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>.
 *
 * <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
 */
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 o 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 o cannot be compared with the elements
     *            currently in the set.
     * @throws NullPointerException if o is <tt>null</tt> 
     * and this set deas not permit <tt>null</tt> elements
     */
    public E ceiling(E o);

    /**
     * Returns an element strictly less than the given element, or
     * <tt>null</tt> if there is no such element.
     * 
     * @param o 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 o cannot be compared with the elements
     *            currently in the set.
     * @throws NullPointerException if o is <tt>null</tt>
     * and this set deas not permit <tt>null</tt> elements
     */
    public E lower(E o);

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

    /**
     * Returns an element strictly greater than the given element, or
     * <tt>null</tt> if there is no such element.
     * 
     * @param o 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 o cannot be compared with the elements
     *            currently in the set.
     * @throws NullPointerException if o is <tt>null</tt>
     * and this set deas not permit <tt>null</tt> elements
     */
    public E higher(E o);

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

    /**
     * Retrieves and removes the last (highest) element.
     *
     * @return the last element, or <tt>null</tt> if empty.
     */
    public 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
     * 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
     *         <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 deas not permit <tt>null</tt> elements
     */
    public NavigableSet<E> subSet(E fromElement, E toElement);

    /**
     * Returns a view of the portion of this set whose elements are strictly
     * less than <tt>toElement</tt>.  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 <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 deas not permit <tt>null</tt> elements
     */
    public NavigableSet<E> headSet(E toElement);

    /**
     * Returns a view of the portion of this set whose elements are
     * greater than or equal to <tt>fromElement</tt>.  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 <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 deas not permit <tt>null</tt> elements
     */
    public NavigableSet<E> tailSet(E fromElement);
}
Revision:	1.1
Committed:	Tue Dec 28 12:14:07 2004 UTC (19 years, 4 months ago) by dl
Branch:	MAIN
Log Message:	Prepare jsr166x classes for Mustang integration
#	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	*
25	* <p> The return values of navigation methods may be ambiguous in
26	* implementations that permit <tt>null</tt> elements. However, even
27	* in this case the result can be disambiguated by checking
28	* <tt>contains(null)</tt>. To avoid such issues, implementations of
29	* this interface are encouraged <em>not</em> to permit insertion of
30	* <tt>null</tt> elements. (Note that sorted sets of {@link
31	* Comparable} elements intrinsically do not permit <tt>null</tt>.)
32	*
33	* @author Doug Lea
34	* @param <E> the type of elements maintained by this set
35	*/
36	public interface NavigableSet<E> extends SortedSet<E> {
37	/**
38	* Returns an element greater than or equal to the given element, or
39	* <tt>null</tt> if there is no such element.
40	*
41	* @param o the value to match
42	* @return an element greater than or equal to given element, or
43	* <tt>null</tt> if there is no such element.
44	* @throws ClassCastException if o cannot be compared with the elements
45	* currently in the set.
46	* @throws NullPointerException if o is <tt>null</tt>
47	* and this set deas not permit <tt>null</tt> elements
48	*/
49	public E ceiling(E o);
50
51	/**
52	* Returns an element strictly less than the given element, or
53	* <tt>null</tt> if there is no such element.
54	*
55	* @param o the value to match
56	* @return the greatest element less than the given element, or
57	* <tt>null</tt> if there is no such element.
58	* @throws ClassCastException if o cannot be compared with the elements
59	* currently in the set.
60	* @throws NullPointerException if o is <tt>null</tt>
61	* and this set deas not permit <tt>null</tt> elements
62	*/
63	public E lower(E o);
64
65	/**
66	* Returns an element less than or equal to the given element, or
67	* <tt>null</tt> if there is no such element.
68	*
69	* @param o the value to match
70	* @return the greatest element less than or equal to given
71	* element, or <tt>null</tt> if there is no such element.
72	* @throws ClassCastException if o cannot be compared with the elements
73	* currently in the set.
74	* @throws NullPointerException if o is <tt>null</tt>.
75	* and this set deas not permit <tt>null</tt> elements
76	*/
77	public E floor(E o);
78
79	/**
80	* Returns an element strictly greater than the given element, or
81	* <tt>null</tt> if there is no such element.
82	*
83	* @param o the value to match
84	* @return the least element greater than the given element, or
85	* <tt>null</tt> if there is no such element.
86	* @throws ClassCastException if o cannot be compared with the elements
87	* currently in the set.
88	* @throws NullPointerException if o is <tt>null</tt>
89	* and this set deas not permit <tt>null</tt> elements
90	*/
91	public E higher(E o);
92
93	/**
94	* Retrieves and removes the first (lowest) element.
95	*
96	* @return the first element, or <tt>null</tt> if empty.
97	*/
98	public E pollFirst();
99
100	/**
101	* Retrieves and removes the last (highest) element.
102	*
103	* @return the last element, or <tt>null</tt> if empty.
104	*/
105	public E pollLast();
106
107	/**
108	* Returns an iterator over the elements in this collection, in
109	* descending order.
110	*
111	* @return an <tt>Iterator</tt> over the elements in this collection
112	*/
113	Iterator<E> descendingIterator();
114
115	/**
116	* Returns a view of the portion of this set whose elements range from
117	* <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>, exclusive. (If
118	* <tt>fromElement</tt> and <tt>toElement</tt> are equal, the returned
119	* sorted set is empty.) The returned sorted set is backed by this set,
120	* so changes in the returned sorted set are reflected in this set, and
121	* vice-versa.
122	* @param fromElement low endpoint (inclusive) of the subSet.
123	* @param toElement high endpoint (exclusive) of the subSet.
124	* @return a view of the portion of this set whose elements range from
125	* <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>,
126	* exclusive.
127	* @throws ClassCastException if <tt>fromElement</tt> and
128	* <tt>toElement</tt> cannot be compared to one another using
129	* this set's comparator (or, if the set has no comparator,
130	* using natural ordering).
131	* @throws IllegalArgumentException if <tt>fromElement</tt> is
132	* greater than <tt>toElement</tt>.
133	* @throws NullPointerException if <tt>fromElement</tt> or
134	* <tt>toElement</tt> is <tt>null</tt>
135	* and this set deas not permit <tt>null</tt> elements
136	*/
137	public NavigableSet<E> subSet(E fromElement, E toElement);
138
139	/**
140	* Returns a view of the portion of this set whose elements are strictly
141	* less than <tt>toElement</tt>. The returned sorted set is backed by
142	* this set, so changes in the returned sorted set are reflected in this
143	* set, and vice-versa.
144	* @param toElement high endpoint (exclusive) of the headSet.
145	* @return a view of the portion of this set whose elements are strictly
146	* less than toElement.
147	* @throws ClassCastException if <tt>toElement</tt> is not compatible
148	* with this set's comparator (or, if the set has no comparator,
149	* if <tt>toElement</tt> does not implement <tt>Comparable</tt>).
150	* @throws NullPointerException if <tt>toElement</tt> is <tt>null</tt>
151	* and this set deas not permit <tt>null</tt> elements
152	*/
153	public NavigableSet<E> headSet(E toElement);
154
155	/**
156	* Returns a view of the portion of this set whose elements are
157	* greater than or equal to <tt>fromElement</tt>. The returned
158	* sorted set is backed by this set, so changes in the returned
159	* sorted set are reflected in this set, and vice-versa.
160	* @param fromElement low endpoint (inclusive) of the tailSet.
161	* @return a view of the portion of this set whose elements are
162	* greater than or equal to <tt>fromElement</tt>.
163	* @throws ClassCastException if <tt>fromElement</tt> is not
164	* compatible with this set's comparator (or, if the set has no
165	* comparator, if <tt>fromElement</tt> does not implement
166	* <tt>Comparable</tt>).
167	* @throws NullPointerException if <tt>fromElement</tt> is <tt>null</tt>
168	* and this set deas not permit <tt>null</tt> elements
169	*/
170	public NavigableSet<E> tailSet(E fromElement);
171	}