/* * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.util; /** * A {@link Set} that further provides a total ordering on its elements. * The elements are ordered using their {@linkplain Comparable natural * ordering}, or by a {@link Comparator} typically provided at sorted * set creation time. The set's iterator will traverse the set in * ascending element order. Several additional operations are provided * to take advantage of the ordering. (This interface is the set * analogue of {@link SortedMap}.) * *

All elements inserted into a sorted set must implement the Comparable * interface (or be accepted by the specified comparator). Furthermore, all * such elements must be mutually comparable: e1.compareTo(e2) * (or comparator.compare(e1, e2)) must not throw a * ClassCastException for any elements e1 and e2 in * the sorted set. Attempts to violate this restriction will cause the * offending method or constructor invocation to throw a * ClassCastException. * *

Note that the ordering maintained by a sorted set (whether or not an * explicit comparator is provided) must be consistent with equals if * the sorted set is to correctly implement the Set interface. (See * the Comparable interface or Comparator interface for a * precise definition of consistent with equals.) This is so because * the Set interface is defined in terms of the equals * operation, but a sorted set performs all element comparisons using its * compareTo (or compare) method, so two elements that are * deemed equal by this method are, from the standpoint of the sorted set, * equal. The behavior of a sorted set is well-defined even if its * ordering is inconsistent with equals; it just fails to obey the general * contract of the Set interface. * *

All general-purpose sorted set implementation classes should * provide four "standard" constructors: 1) A void (no arguments) * constructor, which creates an empty sorted set sorted according to * the natural ordering of its elements. 2) A constructor with a * single argument of type Comparator, which creates an empty * sorted set sorted according to the specified comparator. 3) A * constructor with a single argument of type Collection, * which creates a new sorted set with the same elements as its * argument, sorted according to the natural ordering of the elements. * 4) A constructor with a single argument of type SortedSet, * which creates a new sorted set with the same elements and the same * ordering as the input sorted set. There is no way to enforce this * recommendation, as interfaces cannot contain constructors. * *

Note: several methods return subsets with restricted ranges. * Such ranges are half-open, that is, they include their low * endpoint but not their high endpoint (where applicable). * If you need a closed range (which includes both endpoints), and * the element type allows for calculation of the successor of a given * value, merely request the subrange from lowEndpoint to * successor(highEndpoint). For example, suppose that s * is a sorted set of strings. The following idiom obtains a view * containing all of the strings in s from low to * high, inclusive:

 *   SortedSet<String> sub = s.subSet(low, high+"\0");
* * A similar technique can be used to generate an open range (which * contains neither endpoint). The following idiom obtains a view * containing all of the Strings in s from low to * high, exclusive:
 *   SortedSet<String> sub = s.subSet(low+"\0", high);
* *

This interface is a member of the * * Java Collections Framework. * * @param the type of elements maintained by this set * * @author Josh Bloch * @see Set * @see TreeSet * @see SortedMap * @see Collection * @see Comparable * @see Comparator * @see ClassCastException * @since 1.2 */ public interface SortedSet extends Set { /** * Returns the comparator used to order the elements in this set, * or null if this set uses the {@linkplain Comparable * natural ordering} of its elements. * * @return the comparator used to order the elements in this set, * or null if this set uses the natural ordering * of its elements */ Comparator comparator(); /** * Returns a view of the portion of this set whose elements range * from fromElement, inclusive, to toElement, * exclusive. (If fromElement and toElement are * equal, the returned set is empty.) The returned set is backed * by this set, so changes in the returned set are reflected in * this set, and vice-versa. The returned set supports all * optional set operations that this set supports. * *

The returned set will throw an IllegalArgumentException * on an attempt to insert an element outside its range. * * @param fromElement low endpoint (inclusive) of the returned set * @param toElement high endpoint (exclusive) of the returned set * @return a view of the portion of this set whose elements range from * fromElement, inclusive, to toElement, exclusive * @throws ClassCastException if fromElement and * toElement cannot be compared to one another using this * set's comparator (or, if the set has no comparator, using * natural ordering). Implementations may, but are not required * to, throw this exception if fromElement or * toElement cannot be compared to elements currently in * the set. * @throws NullPointerException if fromElement or * toElement is null and this set does not permit null * elements * @throws IllegalArgumentException if fromElement is * greater than toElement; or if this set itself * has a restricted range, and fromElement or * toElement lies outside the bounds of the range */ SortedSet subSet(E fromElement, E toElement); /** * Returns a view of the portion of this set whose elements are * strictly less than toElement. The returned set is * backed by this set, so changes in the returned set are * reflected in this set, and vice-versa. The returned set * supports all optional set operations that this set supports. * *

The returned set will throw an IllegalArgumentException * on an attempt to insert an element outside its range. * * @param toElement high endpoint (exclusive) of the returned set * @return a view of the portion of this set whose elements are strictly * less than toElement * @throws ClassCastException if toElement is not compatible * with this set's comparator (or, if the set has no comparator, * if toElement does not implement {@link Comparable}). * Implementations may, but are not required to, throw this * exception if toElement cannot be compared to elements * currently in the set. * @throws NullPointerException if toElement is null and * this set does not permit null elements * @throws IllegalArgumentException if this set itself has a * restricted range, and toElement lies outside the * bounds of the range */ SortedSet headSet(E toElement); /** * Returns a view of the portion of this set whose elements are * greater than or equal to fromElement. The returned * set is backed by this set, so changes in the returned set are * reflected in this set, and vice-versa. The returned set * supports all optional set operations that this set supports. * *

The returned set will throw an IllegalArgumentException * on an attempt to insert an element outside its range. * * @param fromElement low endpoint (inclusive) of the returned set * @return a view of the portion of this set whose elements are greater * than or equal to fromElement * @throws ClassCastException if fromElement is not compatible * with this set's comparator (or, if the set has no comparator, * if fromElement does not implement {@link Comparable}). * Implementations may, but are not required to, throw this * exception if fromElement cannot be compared to elements * currently in the set. * @throws NullPointerException if fromElement is null * and this set does not permit null elements * @throws IllegalArgumentException if this set itself has a * restricted range, and fromElement lies outside the * bounds of the range */ SortedSet tailSet(E fromElement); /** * Returns the first (lowest) element currently in this set. * * @return the first (lowest) element currently in this set * @throws NoSuchElementException if this set is empty */ E first(); /** * Returns the last (highest) element currently in this set. * * @return the last (highest) element currently in this set * @throws NoSuchElementException if this set is empty */ E last(); /** * Creates a {@code Spliterator} over the elements in this sorted set. * *

The {@code Spliterator} reports {@link Spliterator#DISTINCT}, * {@link Spliterator#SORTED} and {@link Spliterator#ORDERED}. * Implementations should document the reporting of additional * characteristic values. * *

The spliterator's comparator (see * {@link java.util.Spliterator#getComparator()}) must be {@code null} if * the sorted set's comparator (see {@link #comparator()}) is {@code null}. * Otherwise, the spliterator's comparator must be the same as or impose the * same total ordering as the sorted set's comparator. * * @implSpec * The default implementation creates a * late-binding spliterator * from the sorted set's {@code Iterator}. The spliterator inherits the * fail-fast properties of the set's iterator. The * spliterator's comparator is the same as the sorted set's comparator. *

* The created {@code Spliterator} additionally reports * {@link Spliterator#SIZED}. * * @implNote * The created {@code Spliterator} additionally reports * {@link Spliterator#SUBSIZED}. * * @return a {@code Spliterator} over the elements in this sorted set * @since 1.8 */ @Override default Spliterator spliterator() { return new Spliterators.IteratorSpliterator( this, Spliterator.DISTINCT | Spliterator.SORTED | Spliterator.ORDERED) { @Override public Comparator getComparator() { return SortedSet.this.comparator(); } }; } }