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

Doug Lea
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