A
SortedMap
extended with navigation methods returning the
closest matches for given search targets. Methods
lowerEntry
,
floorEntry
,
ceilingEntry
,
and
higherEntry
return
Map.Entry
objects
associated with keys respectively less than, less than or equal,
greater than or equal, and greater than a given key, returning
null
if there is no such key. Similarly, methods
lowerKey
,
floorKey
,
ceilingKey
, and
higherKey
return only the associated keys. All of these
methods are designed for locating, not traversing entries.
A
NavigableMap
may be accessed and traversed in either
ascending or descending key order. The
descendingMap
method returns a view of the map 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. Methods
subMap
,
headMap
,
and
tailMap
differ from the like-named
SortedMap
methods in accepting additional arguments describing
whether lower and upper bounds are inclusive versus exclusive.
Submaps of any
NavigableMap
must implement the
NavigableMap
interface.
This interface additionally defines methods
firstEntry
,
pollFirstEntry
,
lastEntry
, and
pollLastEntry
that return and/or remove the least and
greatest mappings, if any exist, else returning
null
.
Implementations of entry-returning methods are expected to
return
Map.Entry
pairs representing snapshots of mappings
at the time they were produced, and thus generally do
not
support the optional
Entry.setValue
method. Note however
that it is possible to change mappings in the associated map using
method
put
.
Methods
subMap(K, K)
,
headMap(K)
, and
tailMap(K)
are specified to return
SortedMap
to allow existing
implementations of
SortedMap
to be compatibly retrofitted to
implement
NavigableMap
, but extensions and implementations
of this interface are encouraged to override these methods to return
NavigableMap
. Similarly,
keySet()
can be overriden to return
NavigableSet
.
This interface is a member of the
../../../technotes/guides/collections/index.html">
Java Collections Framework.
ceilingEntry
public java.util.Map.Entry ceilingEntry(K key)
Returns a key-value mapping associated with the least key
greater than or equal to the given key, or null
if
there is no such key.
- an entry with the least key greater than or equal to
key
, or null
if there is no such key
ceilingKey
public K ceilingKey(K key)
Returns the least key greater than or equal to the given key,
or null
if there is no such key.
- the least key greater than or equal to
key
,
or null
if there is no such key
descendingKeySet
public NavigableSet descendingKeySet()
Returns a reverse order
NavigableSet
view of the keys contained in this map.
The set's iterator returns the keys in descending order.
The set is backed by the map, so changes to the map are reflected in
the set, and vice-versa. If the map is modified while an iteration
over the set is in progress (except through the iterator's own
remove
operation), the results of the iteration are undefined. The
set supports element removal, which removes the corresponding mapping
from the map, via the
Iterator.remove
,
Set.remove
,
removeAll
,
retainAll
, and
clear
operations.
It does not support the
add
or
addAll
operations.
- a reverse order navigable set view of the keys in this map
descendingMap
public NavigableMap descendingMap()
Returns a reverse order view of the mappings contained in this map.
The descending map is backed by this map, so changes to the map are
reflected in the descending map, and vice-versa. If either map is
modified while an iteration over a collection view of either map
is in progress (except through the iterator's own
remove
operation), the results of the iteration are undefined.
The returned map has an ordering equivalent to
Collections.reverseOrder
(comparator()).
The expression
m.descendingMap().descendingMap()
returns a
view of
m
essentially equivalent to
m
.
- a reverse order view of this map
firstEntry
public java.util.Map.Entry firstEntry()
Returns a key-value mapping associated with the least
key in this map, or null
if the map is empty.
- an entry with the least key,
or
null
if this map is empty
floorEntry
public java.util.Map.Entry floorEntry(K key)
Returns a key-value mapping associated with the greatest key
less than or equal to the given key, or null
if there
is no such key.
- an entry with the greatest key less than or equal to
key
, or null
if there is no such key
floorKey
public K floorKey(K key)
Returns the greatest key less than or equal to the given key,
or null
if there is no such key.
- the greatest key less than or equal to
key
,
or null
if there is no such key
headMap
public SortedMap headMap(K toKey)
Equivalent to headMap(toKey, false)
.
headMap
public NavigableMap headMap(K toKey,
boolean inclusive)
Returns a view of the portion of this map whose keys are less than (or
equal to, if
inclusive
is true)
toKey
. The returned
map is backed by this map, so changes in the returned map are reflected
in this map, and vice-versa. The returned map supports all optional
map operations that this map supports.
The returned map will throw an
IllegalArgumentException
on an attempt to insert a key outside its range.
toKey
- high endpoint of the keys in the returned mapinclusive
- true
if the high endpoint
is to be included in the returned view
- a view of the portion of this map whose keys are less than
(or equal to, if
inclusive
is true) toKey
ClassCastException
- if toKey
is not compatible
with this map's comparator (or, if the map has no comparator,
if toKey
does not implement Comparable
).
Implementations may, but are not required to, throw this
exception if toKey
cannot be compared to keys
currently in the map.NullPointerException
- if toKey
is null
and this map does not permit null keysIllegalArgumentException
- if this map itself has a
restricted range, and toKey
lies outside the
bounds of the range
higherEntry
public java.util.Map.Entry higherEntry(K key)
Returns a key-value mapping associated with the least key
strictly greater than the given key, or null
if there
is no such key.
- an entry with the least key greater than
key
,
or null
if there is no such key
higherKey
public K higherKey(K key)
Returns the least key strictly greater than the given key, or
null
if there is no such key.
- the least key greater than
key
,
or null
if there is no such key
lastEntry
public java.util.Map.Entry lastEntry()
Returns a key-value mapping associated with the greatest
key in this map, or null
if the map is empty.
- an entry with the greatest key,
or
null
if this map is empty
lowerEntry
public java.util.Map.Entry lowerEntry(K key)
Returns a key-value mapping associated with the greatest key
strictly less than the given key, or null
if there is
no such key.
- an entry with the greatest key less than
key
,
or null
if there is no such key
lowerKey
public K lowerKey(K key)
Returns the greatest key strictly less than the given key, or
null
if there is no such key.
- the greatest key less than
key
,
or null
if there is no such key
navigableKeySet
public NavigableSet navigableKeySet()
Returns a
NavigableSet
view of the keys contained in this map.
The set's iterator returns the keys in ascending order.
The set is backed by the map, so changes to the map are reflected in
the set, and vice-versa. If the map is modified while an iteration
over the set is in progress (except through the iterator's own
remove
operation), the results of the iteration are undefined. The
set supports element removal, which removes the corresponding mapping
from the map, via the
Iterator.remove
,
Set.remove
,
removeAll
,
retainAll
, and
clear
operations.
It does not support the
add
or
addAll
operations.
- a navigable set view of the keys in this map
pollFirstEntry
public java.util.Map.Entry pollFirstEntry()
Removes and returns a key-value mapping associated with
the least key in this map, or null
if the map is empty.
- the removed first entry of this map,
or
null
if this map is empty
pollLastEntry
public java.util.Map.Entry pollLastEntry()
Removes and returns a key-value mapping associated with
the greatest key in this map, or null
if the map is empty.
- the removed last entry of this map,
or
null
if this map is empty
subMap
public SortedMap subMap(K fromKey,
K toKey)
Equivalent to subMap(fromKey, true, toKey, false)
.
subMap
public NavigableMap subMap(K fromKey,
boolean fromInclusive,
K toKey,
boolean toInclusive)
Returns a view of the portion of this map whose keys range from
fromKey
to
toKey
. If
fromKey
and
toKey
are equal, the returned map is empty unless
fromExclusive
and
toExclusive
are both true. The
returned map is backed by this map, so changes in the returned map are
reflected in this map, and vice-versa. The returned map supports all
optional map operations that this map supports.
The returned map will throw an
IllegalArgumentException
on an attempt to insert a key outside of its range, or to construct a
submap either of whose endpoints lie outside its range.
fromKey
- low endpoint of the keys in the returned mapfromInclusive
- true
if the low endpoint
is to be included in the returned viewtoKey
- high endpoint of the keys in the returned maptoInclusive
- true
if the high endpoint
is to be included in the returned view
- a view of the portion of this map whose keys range from
fromKey
to toKey
ClassCastException
- if fromKey
and toKey
cannot be compared to one another using this map's comparator
(or, if the map has no comparator, using natural ordering).
Implementations may, but are not required to, throw this
exception if fromKey
or toKey
cannot be compared to keys currently in the map.NullPointerException
- if fromKey
or toKey
is null and this map does not permit null keysIllegalArgumentException
- if fromKey
is greater than
toKey
; or if this map itself has a restricted
range, and fromKey
or toKey
lies
outside the bounds of the range
tailMap
public SortedMap tailMap(K fromKey)
Equivalent to tailMap(fromKey, true)
.
tailMap
public NavigableMap tailMap(K fromKey,
boolean inclusive)
Returns a view of the portion of this map whose keys are greater than (or
equal to, if
inclusive
is true)
fromKey
. The returned
map is backed by this map, so changes in the returned map are reflected
in this map, and vice-versa. The returned map supports all optional
map operations that this map supports.
The returned map will throw an
IllegalArgumentException
on an attempt to insert a key outside its range.
fromKey
- low endpoint of the keys in the returned mapinclusive
- true
if the low endpoint
is to be included in the returned view
- a view of the portion of this map whose keys are greater than
(or equal to, if
inclusive
is true) fromKey
ClassCastException
- if fromKey
is not compatible
with this map's comparator (or, if the map has no comparator,
if fromKey
does not implement Comparable
).
Implementations may, but are not required to, throw this
exception if fromKey
cannot be compared to keys
currently in the map.NullPointerException
- if fromKey
is null
and this map does not permit null keysIllegalArgumentException
- if this map itself has a
restricted range, and fromKey
lies outside the
bounds of the range