E
 the type of elements maintained by this setpublic interface SortedSet<E>
extends java.util.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.
Modifier and Type  Method and Description 

java.util.Comparator<? super E> 
comparator()
Returns the comparator used to order the elements in this set,
or null 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 than toElement.

E 
last()
Returns the last (highest) element currently in this set.

SortedSet<E> 
subSet(E fromElement,
E toElement)
Returns a view of the portion of this set whose elements range
from fromElement, inclusive, to toElement,
exclusive.

SortedSet<E> 
tailSet(E fromElement)
Returns a view of the portion of this set whose elements are
greater than or equal to fromElement.

java.util.Comparator<? super E> comparator()
SortedSet<E> subSet(E fromElement, E toElement)
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
fromElement
 low endpoint (inclusive) of the returned settoElement
 high endpoint (exclusive) of the returned setjava.lang.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.java.lang.NullPointerException
 if fromElement or
toElement is null and this set does not permit null
elementsjava.lang.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 rangeSortedSet<E> headSet(E toElement)
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
toElement
 high endpoint (exclusive) of the returned setjava.lang.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.java.lang.NullPointerException
 if toElement is null and
this set does not permit null elementsjava.lang.IllegalArgumentException
 if this set itself has a
restricted range, and toElement lies outside the
bounds of the rangeSortedSet<E> tailSet(E fromElement)
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
fromElement
 low endpoint (inclusive) of the returned setjava.lang.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.java.lang.NullPointerException
 if fromElement is null
and this set does not permit null elementsjava.lang.IllegalArgumentException
 if this set itself has a
restricted range, and fromElement lies outside the
bounds of the rangeE first()
NoSuchElementException
 if this set is emptyE last()
NoSuchElementException
 if this set is empty