src/jsr166x/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/publicdomain/zero/1.0/
 */

package jsr166x;

import java.util.*;

/**
 * A {@link SortedSet} extended with navigation methods reporting
 * closest matches for given search targets. Methods {@code lower},
 * {@code floor}, {@code ceiling}, and {@code higher} return 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.  A {@code NavigableSet} may be viewed and traversed
 * in either ascending or descending order.  The {@code Collection}
 * {@code iterator} method returns an ascending {@code Iterator} and
 * the additional method {@code descendingIterator} returns
 * descending iterator. The performance of ascending traversals is
 * likely to be faster than descending traversals.  This interface
 * additionally defines methods {@code pollFirst} and
 * {@code pollLast} that return and remove the lowest and highest key,
 * if one exists, else returning {@code null}.
 *
 * <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 <em>not</em> to permit insertion of
 * {@code null} elements. (Note that sorted sets of {@link
 * Comparable} elements intrinsically do not permit {@code null}.)
 *
 * @author Doug Lea
 * @param <E> the type of elements maintained by this set
 */
public interface NavigableSet<E> extends SortedSet<E> {
    /**
     * Returns an element greater than or equal to the given element, or
     * {@code null} if there is no such element.
     *
     * @param o the value to match
     * @return an element greater than or equal to given element, or
     * {@code null} if there is no such element
     * @throws ClassCastException if o cannot be compared with the elements
     *            currently in the set
     * @throws NullPointerException if o is {@code null}
     * and this set deas not permit {@code null} elements
     */
    public E ceiling(E o);

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

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

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

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

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

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

    /**
     * Returns a view of the portion of this set whose elements range from
     * {@code fromElement}, inclusive, to {@code toElement}, exclusive.  (If
     * {@code fromElement} and {@code toElement} are equal, the returned
     * sorted set is empty.)  The returned sorted set is backed by this set,
     * so changes in the returned sorted 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
     *         {@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)
     * @throws IllegalArgumentException if {@code fromElement} is
     * greater than {@code toElement}
     * @throws NullPointerException if {@code fromElement} or
     *         {@code toElement} is {@code null}
     * and this set deas not permit {@code null} elements
     */
    public NavigableSet<E> subSet(E fromElement, E toElement);

    /**
     * Returns a view of the portion of this set whose elements are strictly
     * less than {@code toElement}.  The returned sorted set is backed by
     * this set, so changes in the returned sorted 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 {@code toElement} is not compatible
     *         with this set's comparator (or, if the set has no comparator,
     *         if {@code toElement} does not implement {@code Comparable})
     * @throws NullPointerException if {@code toElement} is {@code null}
     * and this set deas not permit {@code null} elements
     */
    public NavigableSet<E> headSet(E toElement);

    /**
     * Returns a view of the portion of this set whose elements are
     * greater than or equal to {@code fromElement}.  The returned
     * sorted set is backed by this set, so changes in the returned
     * sorted 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 {@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
     * {@code Comparable})
     * @throws NullPointerException if {@code fromElement} is {@code null}
     * and this set deas not permit {@code null} elements
     */
    public NavigableSet<E> tailSet(E fromElement);
}
Revision:	1.12
Committed:	Sun Jan 18 20:17:33 2015 UTC (9 years, 3 months ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.11:	+1 -0 lines
Log Message:	exactly one blank line before and after package statements
#	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/publicdomain/zero/1.0/
5	*/
6
7	package jsr166x;
8
9	import java.util.*;
10
11	/**
12	* A {@link SortedSet} extended with navigation methods reporting
13	* closest matches for given search targets. Methods {@code lower},
14	* {@code floor}, {@code ceiling}, and {@code higher} return keys
15	* respectively less than, less than or equal, greater than or equal,
16	* and greater than a given key, returning {@code null} if there is
17	* no such key. A {@code NavigableSet} may be viewed and traversed
18	* in either ascending or descending order. The {@code Collection}
19	* {@code iterator} method returns an ascending {@code Iterator} and
20	* the additional method {@code descendingIterator} returns
21	* descending iterator. The performance of ascending traversals is
22	* likely to be faster than descending traversals. This interface
23	* additionally defines methods {@code pollFirst} and
24	* {@code pollLast} that return and remove the lowest and highest key,
25	* if one exists, else returning {@code null}.
26	*
27	* <p>The return values of navigation methods may be ambiguous in
28	* implementations that permit {@code null} elements. However, even
29	* in this case the result can be disambiguated by checking
30	* {@code contains(null)}. To avoid such issues, implementations of
31	* this interface are encouraged <em>not</em> to permit insertion of
32	* {@code null} elements. (Note that sorted sets of {@link
33	* Comparable} elements intrinsically do not permit {@code null}.)
34	*
35	* @author Doug Lea
36	* @param <E> the type of elements maintained by this set
37	*/
38	public interface NavigableSet<E> extends SortedSet<E> {
39	/**
40	* Returns an element greater than or equal to the given element, or
41	* {@code null} if there is no such element.
42	*
43	* @param o the value to match
44	* @return an element greater than or equal to given element, or
45	* {@code null} if there is no such element
46	* @throws ClassCastException if o cannot be compared with the elements
47	* currently in the set
48	* @throws NullPointerException if o is {@code null}
49	* and this set deas not permit {@code null} elements
50	*/
51	public E ceiling(E o);
52
53	/**
54	* Returns an element strictly less than the given element, or
55	* {@code null} if there is no such element.
56	*
57	* @param o the value to match
58	* @return the greatest element less than the given element, or
59	* {@code null} if there is no such element
60	* @throws ClassCastException if o cannot be compared with the elements
61	* currently in the set
62	* @throws NullPointerException if o is {@code null}
63	* and this set deas not permit {@code null} elements
64	*/
65	public E lower(E o);
66
67	/**
68	* Returns an element less than or equal to the given element, or
69	* {@code null} if there is no such element.
70	*
71	* @param o the value to match
72	* @return the greatest element less than or equal to given
73	* element, or {@code null} if there is no such element
74	* @throws ClassCastException if o cannot be compared with the elements
75	* currently in the set
76	* @throws NullPointerException if o is {@code null}
77	* and this set deas not permit {@code null} elements
78	*/
79	public E floor(E o);
80
81	/**
82	* Returns an element strictly greater than the given element, or
83	* {@code null} if there is no such element.
84	*
85	* @param o the value to match
86	* @return the least element greater than the given element, or
87	* {@code null} if there is no such element
88	* @throws ClassCastException if o cannot be compared with the elements
89	* currently in the set
90	* @throws NullPointerException if o is {@code null}
91	* and this set deas not permit {@code null} elements
92	*/
93	public E higher(E o);
94
95	/**
96	* Retrieves and removes the first (lowest) element.
97	*
98	* @return the first element, or {@code null} if empty
99	*/
100	public E pollFirst();
101
102	/**
103	* Retrieves and removes the last (highest) element.
104	*
105	* @return the last element, or {@code null} if empty
106	*/
107	public E pollLast();
108
109	/**
110	* Returns an iterator over the elements in this collection, in
111	* descending order.
112	*
113	* @return an {@code Iterator} over the elements in this collection
114	*/
115	Iterator<E> descendingIterator();
116
117	/**
118	* Returns a view of the portion of this set whose elements range from
119	* {@code fromElement}, inclusive, to {@code toElement}, exclusive. (If
120	* {@code fromElement} and {@code toElement} are equal, the returned
121	* sorted set is empty.) The returned sorted set is backed by this set,
122	* so changes in the returned sorted set are reflected in this set, and
123	* vice-versa.
124	* @param fromElement low endpoint (inclusive) of the subSet
125	* @param toElement high endpoint (exclusive) of the subSet
126	* @return a view of the portion of this set whose elements range from
127	* {@code fromElement}, inclusive, to {@code toElement},
128	* exclusive
129	* @throws ClassCastException if {@code fromElement} and
130	* {@code toElement} cannot be compared to one another using
131	* this set's comparator (or, if the set has no comparator,
132	* using natural ordering)
133	* @throws IllegalArgumentException if {@code fromElement} is
134	* greater than {@code toElement}
135	* @throws NullPointerException if {@code fromElement} or
136	* {@code toElement} is {@code null}
137	* and this set deas not permit {@code null} elements
138	*/
139	public NavigableSet<E> subSet(E fromElement, E toElement);
140
141	/**
142	* Returns a view of the portion of this set whose elements are strictly
143	* less than {@code toElement}. The returned sorted set is backed by
144	* this set, so changes in the returned sorted set are reflected in this
145	* set, and vice-versa.
146	* @param toElement high endpoint (exclusive) of the headSet
147	* @return a view of the portion of this set whose elements are strictly
148	* less than toElement
149	* @throws ClassCastException if {@code toElement} is not compatible
150	* with this set's comparator (or, if the set has no comparator,
151	* if {@code toElement} does not implement {@code Comparable})
152	* @throws NullPointerException if {@code toElement} is {@code null}
153	* and this set deas not permit {@code null} elements
154	*/
155	public NavigableSet<E> headSet(E toElement);
156
157	/**
158	* Returns a view of the portion of this set whose elements are
159	* greater than or equal to {@code fromElement}. The returned
160	* sorted set is backed by this set, so changes in the returned
161	* sorted set are reflected in this set, and vice-versa.
162	* @param fromElement low endpoint (inclusive) of the tailSet
163	* @return a view of the portion of this set whose elements are
164	* greater than or equal to {@code fromElement}
165	* @throws ClassCastException if {@code fromElement} is not
166	* compatible with this set's comparator (or, if the set has no
167	* comparator, if {@code fromElement} does not implement
168	* {@code Comparable})
169	* @throws NullPointerException if {@code fromElement} is {@code null}
170	* and this set deas not permit {@code null} elements
171	*/
172	public NavigableSet<E> tailSet(E fromElement);
173	}