/*
* @(#)SortedSet.java 1.32 06/04/21
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util;
/**
* A {@link Set} that further provides a <i>total ordering</i> 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}.)
*
* <p>All elements inserted into a sorted set must implement the <tt>Comparable</tt>
* interface (or be accepted by the specified comparator). Furthermore, all
* such elements must be <i>mutually comparable</i>: <tt>e1.compareTo(e2)</tt>
* (or <tt>comparator.compare(e1, e2)</tt>) must not throw a
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and <tt>e2</tt> in
* the sorted set. Attempts to violate this restriction will cause the
* offending method or constructor invocation to throw a
* <tt>ClassCastException</tt>.
*
* <p>Note that the ordering maintained by a sorted set (whether or not an
* explicit comparator is provided) must be <i>consistent with equals</i> if
* the sorted set is to correctly implement the <tt>Set</tt> interface. (See
* the <tt>Comparable</tt> interface or <tt>Comparator</tt> interface for a
* precise definition of <i>consistent with equals</i>.) This is so because
* the <tt>Set</tt> interface is defined in terms of the <tt>equals</tt>
* operation, but a sorted set performs all element comparisons using its
* <tt>compareTo</tt> (or <tt>compare</tt>) 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 <i>is</i> well-defined even if its
* ordering is inconsistent with equals; it just fails to obey the general
* contract of the <tt>Set</tt> interface.
*
* <p>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 <tt>Comparator</tt>, which creates an empty
* sorted set sorted according to the specified comparator. 3) A
* constructor with a single argument of type <tt>Collection</tt>,
* 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 <tt>SortedSet</tt>,
* 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.
*
* <p>Note: several methods return subsets with restricted ranges.
* Such ranges are <i>half-open</i>, that is, they include their low
* endpoint but not their high endpoint (where applicable).
* If you need a <i>closed range</i> (which includes both endpoints), and
* the element type allows for calculation of the successor of a given
* value, merely request the subrange from <tt>lowEndpoint</tt> to
* <tt>successor(highEndpoint)</tt>. For example, suppose that <tt>s</tt>
* is a sorted set of strings. The following idiom obtains a view
* containing all of the strings in <tt>s</tt> from <tt>low</tt> to
* <tt>high</tt>, inclusive:<pre>
* SortedSet<String> sub = s.subSet(low, high+"\0");</pre>
*
* A similar technique can be used to generate an <i>open range</i> (which
* contains neither endpoint). The following idiom obtains a view
* containing all of the Strings in <tt>s</tt> from <tt>low</tt> to
* <tt>high</tt>, exclusive:<pre>
* SortedSet<String> sub = s.subSet(low+"\0", high);</pre>
*
* <p>This interface is a member of the
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
* Java Collections Framework</a>.
*
* @param <E> the type of elements maintained by this set
*
* @author Josh Bloch
* @version 1.32, 04/21/06
* @see Set
* @see TreeSet
* @see SortedMap
* @see Collection
* @see Comparable
* @see Comparator
* @see ClassCastException
* @since 1.2
*/
public interface SortedSet<E> extends Set<E> {
/**
* Returns the comparator used to order the elements in this set,
* or <tt>null</tt> if this set uses the {@linkplain Comparable
* natural ordering} of its elements.
*
* @return the comparator used to order the elements in this set,
* or <tt>null</tt> if this set uses the natural ordering
* of its elements
*/
Comparator<? super E> comparator();
/**
* 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 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.
*
* <p>The returned set will throw an <tt>IllegalArgumentException</tt>
* 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
* <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). Implementations may, but are not required
* to, throw this exception if <tt>fromElement</tt> or
* <tt>toElement</tt> cannot be compared to elements currently in
* the set.
* @throws NullPointerException if <tt>fromElement</tt> or
* <tt>toElement</tt> is null and this set does not permit null
* elements
* @throws IllegalArgumentException if <tt>fromElement</tt> is
* greater than <tt>toElement</tt>; or if this set itself
* has a restricted range, and <tt>fromElement</tt> or
* <tt>toElement</tt> lies outside the bounds of the range
*/
SortedSet<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 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.
*
* <p>The returned set will throw an <tt>IllegalArgumentException</tt>
* 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 <tt>toElement</tt>
* @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 {@link Comparable}).
* Implementations may, but are not required to, throw this
* exception if <tt>toElement</tt> cannot be compared to elements
* currently in the set.
* @throws NullPointerException if <tt>toElement</tt> is null and
* this set does not permit null elements
* @throws IllegalArgumentException if this set itself has a
* restricted range, and <tt>toElement</tt> lies outside the
* bounds of the range
*/
SortedSet<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
* 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.
*
* <p>The returned set will throw an <tt>IllegalArgumentException</tt>
* 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 <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 {@link Comparable}).
* Implementations may, but are not required to, throw this
* exception if <tt>fromElement</tt> cannot be compared to elements
* currently in the set.
* @throws NullPointerException if <tt>fromElement</tt> is null
* and this set does not permit null elements
* @throws IllegalArgumentException if this set itself has a
* restricted range, and <tt>fromElement</tt> lies outside the
* bounds of the range
*/
SortedSet<E> 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();
}
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