 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>
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 welldefined even if its
ordering is inconsistent with equals; it just fails to obey the general
contract of the Set
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 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 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
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.
 Since:
 1.2
 See Also:
Set
,TreeSet
,SortedMap
,Collection
,Comparable
,Comparator
,ClassCastException

Method Summary
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, toArray

Method Details

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
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
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
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
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
