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1 : dl 1.1 /*
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 : dl 1.4 * 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 : dl 1.1 *
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 : jsr166 1.8 * <p>This interface is a member of the
38 :     * <a href="{@docRoot}/../guide/collections/index.html">
39 :     * Java Collections Framework</a>.
40 :     *
41 : dl 1.1 * @author Doug Lea
42 :     * @param <E> the type of elements maintained by this set
43 : jsr166 1.7 * @since 1.6
44 : dl 1.1 */
45 :     public interface NavigableSet<E> extends SortedSet<E> {
46 :     /**
47 :     * Returns an element greater than or equal to the given element, or
48 :     * <tt>null</tt> if there is no such element.
49 : jsr166 1.6 *
50 : jsr166 1.5 * @param e the value to match
51 : dl 1.1 * @return an element greater than or equal to given element, or
52 :     * <tt>null</tt> if there is no such element.
53 : jsr166 1.5 * @throws ClassCastException if e cannot be compared with the elements
54 : dl 1.1 * currently in the set.
55 : jsr166 1.6 * @throws NullPointerException if e is <tt>null</tt>
56 : dl 1.2 * and this set does not permit <tt>null</tt> elements
57 : dl 1.1 */
58 : jsr166 1.5 E ceiling(E e);
59 : dl 1.1
60 :     /**
61 :     * Returns an element strictly less than the given element, or
62 :     * <tt>null</tt> if there is no such element.
63 : jsr166 1.6 *
64 : jsr166 1.5 * @param e the value to match
65 : dl 1.1 * @return the greatest element less than the given element, or
66 :     * <tt>null</tt> if there is no such element.
67 : jsr166 1.5 * @throws ClassCastException if e cannot be compared with the elements
68 : dl 1.1 * currently in the set.
69 : jsr166 1.5 * @throws NullPointerException if e is <tt>null</tt>
70 : dl 1.2 * and this set does not permit <tt>null</tt> elements
71 : dl 1.1 */
72 : jsr166 1.5 E lower(E e);
73 : dl 1.1
74 :     /**
75 :     * Returns an element less than or equal to the given element, or
76 :     * <tt>null</tt> if there is no such element.
77 : jsr166 1.6 *
78 : jsr166 1.5 * @param e the value to match
79 : dl 1.1 * @return the greatest element less than or equal to given
80 :     * element, or <tt>null</tt> if there is no such element.
81 : jsr166 1.5 * @throws ClassCastException if e cannot be compared with the elements
82 : dl 1.1 * currently in the set.
83 : jsr166 1.5 * @throws NullPointerException if e is <tt>null</tt>.
84 : dl 1.2 * and this set does not permit <tt>null</tt> elements
85 : dl 1.1 */
86 : jsr166 1.5 E floor(E e);
87 : dl 1.1
88 :     /**
89 :     * Returns an element strictly greater than the given element, or
90 :     * <tt>null</tt> if there is no such element.
91 : jsr166 1.6 *
92 : jsr166 1.5 * @param e the value to match
93 : dl 1.1 * @return the least element greater than the given element, or
94 :     * <tt>null</tt> if there is no such element.
95 : jsr166 1.5 * @throws ClassCastException if e cannot be compared with the elements
96 : dl 1.1 * currently in the set.
97 : jsr166 1.5 * @throws NullPointerException if e is <tt>null</tt>
98 : dl 1.2 * and this set does not permit <tt>null</tt> elements
99 : dl 1.1 */
100 : jsr166 1.5 E higher(E e);
101 : dl 1.1
102 :     /**
103 :     * Retrieves and removes the first (lowest) element.
104 :     *
105 :     * @return the first element, or <tt>null</tt> if empty.
106 :     */
107 : dl 1.3 E pollFirst();
108 : dl 1.1
109 :     /**
110 :     * Retrieves and removes the last (highest) element.
111 :     *
112 :     * @return the last element, or <tt>null</tt> if empty.
113 :     */
114 : dl 1.3 E pollLast();
115 : dl 1.1
116 :     /**
117 :     * Returns an iterator over the elements in this collection, in
118 : jsr166 1.6 * descending order.
119 :     *
120 : dl 1.1 * @return an <tt>Iterator</tt> over the elements in this collection
121 :     */
122 :     Iterator<E> descendingIterator();
123 :    
124 :     /**
125 : dl 1.3 * Returns a view of the portion of this set whose elements range
126 :     * from <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>,
127 :     * exclusive. (If <tt>fromElement</tt> and <tt>toElement</tt> are
128 :     * equal, the returned navigable set is empty.) The returned
129 :     * navigable set is backed by this set, so changes in the returned
130 : jsr166 1.6 * navigable set are reflected in this set, and vice-versa.
131 : dl 1.3 *
132 : dl 1.1 * @param fromElement low endpoint (inclusive) of the subSet.
133 :     * @param toElement high endpoint (exclusive) of the subSet.
134 :     * @return a view of the portion of this set whose elements range from
135 :     * <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>,
136 :     * exclusive.
137 :     * @throws ClassCastException if <tt>fromElement</tt> and
138 :     * <tt>toElement</tt> cannot be compared to one another using
139 :     * this set's comparator (or, if the set has no comparator,
140 :     * using natural ordering).
141 :     * @throws IllegalArgumentException if <tt>fromElement</tt> is
142 :     * greater than <tt>toElement</tt>.
143 :     * @throws NullPointerException if <tt>fromElement</tt> or
144 : jsr166 1.6 * <tt>toElement</tt> is <tt>null</tt>
145 : dl 1.2 * and this set does not permit <tt>null</tt> elements
146 : dl 1.1 */
147 : dl 1.3 NavigableSet<E> navigableSubSet(E fromElement, E toElement);
148 : dl 1.1
149 :     /**
150 : dl 1.3 * Returns a view of the portion of this set whose elements are
151 :     * strictly less than <tt>toElement</tt>. The returned navigable
152 :     * set is backed by this set, so changes in the returned navigable
153 :     * set are reflected in this set, and vice-versa.
154 : dl 1.1 * @param toElement high endpoint (exclusive) of the headSet.
155 :     * @return a view of the portion of this set whose elements are strictly
156 :     * less than toElement.
157 :     * @throws ClassCastException if <tt>toElement</tt> is not compatible
158 :     * with this set's comparator (or, if the set has no comparator,
159 :     * if <tt>toElement</tt> does not implement <tt>Comparable</tt>).
160 :     * @throws NullPointerException if <tt>toElement</tt> is <tt>null</tt>
161 : dl 1.2 * and this set does not permit <tt>null</tt> elements
162 : dl 1.1 */
163 : dl 1.3 NavigableSet<E> navigableHeadSet(E toElement);
164 : dl 1.1
165 :     /**
166 :     * Returns a view of the portion of this set whose elements are
167 :     * greater than or equal to <tt>fromElement</tt>. The returned
168 : dl 1.3 * navigable set is backed by this set, so changes in the returned
169 :     * navigable set are reflected in this set, and vice-versa.
170 : dl 1.1 * @param fromElement low endpoint (inclusive) of the tailSet.
171 :     * @return a view of the portion of this set whose elements are
172 :     * greater than or equal to <tt>fromElement</tt>.
173 :     * @throws ClassCastException if <tt>fromElement</tt> is not
174 :     * compatible with this set's comparator (or, if the set has no
175 :     * comparator, if <tt>fromElement</tt> does not implement
176 :     * <tt>Comparable</tt>).
177 :     * @throws NullPointerException if <tt>fromElement</tt> is <tt>null</tt>
178 : dl 1.2 * and this set does not permit <tt>null</tt> elements
179 : dl 1.1 */
180 : dl 1.3 NavigableSet<E> navigableTailSet(E fromElement);
181 : dl 1.1 }

Doug Lea
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