java/util/NavigableSet.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 SortedSet} extended with navigation methods reporting
 * closest matches for given search targets. Methods <tt>lower</tt>,
 * <tt>floor</tt>, <tt>ceiling</tt>, and <tt>higher</tt> return 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.  A <tt>NavigableSet</tt> may be viewed and traversed
 * in either ascending or descending order.  The <tt>Collection</tt>
 * <tt>iterator</tt> method returns an ascending <tt>Iterator</tt> and
 * the additional method <tt>descendingIterator</tt> returns
 * descending iterator. The performance of ascending traversals is
 * likely to be faster than descending traversals.  This interface
 * additionally defines methods <tt>pollFirst</tt> and
 * <t>pollLast</tt> that return and remove the lowest and highest key,
 * if one exists, else returning <tt>null</tt>.
 * Methods <tt>navigableSubSet</tt>, <tt>navigableHeadSet</tt>, and
 * <tt>navigableTailSet</tt> differ from the similarly named
 * <tt>SortedSet</tt> methods only in that the returned sets
 * are guaranteed to obey the <tt>NavigableSet</tt> interface.
 *
 * <p> The return values of navigation methods may be ambiguous in
 * implementations that permit <tt>null</tt> elements. However, even
 * in this case the result can be disambiguated by checking
 * <tt>contains(null)</tt>. To avoid such issues, implementations of
 * this interface are encouraged <em>not</em> to permit insertion of
 * <tt>null</tt> elements. (Note that sorted sets of {@link
 * Comparable} elements intrinsically do not permit <tt>null</tt>.)
 *
 * @author Doug Lea
 * @param <E> the type of elements maintained by this set
 * @since 1.6
 */
public interface NavigableSet<E> extends SortedSet<E> {
    /**
     * Returns an element greater than or equal to the given element, or
     * <tt>null</tt> if there is no such element.
     *
     * @param e the value to match
     * @return an element greater than or equal to given element, or
     * <tt>null</tt> if there is no such element.
     * @throws ClassCastException if e cannot be compared with the elements
     *            currently in the set.
     * @throws NullPointerException if e is <tt>null</tt>
     * and this set does not permit <tt>null</tt> elements
     */
    E ceiling(E e);

    /**
     * Returns an element strictly less than the given element, or
     * <tt>null</tt> if there is no such element.
     *
     * @param e the value to match
     * @return the greatest element less than the given element, or
     * <tt>null</tt> if there is no such element.
     * @throws ClassCastException if e cannot be compared with the elements
     *            currently in the set.
     * @throws NullPointerException if e is <tt>null</tt>
     * and this set does not permit <tt>null</tt> elements
     */
    E lower(E e);

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

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

    /**
     * Retrieves and removes the first (lowest) element.
     *
     * @return the first element, or <tt>null</tt> if empty.
     */
    E pollFirst();

    /**
     * Retrieves and removes the last (highest) element.
     *
     * @return the last element, or <tt>null</tt> if empty.
     */
    E pollLast();

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

    /**
     * Returns a view of the portion of this set whose elements range
     * from <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>,
     * exclusive.  (If <tt>fromElement</tt> and <tt>toElement</tt> are
     * equal, the returned navigable set is empty.)  The returned
     * navigable set is backed by this set, so changes in the returned
     * navigable set are reflected in this set, and vice-versa.
     *
     * @param fromElement low endpoint (inclusive) of the subSet.
     * @param toElement high endpoint (exclusive) of the subSet.
     * @return a view of the portion of this set whose elements range from
     *         <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>,
     *         exclusive.
     * @throws ClassCastException if <tt>fromElement</tt> and
     *         <tt>toElement</tt> cannot be compared to one another using
     *         this set's comparator (or, if the set has no comparator,
     *         using natural ordering).
     * @throws IllegalArgumentException if <tt>fromElement</tt> is
     * greater than <tt>toElement</tt>.
     * @throws NullPointerException if <tt>fromElement</tt> or
     *         <tt>toElement</tt> is <tt>null</tt>
     * and this set does not permit <tt>null</tt> elements
     */
    NavigableSet<E> navigableSubSet(E fromElement, E toElement);

    /**
     * Returns a view of the portion of this set whose elements are
     * strictly less than <tt>toElement</tt>.  The returned navigable
     * set is backed by this set, so changes in the returned navigable
     * set are reflected in this set, and vice-versa.
     * @param toElement high endpoint (exclusive) of the headSet.
     * @return a view of the portion of this set whose elements are strictly
     *         less than toElement.
     * @throws ClassCastException if <tt>toElement</tt> is not compatible
     *         with this set's comparator (or, if the set has no comparator,
     *         if <tt>toElement</tt> does not implement <tt>Comparable</tt>).
     * @throws NullPointerException if <tt>toElement</tt> is <tt>null</tt>
     * and this set does not permit <tt>null</tt> elements
     */
    NavigableSet<E> navigableHeadSet(E toElement);

    /**
     * Returns a view of the portion of this set whose elements are
     * greater than or equal to <tt>fromElement</tt>.  The returned
     * navigable set is backed by this set, so changes in the returned
     * navigable set are reflected in this set, and vice-versa.
     * @param fromElement low endpoint (inclusive) of the tailSet.
     * @return a view of the portion of this set whose elements are
     * greater than or equal to <tt>fromElement</tt>.
     * @throws ClassCastException if <tt>fromElement</tt> is not
     * compatible with this set's comparator (or, if the set has no
     * comparator, if <tt>fromElement</tt> does not implement
     * <tt>Comparable</tt>).
     * @throws NullPointerException if <tt>fromElement</tt> is <tt>null</tt>
     * and this set does not permit <tt>null</tt> elements
     */
    NavigableSet<E> navigableTailSet(E fromElement);
}
Revision:	1.7
Committed:	Mon May 2 22:34:56 2005 UTC (19 years ago) by jsr166
Branch:	MAIN
Changes since 1.6:	+1 -0 lines
Log Message:	Add missing @since 1.6
#	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 SortedSet} extended with navigation methods reporting
11	* closest matches for given search targets. Methods <tt>lower</tt>,
12	* <tt>floor</tt>, <tt>ceiling</tt>, and <tt>higher</tt> return keys
13	* respectively less than, less than or equal, greater than or equal,
14	* and greater than a given key, returning <tt>null</tt> if there is
15	* no such key. A <tt>NavigableSet</tt> may be viewed and traversed
16	* in either ascending or descending order. The <tt>Collection</tt>
17	* <tt>iterator</tt> method returns an ascending <tt>Iterator</tt> and
18	* the additional method <tt>descendingIterator</tt> returns
19	* descending iterator. The performance of ascending traversals is
20	* likely to be faster than descending traversals. This interface
21	* additionally defines methods <tt>pollFirst</tt> and
22	* <t>pollLast</tt> that return and remove the lowest and highest key,
23	* if one exists, else returning <tt>null</tt>.
24	* Methods <tt>navigableSubSet</tt>, <tt>navigableHeadSet</tt>, and
25	* <tt>navigableTailSet</tt> differ from the similarly named
26	* <tt>SortedSet</tt> methods only in that the returned sets
27	* are guaranteed to obey the <tt>NavigableSet</tt> interface.
28	*
29	* <p> The return values of navigation methods may be ambiguous in
30	* implementations that permit <tt>null</tt> elements. However, even
31	* in this case the result can be disambiguated by checking
32	* <tt>contains(null)</tt>. To avoid such issues, implementations of
33	* this interface are encouraged <em>not</em> to permit insertion of
34	* <tt>null</tt> elements. (Note that sorted sets of {@link
35	* Comparable} elements intrinsically do not permit <tt>null</tt>.)
36	*
37	* @author Doug Lea
38	* @param <E> the type of elements maintained by this set
39	* @since 1.6
40	*/
41	public interface NavigableSet<E> extends SortedSet<E> {
42	/**
43	* Returns an element greater than or equal to the given element, or
44	* <tt>null</tt> if there is no such element.
45	*
46	* @param e the value to match
47	* @return an element greater than or equal to given element, or
48	* <tt>null</tt> if there is no such element.
49	* @throws ClassCastException if e cannot be compared with the elements
50	* currently in the set.
51	* @throws NullPointerException if e is <tt>null</tt>
52	* and this set does not permit <tt>null</tt> elements
53	*/
54	E ceiling(E e);
55
56	/**
57	* Returns an element strictly less than the given element, or
58	* <tt>null</tt> if there is no such element.
59	*
60	* @param e the value to match
61	* @return the greatest element less than the given element, or
62	* <tt>null</tt> if there is no such element.
63	* @throws ClassCastException if e cannot be compared with the elements
64	* currently in the set.
65	* @throws NullPointerException if e is <tt>null</tt>
66	* and this set does not permit <tt>null</tt> elements
67	*/
68	E lower(E e);
69
70	/**
71	* Returns an element less than or equal to the given element, or
72	* <tt>null</tt> if there is no such element.
73	*
74	* @param e the value to match
75	* @return the greatest element less than or equal to given
76	* element, or <tt>null</tt> if there is no such element.
77	* @throws ClassCastException if e cannot be compared with the elements
78	* currently in the set.
79	* @throws NullPointerException if e is <tt>null</tt>.
80	* and this set does not permit <tt>null</tt> elements
81	*/
82	E floor(E e);
83
84	/**
85	* Returns an element strictly greater than the given element, or
86	* <tt>null</tt> if there is no such element.
87	*
88	* @param e the value to match
89	* @return the least element greater than the given element, or
90	* <tt>null</tt> if there is no such element.
91	* @throws ClassCastException if e cannot be compared with the elements
92	* currently in the set.
93	* @throws NullPointerException if e is <tt>null</tt>
94	* and this set does not permit <tt>null</tt> elements
95	*/
96	E higher(E e);
97
98	/**
99	* Retrieves and removes the first (lowest) element.
100	*
101	* @return the first element, or <tt>null</tt> if empty.
102	*/
103	E pollFirst();
104
105	/**
106	* Retrieves and removes the last (highest) element.
107	*
108	* @return the last element, or <tt>null</tt> if empty.
109	*/
110	E pollLast();
111
112	/**
113	* Returns an iterator over the elements in this collection, in
114	* descending order.
115	*
116	* @return an <tt>Iterator</tt> over the elements in this collection
117	*/
118	Iterator<E> descendingIterator();
119
120	/**
121	* Returns a view of the portion of this set whose elements range
122	* from <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>,
123	* exclusive. (If <tt>fromElement</tt> and <tt>toElement</tt> are
124	* equal, the returned navigable set is empty.) The returned
125	* navigable set is backed by this set, so changes in the returned
126	* navigable set are reflected in this set, and vice-versa.
127	*
128	* @param fromElement low endpoint (inclusive) of the subSet.
129	* @param toElement high endpoint (exclusive) of the subSet.
130	* @return a view of the portion of this set whose elements range from
131	* <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>,
132	* exclusive.
133	* @throws ClassCastException if <tt>fromElement</tt> and
134	* <tt>toElement</tt> cannot be compared to one another using
135	* this set's comparator (or, if the set has no comparator,
136	* using natural ordering).
137	* @throws IllegalArgumentException if <tt>fromElement</tt> is
138	* greater than <tt>toElement</tt>.
139	* @throws NullPointerException if <tt>fromElement</tt> or
140	* <tt>toElement</tt> is <tt>null</tt>
141	* and this set does not permit <tt>null</tt> elements
142	*/
143	NavigableSet<E> navigableSubSet(E fromElement, E toElement);
144
145	/**
146	* Returns a view of the portion of this set whose elements are
147	* strictly less than <tt>toElement</tt>. The returned navigable
148	* set is backed by this set, so changes in the returned navigable
149	* set are reflected in this set, and vice-versa.
150	* @param toElement high endpoint (exclusive) of the headSet.
151	* @return a view of the portion of this set whose elements are strictly
152	* less than toElement.
153	* @throws ClassCastException if <tt>toElement</tt> is not compatible
154	* with this set's comparator (or, if the set has no comparator,
155	* if <tt>toElement</tt> does not implement <tt>Comparable</tt>).
156	* @throws NullPointerException if <tt>toElement</tt> is <tt>null</tt>
157	* and this set does not permit <tt>null</tt> elements
158	*/
159	NavigableSet<E> navigableHeadSet(E toElement);
160
161	/**
162	* Returns a view of the portion of this set whose elements are
163	* greater than or equal to <tt>fromElement</tt>. The returned
164	* navigable set is backed by this set, so changes in the returned
165	* navigable set are reflected in this set, and vice-versa.
166	* @param fromElement low endpoint (inclusive) of the tailSet.
167	* @return a view of the portion of this set whose elements are
168	* greater than or equal to <tt>fromElement</tt>.
169	* @throws ClassCastException if <tt>fromElement</tt> is not
170	* compatible with this set's comparator (or, if the set has no
171	* comparator, if <tt>fromElement</tt> does not implement
172	* <tt>Comparable</tt>).
173	* @throws NullPointerException if <tt>fromElement</tt> is <tt>null</tt>
174	* and this set does not permit <tt>null</tt> elements
175	*/
176	NavigableSet<E> navigableTailSet(E fromElement);
177	}