
 Type Parameters:
E
 the type of elements maintained by this set
 All Superinterfaces:
Collection<E>
,Iterable<E>
,Set<E>
 All Known Subinterfaces:
NavigableSet<E>
 All Known Implementing Classes:
ConcurrentSkipListSet
,TreeSet
public interface SortedSet<E> extends Set<E>
ASet
that further provides a total ordering on its elements. The elements are ordered using their natural ordering, or by aComparator
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 ofSortedMap
.)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)
(orcomparator.compare(e1, e2)
) must not throw aClassCastException
for any elementse1
ande2
in the sorted set. Attempts to violate this restriction will cause the offending method or constructor invocation to throw aClassCastException
.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 theComparable
interface orComparator
interface for a precise definition of consistent with equals.) This is so because theSet
interface is defined in terms of theequals
operation, but a sorted set performs all element comparisons using itscompareTo
(orcompare
) 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 welldefined even if its ordering is inconsistent with equals; it just fails to obey the general contract of theSet
interface.All generalpurpose 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 typeCollection
, 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 typeSortedSet
, 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 halfopen, 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
tosuccessor(highEndpoint)
. For example, suppose thats
is a sorted set of strings. The following idiom obtains a view containing all of the strings ins
fromlow
tohigh
, 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 ins
fromlow
tohigh
, exclusive:SortedSet<String> sub = s.subSet(low+"\0", high);
This interface is a member of the Java Collections Framework.
 Since:
 1.2
 See Also:
Set
,TreeSet
,SortedMap
,Collection
,Comparable
,Comparator
,ClassCastException


Method Summary
All Methods Instance Methods Abstract Methods Default Methods Modifier and Type Method Description Comparator<? super E>
comparator()
Returns the comparator used to order the elements in this set, ornull
if this set uses the natural ordering of its elements.E
first()
Returns the first (lowest) element currently in this set.SortedSet<E>
headSet(E toElement)
Returns a view of the portion of this set whose elements are strictly less thantoElement
.E
last()
Returns the last (highest) element currently in this set.default Spliterator<E>
spliterator()
Creates aSpliterator
over the elements in this sorted set.SortedSet<E>
subSet(E fromElement, E toElement)
Returns a view of the portion of this set whose elements range fromfromElement
, inclusive, totoElement
, exclusive.SortedSet<E>
tailSet(E fromElement)
Returns a view of the portion of this set whose elements are greater than or equal tofromElement
.
Methods declared in interface java.util.Collection
parallelStream, removeIf, stream




Method Detail

comparator
Comparator<? super E> comparator()
Returns the comparator used to order the elements in this set, ornull
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

subSet
SortedSet<E> subSet(E fromElement, E toElement)
Returns a view of the portion of this set whose elements range fromfromElement
, inclusive, totoElement
, exclusive. (IffromElement
andtoElement
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 viceversa. 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. Parameters:
fromElement
 low endpoint (inclusive) of the returned settoElement
 high endpoint (exclusive) of the returned set Returns:
 a view of the portion of this set whose elements range from
fromElement
, inclusive, totoElement
, exclusive  Throws:
ClassCastException
 iffromElement
andtoElement
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 iffromElement
ortoElement
cannot be compared to elements currently in the set.NullPointerException
 iffromElement
ortoElement
is null and this set does not permit null elementsIllegalArgumentException
 iffromElement
is greater thantoElement
; or if this set itself has a restricted range, andfromElement
ortoElement
lies outside the bounds of the range

headSet
SortedSet<E> headSet(E toElement)
Returns a view of the portion of this set whose elements are strictly less thantoElement
. The returned set is backed by this set, so changes in the returned set are reflected in this set, and viceversa. 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. Parameters:
toElement
 high endpoint (exclusive) of the returned set Returns:
 a view of the portion of this set whose elements are strictly
less than
toElement
 Throws:
ClassCastException
 iftoElement
is not compatible with this set's comparator (or, if the set has no comparator, iftoElement
does not implementComparable
). Implementations may, but are not required to, throw this exception iftoElement
cannot be compared to elements currently in the set.NullPointerException
 iftoElement
is null and this set does not permit null elementsIllegalArgumentException
 if this set itself has a restricted range, andtoElement
lies outside the bounds of the range

tailSet
SortedSet<E> tailSet(E fromElement)
Returns a view of the portion of this set whose elements are greater than or equal tofromElement
. The returned set is backed by this set, so changes in the returned set are reflected in this set, and viceversa. 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. Parameters:
fromElement
 low endpoint (inclusive) of the returned set Returns:
 a view of the portion of this set whose elements are greater
than or equal to
fromElement
 Throws:
ClassCastException
 iffromElement
is not compatible with this set's comparator (or, if the set has no comparator, iffromElement
does not implementComparable
). Implementations may, but are not required to, throw this exception iffromElement
cannot be compared to elements currently in the set.NullPointerException
 iffromElement
is null and this set does not permit null elementsIllegalArgumentException
 if this set itself has a restricted range, andfromElement
lies outside the bounds of the range

first
E first()
Returns the first (lowest) element currently in this set. Returns:
 the first (lowest) element currently in this set
 Throws:
NoSuchElementException
 if this set is empty

last
E last()
Returns the last (highest) element currently in this set. Returns:
 the last (highest) element currently in this set
 Throws:
NoSuchElementException
 if this set is empty

spliterator
default Spliterator<E> spliterator()
Creates aSpliterator
over the elements in this sorted set.The
Spliterator
reportsSpliterator.DISTINCT
,Spliterator.SORTED
andSpliterator.ORDERED
. Implementations should document the reporting of additional characteristic values.The spliterator's comparator (see
Spliterator.getComparator()
) must benull
if the sorted set's comparator (seecomparator()
) isnull
. Otherwise, the spliterator's comparator must be the same as or impose the same total ordering as the sorted set's comparator. Specified by:
spliterator
in interfaceCollection<E>
 Specified by:
spliterator
in interfaceIterable<E>
 Specified by:
spliterator
in interfaceSet<E>
 Implementation Requirements:
 The default implementation creates a
latebinding spliterator
from the sorted set's
Iterator
. The spliterator inherits the failfast properties of the set's iterator. The spliterator's comparator is the same as the sorted set's comparator.The created
Spliterator
additionally reportsSpliterator.SIZED
.  Implementation Note:
 The created
Spliterator
additionally reportsSpliterator.SUBSIZED
.  Returns:
 a
Spliterator
over the elements in this sorted set  Since:
 1.8

