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package java.util;
A Set
that further provides a total ordering on its elements. The elements are ordered using their natural
ordering, or by a 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 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.
Author: Josh Bloch Type parameters: - <E> – the type of elements maintained by this set
See Also: Since: 1.2
/**
* 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
* @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 null if this set uses the
natural ordering of its elements. Returns: the comparator used to order the elements in this set,
or null if this set uses the natural ordering
of its elements
/**
* 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 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.
Params: - fromElement – low endpoint (inclusive) of the returned set
- toElement – high endpoint (exclusive) of the returned set
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.
- NullPointerException – if fromElement or
toElement is null and this set does not permit null
elements
- 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
Returns: a view of the portion of this set whose elements range from
fromElement, inclusive, to toElement, exclusive
/**
* 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 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.
Params: - toElement – high endpoint (exclusive) of the returned set
Throws: - ClassCastException – if toElement is not compatible
with this set's comparator (or, if the set has no comparator,
if toElement does not implement
Comparable
). Implementations may, but are not required to, throw this exception if toElement cannot be compared to elements
currently in the set. - NullPointerException – if toElement is null and
this set does not permit null elements
- IllegalArgumentException – if this set itself has a
restricted range, and toElement lies outside the
bounds of the range
Returns: a view of the portion of this set whose elements are strictly
less than 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 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.
Params: - fromElement – low endpoint (inclusive) of the returned set
Throws: - ClassCastException – if fromElement is not compatible
with this set's comparator (or, if the set has no comparator,
if fromElement does not implement
Comparable
). Implementations may, but are not required to, throw this exception if fromElement cannot be compared to elements
currently in the set. - NullPointerException – if fromElement is null
and this set does not permit null elements
- IllegalArgumentException – if this set itself has a
restricted range, and fromElement lies outside the
bounds of the range
Returns: a view of the portion of this set whose elements are greater
than or equal to fromElement
/**
* 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.
Throws: - NoSuchElementException – if this set is empty
Returns: the first (lowest) element currently in this set
/**
* 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.
Throws: - NoSuchElementException – if this set is empty
Returns: the last (highest) element currently in this set
/**
* 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 Spliterator
over the elements in this sorted set. The Spliterator
reports Spliterator.DISTINCT
, Spliterator.SORTED
and Spliterator.ORDERED
. Implementations should document the reporting of additional characteristic values.
The spliterator's comparator (see Spliterator.getComparator()
) must be null
if the sorted set's comparator (see comparator()
) is null
. Otherwise, the spliterator's comparator must be the same as or impose the same total ordering as the sorted set's comparator.
Implementation Requirements:
The default implementation creates a
late-binding spliterator from the sorted set's 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 Spliterator
additionally reports Spliterator.SIZED
.
Implementation Note: The created Spliterator
additionally reports Spliterator.SUBSIZED
. Returns: a Spliterator
over the elements in this sorted set Since: 1.8
/**
* Creates a {@code Spliterator} over the elements in this sorted set.
*
* <p>The {@code Spliterator} reports {@link Spliterator#DISTINCT},
* {@link Spliterator#SORTED} and {@link Spliterator#ORDERED}.
* Implementations should document the reporting of additional
* characteristic values.
*
* <p>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
* <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator
* from the sorted set's {@code Iterator}. The spliterator inherits the
* <em>fail-fast</em> properties of the set's iterator. The
* spliterator's comparator is the same as the sorted set's comparator.
* <p>
* 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<E> spliterator() {
return new Spliterators.IteratorSpliterator<E>(
this, Spliterator.DISTINCT | Spliterator.SORTED | Spliterator.ORDERED) {
@Override
public Comparator<? super E> getComparator() {
return SortedSet.this.comparator();
}
};
}
}