A
java.util.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 Map.Entry ceilingEntry(Object 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 Object ceilingKey(Object 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 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 Map.Entry floorEntry(Object 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 Object floorKey(Object 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(Object toKey)
Equivalent to headMap(toKey, false).
headMap
public NavigableMap headMap(Object 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
higherEntry
public Map.Entry higherEntry(Object 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 Object higherKey(Object 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 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 Map.Entry lowerEntry(Object 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 Object lowerKey(Object 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 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 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(Object fromKey,
Object toKey)
Equivalent to subMap(fromKey, true, toKey, false).
subMap
public NavigableMap subMap(Object fromKey,
boolean fromInclusive,
Object 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
tailMap
public SortedMap tailMap(Object fromKey)
Equivalent to tailMap(fromKey, true).
tailMap
public NavigableMap tailMap(Object 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