public interface SortedSet<E>
A
Set
that further provides a
A set that further guarantees that its iterator will traverse the set in ascending element order, sorted according to the
total
natural
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.
of its elements (see Comparable), or by a Comparator provided at sorted set creation time.
Several additional operations are provided to take advantage of the ordering. (This interface is the set analogue of
SortedMap
.)
SortedMap.)
All elements inserted into
a
an
sorted set must implement the
Comparable
interface (or be accepted by the specified
comparator).
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
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
half-open
natural order
, 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
of its elements. 2) A constructor with a single argument of type
lowEndpoint
Comparator
to
, which creates an empty sorted set sorted according to the specified comparator. 3) A constructor with a single argument of type
successor(highEndpoint)
Collection
. For example, suppose that
, which creates a new sorted set with the same elements as its argument, sorted according to the elements' natural ordering. 4) A constructor with a single argument of type
s
SortedSet
is a sorted set of strings. The following idiom obtains a view containing all of the strings in
, 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) but the JDK implementation (the
s
TreeSet
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 .
Method Summary | |
---|---|
Comparator <? super E |
comparator
() Returns the comparator used to order the elements in |
E |
first
() Returns the first (lowest) element currently in this |
SortedSet < E |
headSet
(
E
Returns a view of the portion of this |
E |
last
() Returns the last (highest) element currently in this |
SortedSet < E |
subSet
(
E
fromElement,
E
Returns a view of the portion of this |
SortedSet < E |
tailSet
(
E
Returns a view of the portion of this |
Methods inherited from interface java.util. Set |
---|
add , addAll , clear , contains , containsAll , equals , hashCode , isEmpty , iterator , remove , removeAll , retainAll , size , toArray , toArray |
Method Detail |
---|
Comparator<? super E> comparator()
SortedSet<E> subSet(E fromElement, E toElement)
The
sorted set
returned
set
by this method
will throw an
IllegalArgumentException
on an attempt to insert an element outside its range.
if the user attempts to insert a element outside the specified range.
Note: this method always returns a
half-open range
(which includes its low endpoint but not its high endpoint). If you need a
closed range
(which includes both endpoints), and the element type allows for calculation of the successor 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 sub = s.subSet(low, high+"\0");
SortedSet sub = s.subSet(low+"\0", high);
SortedSet<E> headSet(E toElement)
The
sorted set
returned
set
by this method
will throw an
IllegalArgumentException
on an attempt to insert an element outside its range.
if the user attempts to insert a element outside the specified range.
Note: this method always returns a view that does not contain its (high) endpoint. If you need a view that does contain this endpoint, and the element type allows for calculation of the successor a given value, merely request a headSet bounded by
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
that are less than or equal to
high
:
SortedSet head = s.headSet(high+"\0");
SortedSet<E> tailSet(E fromElement)
The
sorted set
returned
set
by this method
will throw an
IllegalArgumentException
on an attempt to insert an element outside its range.
if the user attempts to insert a element outside the specified range.
Note: this method always returns a view that contains its (low) endpoint. If you need a view that does not contain this endpoint, and the element type allows for calculation of the successor a given value, merely request a tailSet bounded by
successor(lowEndpoint)
. For example, suppose that
s
is a sorted set of strings. The following idiom obtains a view containing all of the strings in
s
that are strictly greater than
low
:
SortedSet tail = s.tailSet(low+"\0");
E first()
E last()