NavigableSet
public
interface
NavigableSet
implements
SortedSet<E>
java.util.NavigableSet<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
.
Summary
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 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 |
default
E
|
removeFirst()
Removes and returns the first element of this collection (optional operation). |
default
E
|
removeLast()
Removes and returns the last element of this collection (optional operation). |
default
NavigableSet<E>
|
reversed()
Returns a reverse-ordered view of this collection.
This method is equivalent to |
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 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 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 | |
---|---|
Public methods
ceiling
public abstract 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 |
descendingIterator
public abstract 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 |
descendingSet
public abstract 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 |
floor
public abstract 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 |
headSet
public 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 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 |
headSet
public abstract 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 |
higher
public abstract 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
public abstract 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 |
lower
public abstract 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 |
pollFirst
public abstract 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 |
pollLast
public abstract 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 |
removeFirst
public E removeFirst ()
Removes and returns the first element of this collection (optional operation).
Implementation Requirements:
- If this set is not empty, the implementation in this interface returns the result of calling
the
pollFirst
method. Otherwise, it throwsNoSuchElementException
.
Returns | |
---|---|
E |
the removed element |
Throws | |
---|---|
NoSuchElementException |
|
UnsupportedOperationException |
removeLast
public E removeLast ()
Removes and returns the last element of this collection (optional operation).
Implementation Requirements:
- If this set is not empty, the implementation in this interface returns the result of calling
the
pollLast
method. Otherwise, it throwsNoSuchElementException
.
Returns | |
---|---|
E |
the removed element |
Throws | |
---|---|
NoSuchElementException |
|
UnsupportedOperationException |
reversed
public NavigableSet<E> reversed ()
Returns a reverse-ordered view of this collection. The encounter order of elements in the returned view is the inverse of the encounter order of elements in this collection. The reverse ordering affects all order-sensitive operations, including those on the view collections of the returned view. If the collection implementation permits modifications to this view, the modifications "write through" to the underlying collection. Changes to the underlying collection might or might not be visible in this reversed view, depending upon the implementation.
This method is equivalent to descendingSet
.
Implementation Requirements:
- The implementation in this interface returns the result of calling the
descendingSet
method.
Returns | |
---|---|
NavigableSet<E> |
a reverse-ordered view of this collection, as a NavigableSet |
subSet
public 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
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. |
subSet
public 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. (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 |
tailSet
public abstract 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 |
tailSet
public 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 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 |