the elements currently in the set
99	* @throws NullPointerException if the specified element is null
100	* and this set does not permit null elements
101	*/
102	E higher(E e);
103
104	/**
105	* Retrieves and removes the first (lowest) element,
106	* or returns {@code null} if this set is empty.
107	*
108	* @return the first element, or {@code null} if this set is empty
109	*/
110	E pollFirst();
111
112	/**
113	* Retrieves and removes the last (highest) element,
114	* or returns {@code null} if this set is empty.
115	*
116	* @return the last element, or {@code null} if this set is empty
117	*/
118	E pollLast();
119
120	/**
121	* Returns an iterator over the elements in this set, in ascending order.
122	*
123	* @return an iterator over the elements in this set, in ascending order
124	*/
125	Iterator<E> iterator();
126
127	/**
128	* Returns a {@link NavigableSet} view of the elements contained in this
129	* set in descending order. The descending set is backed by this set, so
130	* changes to the set are reflected in the descending set, and vice-versa.
131	* If either set is modified while an iteration over the other set is in
132	* in progress (except through the iterator's own {@code remove} operation),
133	* the results of the iteration are undefined.
134	*
135	* @return a navigable set view of the mappings contained in this set,
136	* sorted in descending order
137	*/
138	NavigableSet<E> descendingSet();
139
140	/**
141	* Returns an iterator over the elements in this set, in descending order.
142	* Equivalent in effect to <tt>descendingSet().iterator()</tt>.
143	*
144	* @return an iterator over the elements in this set, in descending order
145	*/
146	Iterator<E> descendingIterator();
147
148	/**
149	* Returns a view of the portion of this set whose elements range from
150	* {@code fromElement} to {@code toElement}. If {@code fromElement} and
151	* {@code toElement} are equal, the returned set is empty unless {@code
152	* fromExclusive} and {@code toExclusive} are both true. The returned set
153	* is backed by this set, so changes in the returned set are reflected in
154	* this set, and vice-versa. The returned set supports all optional set
155	* operations that this set supports.
156	*
157	* <p>The returned set will throw an {@code IllegalArgumentException}
158	* on an attempt to insert an element outside its range.
159	*
160	* @param fromElement low endpoint of the returned set
161	* @param fromInclusive true if the low endpoint ({@code fromElement}) is
162	* to be included in the returned view
163	* @param toElement high endpoint of the returned set
164	* @param toInclusive true if the high endpoint ({@code toElement}) is
165	* to be included in the returned view
166	* @return a view of the portion of this set whose elements range from
167	* {@code fromElement}, inclusive, to {@code toElement}, exclusive
168	* @throws ClassCastException if {@code fromElement} and
169	* {@code toElement} cannot be compared to one another using this
170	* set's comparator (or, if the set has no comparator, using
171	* natural ordering). Implementations may, but are not required
172	* to, throw this exception if {@code fromElement} or
173	* {@code toElement} cannot be compared to elements currently in
174	* the set.
175	* @throws NullPointerException if {@code fromElement} or
176	* {@code toElement} is null and this set does
177	* not permit null elements
178	* @throws IllegalArgumentException if {@code fromElement} is
179	* greater than {@code toElement}; or if this set itself
180	* has a restricted range, and {@code fromElement} or
181	* {@code toElement} lies outside the bounds of the range.
182	*/
183	NavigableSet<E> subSet(E fromElement, boolean fromInclusive,
184	E toElement, boolean toInclusive);
185
186	/**
187	* Returns a view of the portion of this set whose elements are less than
188	* (or equal to, if {@code inclusive} is true) {@code toElement}. The
189	* returned set is backed by this set, so changes in the returned set are
190	* reflected in this set, and vice-versa. The returned set supports all
191	* optional set operations that this set supports.
192	*
193	* <p>The returned set will throw an {@code IllegalArgumentException}
194	* on an attempt to insert an element outside its range.
195	*
196	* @param toElement high endpoint of the returned set
197	* @param inclusive true if the high endpoint ({@code toElement}) is
198	* to be included in the returned view
199	* @return a view of the portion of this set whose elements are less than
200	* (or equal to, if {@code inclusive} is true) {@code toElement}
201	* @throws ClassCastException if {@code toElement} is not compatible
202	* with this set's comparator (or, if the set has no comparator,
203	* if {@code toElement} does not implement {@link Comparable}).
204	* Implementations may, but are not required to, throw this
205	* exception if {@code toElement} cannot be compared to elements
206	* currently in the set.
207	* @throws NullPointerException if {@code toElement} is null and
208	* this set does not permit null elements
209	* @throws IllegalArgumentException if this set itself has a
210	* restricted range, and {@code toElement} lies outside the
211	* bounds of the range
212	*/
213	NavigableSet<E> headSet(E toElement, boolean inclusive);
214
215	/**
216	* Returns a view of the portion of this set whose elements are greater
217	* than (or equal to, if {@code inclusive} is true) {@code fromElement}.
218	* The returned set is backed by this set, so changes in the returned set
219	* are reflected in this set, and vice-versa. The returned set supports
220	* all optional set operations that this set supports.
221	*
222	* <p>The returned set will throw an {@code IllegalArgumentException}
223	* on an attempt to insert an element outside its range.
224	*
225	* @param fromElement low endpoint of the returned set
226	* @param inclusive true if the low endpoint ({@code fromElement}) is
227	* to be included in the returned view
228	* @return a view of the portion of this set whose elements are greater
229	* than or equal to {@code fromElement}
230	* @throws ClassCastException if {@code fromElement} is not compatible
231	* with this set's comparator (or, if the set has no comparator,
232	* if {@code fromElement} does not implement {@link Comparable}).
233	* Implementations may, but are not required to, throw this
234	* exception if {@code fromElement} cannot be compared to elements
235	* currently in the set.
236	* @throws NullPointerException if {@code fromElement} is null
237	* and this set does not permit null elements
238	* @throws IllegalArgumentException if this set itself has a
239	* restricted range, and {@code fromElement} lies outside the
240	* bounds of the range
241	*/
242	NavigableSet<E> tailSet(E fromElement, boolean inclusive);
243	}