Interface java.util.SortedSet
- Implementing Classes:
- TreeSet
- public interface SortedSet
- extends Set
A Set that further guarantees that its iterator will traverse the Set in
ascending element order, sorted according to the natural ordering of
its elements (see Comparable), or by a Comparator provided at SortedSet
creation time. Several additional operations are provided to take
advantage of the ordering. (This interface is the Set analogue of
SortedMap.)
All elements inserted into an SortedSet 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 typeMismatchException for any
elements e1 and e2 in the SortedSet. Attempts to violate this restriction
will cause the offending method or constructor invocation to throw a
ClassCastException.
Note that the ordering maintained by a SortedSet (whether or not an
explicit Comparator is provided) must be total if the SortedSet is
to correctly implement the Set interface. (See Comparable or Comparator
for a definition of total ordering.) This is so because the Set
interface is defined in terms of the equals operation, but a SortedSet
performs all key comparisons using its compareTo (or compare) method, so
two keys that are deemed equal by this method are, from the standpoint of
the SortedSet, equal. The only JDK class whose natural ordering does not
satisfy this constraint is BigDecimal.
All general-purpose SortedSet implementation classes should provide four
"standard" constructors: 1) A void (no arguments) constructor, which
creates an empty SortedSet sorted according to the natural order
of its elements. 2) A constructor with a single argument of
type Comparator, which creates an empty SortedSet sorted according to the
specified Comparator. 3) A constructor with a single argument of type
Collection, which creates a new Set with the same elements as its argument,
sorted according to the elements' natural ordering. 4) A constructor
with a single argument of type SortedSet, which creates a new SortedSet
with the same elements and the same ordering as the input SortedSet.
There is no way to enforce this recommendation (as interfaces cannot
contain constructors) but the JDK implementation (TreeSet) complies.
- Since:
- JDK1.2
- See Also:
- Set, TreeSet, SortedMap, Collection, ClassCastException
Method Summary
|
Comparator
|
comparator()
Returns the Comparator associated with this SortedSet, or null
if it uses its elements' natural ordering.
|
Object
|
first()
Returns the first (lowest) element currently in this SortedSet.
|
SortedSet
|
headSet(Object toElement)
Returns a view of the portion of this SortedSet whose elements are
strictly less than toElement.
|
Object
|
last()
Returns the last (highest) element currently in this SortedSet.
|
SortedSet
|
subSet(Object fromElement,
Object toElement)
Returns a view of the portion of this SortedSet whose elements range
from fromElement, inclusive, to toElement, exclusive.
|
SortedSet
|
tailSet(Object fromElement)
Returns a view of the portion of this SortedSet whose elements are
greater than or equal to fromElement.
|
comparator
public Comparator comparator()
- Returns the Comparator associated with this SortedSet, or null
if it uses its elements' natural ordering.
- Returns:
- the Comparator associated with this SortedSet, or null
if it uses its elements' natural ordering.
subSet
public SortedSet subSet(Object fromElement,
Object toElement)
- Returns a view of the portion of this SortedSet whose elements range
from fromElement, inclusive, to toElement, exclusive. The returned
SortedSet is backed by this SortedSet, so changes in the returned
SortedSet are reflected in this SortedSet, and vice-versa. The
returned Set supports all optional Set operations.
The Set returned by this method will throw an IllegalArgumentException
if the user attempts to insert a element outside the specified range.
- Parameters:
fromElement
- low endpoint (inclusive) of the subSet.
toElement
- high endpoint (exclusive) of the subSet.
- Returns:
- a view of the specified range within this SortedSet.
- Throws:
- ClassCastException - fromElement or toElement cannot be
compared with the elements currently in the SortedSet.
- NullPointerException - fromElement or toElement is null and
this SortedSet does not tolerate null elements.
- IllegalArgumentException - fromElement is greater than
toElement.
headSet
public SortedSet headSet(Object toElement)
- Returns a view of the portion of this SortedSet whose elements are
strictly less than toElement. The returned SortedSet is backed by this
SortedSet, so changes in the returned SortedSet are reflected in this
SortedSet, and vice-versa. The returned Set supports all optional Set
operations.
The Set returned by this method will throw an IllegalArgumentException
if the user attempts to insert a element outside the specified range.
- Parameters:
toElement
- high endpoint (exclusive) of the headSet.
- Returns:
- a view of the specified initial range of this SortedSet.
- Throws:
- ClassCastException - toElement cannot be compared with the
elements currently in the SortedSet.
- NullPointerException - toElement is null and this SortedSet
does not tolerate null elements.
tailSet
public SortedSet tailSet(Object fromElement)
- Returns a view of the portion of this SortedSet whose elements are
greater than or equal to fromElement. The returned SortedSet is
backed by this SortedSet, so changes in the returned SortedSet are
reflected in this SortedSet, and vice-versa. The returned Set
supports all optional Set operations.
The Set returned by this method will throw an IllegalArgumentException
if the user attempts to insert a element outside the specified range.
- Parameters:
toElement
- high endpoint (exclusive) of the tailSet.
- Returns:
- a view of the specified final range of this SortedSet.
- Throws:
- ClassCastException - toElement cannot be compared with the
elements currently in the SortedSet.
- NullPointerException - fromElement is null and this SortedSet
does not tolerate null elements.
first
public Object first()
- Returns the first (lowest) element currently in this SortedSet.
- Returns:
- the first (lowest) element currently in this SortedSet.
- Throws:
- NoSuchElementException - Set is empty.
last
public Object last()
- Returns the last (highest) element currently in this SortedSet.
- Returns:
- the last (highest) element currently in this SortedSet.
- Throws:
- NoSuchElementException - Set is empty.
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