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| 1 | /* | ||
| 2 | * Copyright (c) 1998, 2006, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package java.util; | ||
| 27 | |||
| 28 | /** | ||
| 29 | * A {@link Set} that further provides a <i>total ordering</i> on its elements. | ||
| 30 | * The elements are ordered using their {@linkplain Comparable natural | ||
| 31 | * ordering}, or by a {@link Comparator} typically provided at sorted | ||
| 32 | * set creation time. The set's iterator will traverse the set in | ||
| 33 | * ascending element order. Several additional operations are provided | ||
| 34 | * to take advantage of the ordering. (This interface is the set | ||
| 35 | * analogue of {@link SortedMap}.) | ||
| 36 | * | ||
| 37 | * <p>All elements inserted into a sorted set must implement the <tt>Comparable</tt> | ||
| 38 | * interface (or be accepted by the specified comparator). Furthermore, all | ||
| 39 | * such elements must be <i>mutually comparable</i>: <tt>e1.compareTo(e2)</tt> | ||
| 40 | * (or <tt>comparator.compare(e1, e2)</tt>) must not throw a | ||
| 41 | * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and <tt>e2</tt> in | ||
| 42 | * the sorted set. Attempts to violate this restriction will cause the | ||
| 43 | * offending method or constructor invocation to throw a | ||
| 44 | * <tt>ClassCastException</tt>. | ||
| 45 | * | ||
| 46 | * <p>Note that the ordering maintained by a sorted set (whether or not an | ||
| 47 | * explicit comparator is provided) must be <i>consistent with equals</i> if | ||
| 48 | * the sorted set is to correctly implement the <tt>Set</tt> interface. (See | ||
| 49 | * the <tt>Comparable</tt> interface or <tt>Comparator</tt> interface for a | ||
| 50 | * precise definition of <i>consistent with equals</i>.) This is so because | ||
| 51 | * the <tt>Set</tt> interface is defined in terms of the <tt>equals</tt> | ||
| 52 | * operation, but a sorted set performs all element comparisons using its | ||
| 53 | * <tt>compareTo</tt> (or <tt>compare</tt>) method, so two elements that are | ||
| 54 | * deemed equal by this method are, from the standpoint of the sorted set, | ||
| 55 | * equal. The behavior of a sorted set <i>is</i> well-defined even if its | ||
| 56 | * ordering is inconsistent with equals; it just fails to obey the general | ||
| 57 | * contract of the <tt>Set</tt> interface. | ||
| 58 | * | ||
| 59 | * <p>All general-purpose sorted set implementation classes should | ||
| 60 | * provide four "standard" constructors: 1) A void (no arguments) | ||
| 61 | * constructor, which creates an empty sorted set sorted according to | ||
| 62 | * the natural ordering of its elements. 2) A constructor with a | ||
| 63 | * single argument of type <tt>Comparator</tt>, which creates an empty | ||
| 64 | * sorted set sorted according to the specified comparator. 3) A | ||
| 65 | * constructor with a single argument of type <tt>Collection</tt>, | ||
| 66 | * which creates a new sorted set with the same elements as its | ||
| 67 | * argument, sorted according to the natural ordering of the elements. | ||
| 68 | * 4) A constructor with a single argument of type <tt>SortedSet</tt>, | ||
| 69 | * which creates a new sorted set with the same elements and the same | ||
| 70 | * ordering as the input sorted set. There is no way to enforce this | ||
| 71 | * recommendation, as interfaces cannot contain constructors. | ||
| 72 | * | ||
| 73 | * <p>Note: several methods return subsets with restricted ranges. | ||
| 74 | * Such ranges are <i>half-open</i>, that is, they include their low | ||
| 75 | * endpoint but not their high endpoint (where applicable). | ||
| 76 | * If you need a <i>closed range</i> (which includes both endpoints), and | ||
| 77 | * the element type allows for calculation of the successor of a given | ||
| 78 | * value, merely request the subrange from <tt>lowEndpoint</tt> to | ||
| 79 | * <tt>successor(highEndpoint)</tt>. For example, suppose that <tt>s</tt> | ||
| 80 | * is a sorted set of strings. The following idiom obtains a view | ||
| 81 | * containing all of the strings in <tt>s</tt> from <tt>low</tt> to | ||
| 82 | * <tt>high</tt>, inclusive:<pre> | ||
| 83 | * SortedSet<String> sub = s.subSet(low, high+"\0");</pre> | ||
| 84 | * | ||
| 85 | * A similar technique can be used to generate an <i>open range</i> (which | ||
| 86 | * contains neither endpoint). The following idiom obtains a view | ||
| 87 | * containing all of the Strings in <tt>s</tt> from <tt>low</tt> to | ||
| 88 | * <tt>high</tt>, exclusive:<pre> | ||
| 89 | * SortedSet<String> sub = s.subSet(low+"\0", high);</pre> | ||
| 90 | * | ||
| 91 | * <p>This interface is a member of the | ||
| 92 | * <a href="{@docRoot}/../technotes/guides/collections/index.html"> | ||
| 93 | * Java Collections Framework</a>. | ||
| 94 | * | ||
| 95 | * @param <E> the type of elements maintained by this set | ||
| 96 | * | ||
| 97 | * @author Josh Bloch | ||
| 98 | * @see Set | ||
| 99 | * @see TreeSet | ||
| 100 | * @see SortedMap | ||
| 101 | * @see Collection | ||
| 102 | * @see Comparable | ||
| 103 | * @see Comparator | ||
| 104 | * @see ClassCastException | ||
| 105 | * @since 1.2 | ||
| 106 | */ | ||
| 107 | |||
| 108 | public interface SortedSet<E> extends Set<E> { | ||
| 109 | /** | ||
| 110 | * Returns the comparator used to order the elements in this set, | ||
| 111 | * or <tt>null</tt> if this set uses the {@linkplain Comparable | ||
| 112 | * natural ordering} of its elements. | ||
| 113 | * | ||
| 114 | * @return the comparator used to order the elements in this set, | ||
| 115 | * or <tt>null</tt> if this set uses the natural ordering | ||
| 116 | * of its elements | ||
| 117 | */ | ||
| 118 | Comparator<? super E> comparator(); | ||
| 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 set is empty.) The returned set is backed | ||
| 125 | * by this set, so changes in the returned set are reflected in | ||
| 126 | * this set, and vice-versa. The returned set supports all | ||
| 127 | * optional set operations that this set supports. | ||
| 128 | * | ||
| 129 | * <p>The returned set will throw an <tt>IllegalArgumentException</tt> | ||
| 130 | * on an attempt to insert an element outside its range. | ||
| 131 | * | ||
| 132 | * @param fromElement low endpoint (inclusive) of the returned set | ||
| 133 | * @param toElement high endpoint (exclusive) of the returned set | ||
| 134 | * @return a view of the portion of this set whose elements range from | ||
| 135 | * <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>, exclusive | ||
| 136 | * @throws ClassCastException if <tt>fromElement</tt> and | ||
| 137 | * <tt>toElement</tt> cannot be compared to one another using this | ||
| 138 | * set's comparator (or, if the set has no comparator, using | ||
| 139 | * natural ordering). Implementations may, but are not required | ||
| 140 | * to, throw this exception if <tt>fromElement</tt> or | ||
| 141 | * <tt>toElement</tt> cannot be compared to elements currently in | ||
| 142 | * the set. | ||
| 143 | * @throws NullPointerException if <tt>fromElement</tt> or | ||
| 144 | * <tt>toElement</tt> is null and this set does not permit null | ||
| 145 | * elements | ||
| 146 | * @throws IllegalArgumentException if <tt>fromElement</tt> is | ||
| 147 | * greater than <tt>toElement</tt>; or if this set itself | ||
| 148 | * has a restricted range, and <tt>fromElement</tt> or | ||
| 149 | * <tt>toElement</tt> lies outside the bounds of the range | ||
| 150 | */ | ||
| 151 | SortedSet<E> subSet(E fromElement, E toElement); | ||
| 152 | |||
| 153 | /** | ||
| 154 | * Returns a view of the portion of this set whose elements are | ||
| 155 | * strictly less than <tt>toElement</tt>. The returned set is | ||
| 156 | * backed by this set, so changes in the returned set are | ||
| 157 | * reflected in this set, and vice-versa. The returned set | ||
| 158 | * supports all optional set operations that this set supports. | ||
| 159 | * | ||
| 160 | * <p>The returned set will throw an <tt>IllegalArgumentException</tt> | ||
| 161 | * on an attempt to insert an element outside its range. | ||
| 162 | * | ||
| 163 | * @param toElement high endpoint (exclusive) of the returned set | ||
| 164 | * @return a view of the portion of this set whose elements are strictly | ||
| 165 | * less than <tt>toElement</tt> | ||
| 166 | * @throws ClassCastException if <tt>toElement</tt> is not compatible | ||
| 167 | * with this set's comparator (or, if the set has no comparator, | ||
| 168 | * if <tt>toElement</tt> does not implement {@link Comparable}). | ||
| 169 | * Implementations may, but are not required to, throw this | ||
| 170 | * exception if <tt>toElement</tt> cannot be compared to elements | ||
| 171 | * currently in the set. | ||
| 172 | * @throws NullPointerException if <tt>toElement</tt> is null and | ||
| 173 | * this set does not permit null elements | ||
| 174 | * @throws IllegalArgumentException if this set itself has a | ||
| 175 | * restricted range, and <tt>toElement</tt> lies outside the | ||
| 176 | * bounds of the range | ||
| 177 | */ | ||
| 178 | SortedSet<E> headSet(E toElement); | ||
| 179 | |||
| 180 | /** | ||
| 181 | * Returns a view of the portion of this set whose elements are | ||
| 182 | * greater than or equal to <tt>fromElement</tt>. The returned | ||
| 183 | * set is backed by this set, so changes in the returned set are | ||
| 184 | * reflected in this set, and vice-versa. The returned set | ||
| 185 | * supports all optional set operations that this set supports. | ||
| 186 | * | ||
| 187 | * <p>The returned set will throw an <tt>IllegalArgumentException</tt> | ||
| 188 | * on an attempt to insert an element outside its range. | ||
| 189 | * | ||
| 190 | * @param fromElement low endpoint (inclusive) of the returned set | ||
| 191 | * @return a view of the portion of this set whose elements are greater | ||
| 192 | * than or equal to <tt>fromElement</tt> | ||
| 193 | * @throws ClassCastException if <tt>fromElement</tt> is not compatible | ||
| 194 | * with this set's comparator (or, if the set has no comparator, | ||
| 195 | * if <tt>fromElement</tt> does not implement {@link Comparable}). | ||
| 196 | * Implementations may, but are not required to, throw this | ||
| 197 | * exception if <tt>fromElement</tt> cannot be compared to elements | ||
| 198 | * currently in the set. | ||
| 199 | * @throws NullPointerException if <tt>fromElement</tt> is null | ||
| 200 | * and this set does not permit null elements | ||
| 201 | * @throws IllegalArgumentException if this set itself has a | ||
| 202 | * restricted range, and <tt>fromElement</tt> lies outside the | ||
| 203 | * bounds of the range | ||
| 204 | */ | ||
| 205 | SortedSet<E> tailSet(E fromElement); | ||
| 206 | |||
| 207 | /** | ||
| 208 | * Returns the first (lowest) element currently in this set. | ||
| 209 | * | ||
| 210 | * @return the first (lowest) element currently in this set | ||
| 211 | * @throws NoSuchElementException if this set is empty | ||
| 212 | */ | ||
| 213 | E first(); | ||
| 214 | |||
| 215 | /** | ||
| 216 | * Returns the last (highest) element currently in this set. | ||
| 217 | * | ||
| 218 | * @return the last (highest) element currently in this set | ||
| 219 | * @throws NoSuchElementException if this set is empty | ||
| 220 | */ | ||
| 221 | E last(); | ||
| 222 | } | ||