public
interface
NavigableSet
implements
SortedSet<E>
java.util.NavigableSet<E> |
Known Indirect Subclasses
ConcurrentSkipListSet<E>,
TreeSet<E>
|
A SortedSet
extended with navigation methods reporting
closest matches for given search targets. Methods lower(E)
,
floor(E)
, ceiling(E)
, and higher(E)
return elements
respectively less than, less than or equal, greater than or equal,
and greater than a given element, returning null
if there
is no such element.
A NavigableSet
may be accessed and traversed in either
ascending or descending order. The descendingSet()
method
returns a view of the set with the senses of all relational and
directional methods inverted. The performance of ascending
operations and views is likely to be faster than that of descending
ones. This interface additionally defines methods pollFirst()
and pollLast()
that return and remove the lowest
and highest element, if one exists, else returning null
.
Methods
subSet(E, boolean, E, boolean)
,
headSet(E, boolean)
, and
tailSet(E, boolean)
differ from the like-named SortedSet
methods in accepting
additional arguments describing whether lower and upper bounds are
inclusive versus exclusive. Subsets of any NavigableSet
must implement the NavigableSet
interface.
The return values of navigation methods may be ambiguous in
implementations that permit null
elements. However, even
in this case the result can be disambiguated by checking
contains(null)
. To avoid such issues, implementations of
this interface are encouraged to not permit insertion of
null
elements. (Note that sorted sets of Comparable
elements intrinsically do not permit null
.)
Methods
subSet(E, E)
,
headSet(E)
, and
tailSet(E)
are specified to return SortedSet
to allow existing
implementations of SortedSet
to be compatibly retrofitted to
implement NavigableSet
, but extensions and implementations
of this interface are encouraged to override these methods to return
NavigableSet
.
Public methods | |
---|---|
abstract
E
|
ceiling(E e)
Returns the least element in this set greater than or equal to
the given element, or |
abstract
Iterator<E>
|
descendingIterator()
Returns an iterator over the elements in this set, in descending order. |
abstract
NavigableSet<E>
|
descendingSet()
Returns a reverse order view of the elements contained in this set. |
abstract
E
|
floor(E e)
Returns the greatest element in this set less than or equal to
the given element, or |
abstract
NavigableSet<E>
|
headSet(E toElement, boolean inclusive)
Returns a view of the portion of this set whose elements are less than
(or equal to, if |
abstract
SortedSet<E>
|
headSet(E toElement)
Returns a view of the portion of this set whose elements are strictly less than toElement. Equivalent to |
abstract
E
|
higher(E e)
Returns the least element in this set strictly greater than the
given element, or |
abstract
Iterator<E>
|
iterator()
Returns an iterator over the elements in this set, in ascending order. |
abstract
E
|
lower(E e)
Returns the greatest element in this set strictly less than the
given element, or |
abstract
E
|
pollFirst()
Retrieves and removes the first (lowest) element,
or returns |
abstract
E
|
pollLast()
Retrieves and removes the last (highest) element,
or returns |
abstract
NavigableSet<E>
|
subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
Returns a view of the portion of this set whose elements range from
|
abstract
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. Equivalent to |
abstract
SortedSet<E>
|
tailSet(E fromElement)
Returns a view of the portion of this set whose elements are greater than or equal to fromElement. Equivalent to |
abstract
NavigableSet<E>
|
tailSet(E fromElement, boolean inclusive)
Returns a view of the portion of this set whose elements are greater
than (or equal to, if |
Inherited methods | |
---|---|
From
interface
java.util.SortedSet
| |
From
interface
java.util.Set
| |
From
interface
java.util.Collection
| |
From
interface
java.lang.Iterable
|
E ceiling (E e)
Returns the least element in this set greater than or equal to
the given element, or null
if there is no such element.
Parameters | |
---|---|
e |
E :
the value to match |
Returns | |
---|---|
E |
the least element greater than or equal to e ,
or null if there is no such element |
Throws | |
---|---|
ClassCastException |
if the specified element cannot be compared with the elements currently in the set |
NullPointerException |
if the specified element is null and this set does not permit null elements |
Iterator<E> descendingIterator ()
Returns an iterator over the elements in this set, in descending order.
Equivalent in effect to descendingSet().iterator()
.
Returns | |
---|---|
Iterator<E> |
an iterator over the elements in this set, in descending order |
NavigableSet<E> descendingSet ()
Returns a reverse order view of the elements contained in this set.
The descending set is backed by this set, so changes to the set are
reflected in the descending set, and vice-versa. If either set is
modified while an iteration over either set is in progress (except
through the iterator's own remove
operation), the results of
the iteration are undefined.
The returned set has an ordering equivalent to
Collections.reverseOrder
(comparator())
.
The expression s.descendingSet().descendingSet()
returns a
view of s
essentially equivalent to s
.
Returns | |
---|---|
NavigableSet<E> |
a reverse order view of this set |
E floor (E e)
Returns the greatest element in this set less than or equal to
the given element, or null
if there is no such element.
Parameters | |
---|---|
e |
E :
the value to match |
Returns | |
---|---|
E |
the greatest element less than or equal to e ,
or null if there is no such element |
Throws | |
---|---|
ClassCastException |
if the specified element cannot be compared with the elements currently in the set |
NullPointerException |
if the specified element is null and this set does not permit null elements |
NavigableSet<E> headSet (E toElement, boolean inclusive)
Returns a view of the portion of this set whose elements are less than
(or equal to, if inclusive
is true) toElement
. The
returned set is backed by this set, so changes in the returned set are
reflected in this set, and vice-versa. 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 |
E :
high endpoint of the returned set |
inclusive |
boolean :
true if the high endpoint
is to be included in the returned view |
Returns | |
---|---|
NavigableSet<E> |
a view of the portion of this set whose elements are less than
(or equal to, if inclusive is true) toElement |
Throws | |
---|---|
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. |
NullPointerException |
if toElement is null and
this set does not permit null elements |
IllegalArgumentException |
if this set itself has a
restricted range, and toElement lies outside the
bounds of the range
|
SortedSet<E> headSet (E toElement)
Returns a view of the portion of this set whose elements are strictly less than toElement. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. 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.
Equivalent to headSet(toElement, false)
.
Parameters | |
---|---|
toElement |
E :
high endpoint (exclusive) of the returned set |
Returns | |
---|---|
SortedSet<E> |
a view of the portion of this set whose elements are strictly less than toElement |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
|
IllegalArgumentException |
E higher (E e)
Returns the least element in this set strictly greater than the
given element, or null
if there is no such element.
Parameters | |
---|---|
e |
E :
the value to match |
Returns | |
---|---|
E |
the least element greater than e ,
or null if there is no such element |
Throws | |
---|---|
ClassCastException |
if the specified element cannot be compared with the elements currently in the set |
NullPointerException |
if the specified element is null and this set does not permit null elements |
Iterator<E> iterator ()
Returns an iterator over the elements in this set, in ascending order.
Returns | |
---|---|
Iterator<E> |
an iterator over the elements in this set, in ascending order |
E lower (E e)
Returns the greatest element in this set strictly less than the
given element, or null
if there is no such element.
Parameters | |
---|---|
e |
E :
the value to match |
Returns | |
---|---|
E |
the greatest element less than e ,
or null if there is no such element |
Throws | |
---|---|
ClassCastException |
if the specified element cannot be compared with the elements currently in the set |
NullPointerException |
if the specified element is null and this set does not permit null elements |
E pollFirst ()
Retrieves and removes the first (lowest) element,
or returns null
if this set is empty.
Returns | |
---|---|
E |
the first element, or null if this set is empty
|
E pollLast ()
Retrieves and removes the last (highest) element,
or returns null
if this set is empty.
Returns | |
---|---|
E |
the last element, or null if this set is empty
|
NavigableSet<E> subSet (E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
Returns a view of the portion of this set whose elements range from
fromElement
to toElement
. If fromElement
and
toElement
are equal, the returned set is empty unless fromInclusive
and toInclusive
are both true. The returned set
is backed by this set, so changes in the returned set are reflected in
this set, and vice-versa. 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 |
E :
low endpoint of the returned set |
fromInclusive |
boolean :
true if the low endpoint
is to be included in the returned view |
toElement |
E :
high endpoint of the returned set |
toInclusive |
boolean :
true if the high endpoint
is to be included in the returned view |
Returns | |
---|---|
NavigableSet<E> |
a view of the portion of this set whose elements range from
fromElement , inclusive, to toElement , exclusive |
Throws | |
---|---|
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. |
NullPointerException |
if fromElement or
toElement is null and this set does
not permit null elements |
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 range.
|
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. (If fromElement and toElement 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 vice-versa. 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.
Equivalent to subSet(fromElement, true, toElement, false)
.
Parameters | |
---|---|
fromElement |
E :
low endpoint (inclusive) of the returned set |
toElement |
E :
high endpoint (exclusive) of the returned set |
Returns | |
---|---|
SortedSet<E> |
a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
|
IllegalArgumentException |
SortedSet<E> tailSet (E fromElement)
Returns a view of the portion of this set whose elements are greater than or equal to fromElement. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. 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.
Equivalent to tailSet(fromElement, true)
.
Parameters | |
---|---|
fromElement |
E :
low endpoint (inclusive) of the returned set |
Returns | |
---|---|
SortedSet<E> |
a view of the portion of this set whose elements are greater than or equal to fromElement |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
|
IllegalArgumentException |
NavigableSet<E> tailSet (E fromElement, boolean inclusive)
Returns a view of the portion of this set whose elements are greater
than (or equal to, if inclusive
is true) fromElement
.
The returned set is backed by this set, so changes in the returned set
are reflected in this set, and vice-versa. 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 |
E :
low endpoint of the returned set |
inclusive |
boolean :
true if the low endpoint
is to be included in the returned view |
Returns | |
---|---|
NavigableSet<E> |
a view of the portion of this set whose elements are greater
than or equal to fromElement |
Throws | |
---|---|
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. |
NullPointerException |
if fromElement is null
and this set does not permit null elements |
IllegalArgumentException |
if this set itself has a
restricted range, and fromElement lies outside the
bounds of the range
|