- Type Parameters:
K
- the type of keys maintained by this mapV
- the type of mapped values
- All Implemented Interfaces:
Serializable
,Cloneable
,Map<K,
,V> NavigableMap<K,
,V> SequencedMap<K,
,V> SortedMap<K,
V>
NavigableMap
implementation.
The map is sorted according to the natural
ordering of its keys, or by a Comparator
provided at map
creation time, depending on which constructor is used.
This implementation provides guaranteed log(n) time cost for the
containsKey
, get
, put
and remove
operations. Algorithms are adaptations of those in Cormen, Leiserson, and
Rivest's Introduction to Algorithms.
Note that the ordering maintained by a tree map, like any sorted map, and
whether or not an explicit comparator is provided, must be consistent
with equals
if this sorted map is to correctly implement the
Map
interface. (See Comparable
or Comparator
for a
precise definition of consistent with equals.) This is so because
the Map
interface is defined in terms of the equals
operation, but a sorted map 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 sorted map, equal. The behavior
of a sorted map is well-defined even if its ordering is
inconsistent with equals
; it just fails to obey the general contract
of the Map
interface.
Note that this implementation is not synchronized.
If multiple threads access a map concurrently, and at least one of the
threads modifies the map structurally, it must be synchronized
externally. (A structural modification is any operation that adds or
deletes one or more mappings; merely changing the value associated
with an existing key is not a structural modification.) This is
typically accomplished by synchronizing on some object that naturally
encapsulates the map.
If no such object exists, the map should be "wrapped" using the
Collections.synchronizedSortedMap
method. This is best done at creation time, to prevent accidental
unsynchronized access to the map:
SortedMap m = Collections.synchronizedSortedMap(new TreeMap(...));
The iterators returned by the iterator
method of the collections
returned by all of this class's "collection view methods" are
fail-fast: if the map is structurally modified at any time after
the iterator is created, in any way except through the iterator's own
remove
method, the iterator will throw a ConcurrentModificationException
. Thus, in the face of concurrent
modification, the iterator fails quickly and cleanly, rather than risking
arbitrary, non-deterministic behavior at an undetermined time in the future.
Note that the fail-fast behavior of an iterator cannot be guaranteed
as it is, generally speaking, impossible to make any hard guarantees in the
presence of unsynchronized concurrent modification. Fail-fast iterators
throw ConcurrentModificationException
on a best-effort basis.
Therefore, it would be wrong to write a program that depended on this
exception for its correctness: the fail-fast behavior of iterators
should be used only to detect bugs.
The methods
ceilingEntry(K)
,
firstEntry()
,
floorEntry(K)
,
higherEntry(K)
,
lastEntry()
,
lowerEntry(K)
,
pollFirstEntry()
, and
pollLastEntry()
return Map.Entry
instances that represent snapshots of mappings as
of the time of the call. They do not support mutation of the
underlying map via the optional setValue
method.
The putFirst
and putLast
methods of this class
throw UnsupportedOperationException
. The encounter order of mappings is determined
by the comparison method; therefore, explicit positioning is not supported.
This class is a member of the Java Collections Framework.
- Since:
- 1.2
- See Also:
-
Nested Class Summary
Nested classes/interfaces declared in class java.util.AbstractMap
AbstractMap.SimpleEntry<K,
V>, AbstractMap.SimpleImmutableEntry<K, V> -
Constructor Summary
ConstructorDescriptionTreeMap()
Constructs a new, empty tree map, using the natural ordering of its keys.TreeMap
(Comparator<? super K> comparator) Constructs a new, empty tree map, ordered according to the given comparator.Constructs a new tree map containing the same mappings as the given map, ordered according to the natural ordering of its keys.Constructs a new tree map containing the same mappings and using the same ordering as the specified sorted map. -
Method Summary
Modifier and TypeMethodDescriptionceilingEntry
(K key) Returns a key-value mapping associated with the least key greater than or equal to the given key, ornull
if there is no such key.ceilingKey
(K key) Returns the least key greater than or equal to the given key, ornull
if there is no such key.void
clear()
Removes all of the mappings from this map.clone()
Returns a shallow copy of thisTreeMap
instance.Comparator
<? super K> Returns the comparator used to order the keys in this map, ornull
if this map uses the natural ordering of its keys.Attempts to compute a mapping for the specified key and its current mapped value, ornull
if there is no current mapping (optional operation).computeIfAbsent
(K key, Function<? super K, ? extends V> mappingFunction) If the specified key is not already associated with a value (or is mapped tonull
), attempts to compute its value using the given mapping function and enters it into this map unlessnull
(optional operation).computeIfPresent
(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value (optional operation).boolean
containsKey
(Object key) Returnstrue
if this map contains a mapping for the specified key.boolean
containsValue
(Object value) Returnstrue
if this map maps one or more keys to the specified value.Returns a reverse orderNavigableSet
view of the keys contained in this map.Returns a reverse order view of the mappings contained in this map.entrySet()
Returns aSet
view of the mappings contained in this map.Returns a key-value mapping associated with the least key in this map, ornull
if the map is empty.firstKey()
Returns the first (lowest) key currently in this map.floorEntry
(K key) Returns a key-value mapping associated with the greatest key less than or equal to the given key, ornull
if there is no such key.Returns the greatest key less than or equal to the given key, ornull
if there is no such key.Returns the value to which the specified key is mapped, ornull
if this map contains no mapping for the key.Returns a view of the portion of this map whose keys are strictly less thantoKey
.Returns a view of the portion of this map whose keys are less than (or equal to, ifinclusive
is true)toKey
.higherEntry
(K key) Returns a key-value mapping associated with the least key strictly greater than the given key, ornull
if there is no such key.Returns the least key strictly greater than the given key, ornull
if there is no such key.keySet()
Returns aSet
view of the keys contained in this map.Returns a key-value mapping associated with the greatest key in this map, ornull
if the map is empty.lastKey()
Returns the last (highest) key currently in this map.lowerEntry
(K key) Returns a key-value mapping associated with the greatest key strictly less than the given key, ornull
if there is no such key.Returns the greatest key strictly less than the given key, ornull
if there is no such key.If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value (optional operation).Returns aNavigableSet
view of the keys contained in this map.Removes and returns a key-value mapping associated with the least key in this map, ornull
if the map is empty (optional operation).Removes and returns a key-value mapping associated with the greatest key in this map, ornull
if the map is empty (optional operation).Associates the specified value with the specified key in this map.void
Copies all of the mappings from the specified map to this map.ThrowsUnsupportedOperationException
.ThrowsUnsupportedOperationException
.Removes the mapping for this key from this TreeMap if present.int
size()
Returns the number of key-value mappings in this map.Returns a view of the portion of this map whose keys range fromfromKey
totoKey
.Returns a view of the portion of this map whose keys range fromfromKey
, inclusive, totoKey
, exclusive.Returns a view of the portion of this map whose keys are greater than or equal tofromKey
.Returns a view of the portion of this map whose keys are greater than (or equal to, ifinclusive
is true)fromKey
.values()
Returns aCollection
view of the values contained in this map.Methods declared in class java.util.AbstractMap
equals, hashCode, isEmpty, toString
Methods declared in interface java.util.Map
equals, forEach, getOrDefault, hashCode, isEmpty, putIfAbsent, remove, replace, replace, replaceAll
Methods declared in interface java.util.NavigableMap
reversed
Methods declared in interface java.util.SequencedMap
sequencedEntrySet, sequencedKeySet, sequencedValues
-
Constructor Details
-
TreeMap
public TreeMap()Constructs a new, empty tree map, using the natural ordering of its keys. All keys inserted into the map must implement theComparable
interface. Furthermore, all such keys must be mutually comparable:k1.compareTo(k2)
must not throw aClassCastException
for any keysk1
andk2
in the map. If the user attempts to put a key into the map that violates this constraint (for example, the user attempts to put a string key into a map whose keys are integers), theput(Object key, Object value)
call will throw aClassCastException
. -
TreeMap
Constructs a new, empty tree map, ordered according to the given comparator. All keys inserted into the map must be mutually comparable by the given comparator:comparator.compare(k1, k2)
must not throw aClassCastException
for any keysk1
andk2
in the map. If the user attempts to put a key into the map that violates this constraint, theput(Object key, Object value)
call will throw aClassCastException
.- Parameters:
comparator
- the comparator that will be used to order this map. Ifnull
, the natural ordering of the keys will be used.
-
TreeMap
Constructs a new tree map containing the same mappings as the given map, ordered according to the natural ordering of its keys. All keys inserted into the new map must implement theComparable
interface. Furthermore, all such keys must be mutually comparable:k1.compareTo(k2)
must not throw aClassCastException
for any keysk1
andk2
in the map. This method runs in n*log(n) time.- Parameters:
m
- the map whose mappings are to be placed in this map- Throws:
ClassCastException
- if the keys in m are notComparable
, or are not mutually comparableNullPointerException
- if the specified map is null
-
TreeMap
Constructs a new tree map containing the same mappings and using the same ordering as the specified sorted map. This method runs in linear time.- Parameters:
m
- the sorted map whose mappings are to be placed in this map, and whose comparator is to be used to sort this map- Throws:
NullPointerException
- if the specified map is null
-
-
Method Details
-
size
-
containsKey
Returnstrue
if this map contains a mapping for the specified key.- Specified by:
containsKey
in interfaceMap<K,
V> - Overrides:
containsKey
in classAbstractMap<K,
V> - Parameters:
key
- key whose presence in this map is to be tested- Returns:
true
if this map contains a mapping for the specified key- Throws:
ClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys
-
containsValue
Returnstrue
if this map maps one or more keys to the specified value. More formally, returnstrue
if and only if this map contains at least one mapping to a valuev
such that(value==null ? v==null : value.equals(v))
. This operation will probably require time linear in the map size for most implementations.- Specified by:
containsValue
in interfaceMap<K,
V> - Overrides:
containsValue
in classAbstractMap<K,
V> - Parameters:
value
- value whose presence in this map is to be tested- Returns:
true
if a mapping tovalue
exists;false
otherwise- Since:
- 1.2
-
get
Returns the value to which the specified key is mapped, ornull
if this map contains no mapping for the key.More formally, if this map contains a mapping from a key
k
to a valuev
such thatkey
compares equal tok
according to the map's ordering, then this method returnsv
; otherwise it returnsnull
. (There can be at most one such mapping.)A return value of
null
does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key tonull
. ThecontainsKey
operation may be used to distinguish these two cases.- Specified by:
get
in interfaceMap<K,
V> - Overrides:
get
in classAbstractMap<K,
V> - Parameters:
key
- the key whose associated value is to be returned- Returns:
- the value to which the specified key is mapped, or
null
if this map contains no mapping for the key - Throws:
ClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys
-
comparator
Description copied from interface:SortedMap
Returns the comparator used to order the keys in this map, ornull
if this map uses the natural ordering of its keys.- Specified by:
comparator
in interfaceSortedMap<K,
V> - Returns:
- the comparator used to order the keys in this map,
or
null
if this map uses the natural ordering of its keys
-
firstKey
-
lastKey
-
putFirst
ThrowsUnsupportedOperationException
. The encounter order induced by this map's comparison method determines the position of mappings, so explicit positioning is not supported.- Specified by:
putFirst
in interfaceSequencedMap<K,
V> - Specified by:
putFirst
in interfaceSortedMap<K,
V> - Parameters:
k
- the keyv
- the value- Returns:
- the value previously associated with k, or null if none
- Throws:
UnsupportedOperationException
- always- Since:
- 21
-
putLast
ThrowsUnsupportedOperationException
. The encounter order induced by this map's comparison method determines the position of mappings, so explicit positioning is not supported.- Specified by:
putLast
in interfaceSequencedMap<K,
V> - Specified by:
putLast
in interfaceSortedMap<K,
V> - Parameters:
k
- the keyv
- the value- Returns:
- the value previously associated with k, or null if none
- Throws:
UnsupportedOperationException
- always- Since:
- 21
-
putAll
Copies all of the mappings from the specified map to this map. These mappings replace any mappings that this map had for any of the keys currently in the specified map.- Specified by:
putAll
in interfaceMap<K,
V> - Overrides:
putAll
in classAbstractMap<K,
V> - Parameters:
map
- mappings to be stored in this map- Throws:
ClassCastException
- if the class of a key or value in the specified map prevents it from being stored in this mapNullPointerException
- if the specified map is null or the specified map contains a null key and this map does not permit null keys
-
put
Associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced.- Specified by:
put
in interfaceMap<K,
V> - Overrides:
put
in classAbstractMap<K,
V> - Parameters:
key
- key with which the specified value is to be associatedvalue
- value to be associated with the specified key- Returns:
- the previous value associated with
key
, ornull
if there was no mapping forkey
. (Anull
return can also indicate that the map previously associatednull
withkey
.) - Throws:
ClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys
-
computeIfAbsent
If the specified key is not already associated with a value (or is mapped tonull
), attempts to compute its value using the given mapping function and enters it into this map unlessnull
(optional operation).If the mapping function returns
null
, no mapping is recorded. If the mapping function itself throws an (unchecked) exception, the exception is rethrown, and no mapping is recorded. The most common usage is to construct a new object serving as an initial mapped value or memoized result, as in:map.computeIfAbsent(key, k -> new Value(f(k)));
Or to implement a multi-value map,
Map<K,Collection<V>>
, supporting multiple values per key:map.computeIfAbsent(key, k -> new HashSet<V>()).add(v);
The mapping function should not modify this map during computation.
This method will, on a best-effort basis, throw a
ConcurrentModificationException
if it is detected that the mapping function modifies this map during computation.- Specified by:
computeIfAbsent
in interfaceMap<K,
V> - Parameters:
key
- key with which the specified value is to be associatedmappingFunction
- the mapping function to compute a value- Returns:
- the current (existing or computed) value associated with the specified key, or null if the computed value is null
- Throws:
ConcurrentModificationException
- if it is detected that the mapping function modified this map
-
computeIfPresent
If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value (optional operation).If the remapping function returns
null
, the mapping is removed. If the remapping function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.The remapping function should not modify this map during computation.
This method will, on a best-effort basis, throw a
ConcurrentModificationException
if it is detected that the remapping function modifies this map during computation.- Specified by:
computeIfPresent
in interfaceMap<K,
V> - Parameters:
key
- key with which the specified value is to be associatedremappingFunction
- the remapping function to compute a value- Returns:
- the new value associated with the specified key, or null if none
- Throws:
ConcurrentModificationException
- if it is detected that the remapping function modified this map
-
compute
Attempts to compute a mapping for the specified key and its current mapped value, ornull
if there is no current mapping (optional operation). For example, to either create or append aString
msg to a value mapping:map.compute(key, (k, v) -> (v == null) ? msg : v.concat(msg))
merge()
is often simpler to use for such purposes.)If the remapping function returns
null
, the mapping is removed (or remains absent if initially absent). If the remapping function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.The remapping function should not modify this map during computation.
This method will, on a best-effort basis, throw a
ConcurrentModificationException
if it is detected that the remapping function modifies this map during computation.- Specified by:
compute
in interfaceMap<K,
V> - Parameters:
key
- key with which the specified value is to be associatedremappingFunction
- the remapping function to compute a value- Returns:
- the new value associated with the specified key, or null if none
- Throws:
ConcurrentModificationException
- if it is detected that the remapping function modified this map
-
merge
If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value (optional operation). Otherwise, replaces the associated value with the results of the given remapping function, or removes if the result isnull
. This method may be of use when combining multiple mapped values for a key. For example, to either create or append aString msg
to a value mapping:map.merge(key, msg, String::concat)
If the remapping function returns
null
, the mapping is removed. If the remapping function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.The remapping function should not modify this map during computation.
This method will, on a best-effort basis, throw a
ConcurrentModificationException
if it is detected that the remapping function modifies this map during computation.- Specified by:
merge
in interfaceMap<K,
V> - Parameters:
key
- key with which the resulting value is to be associatedvalue
- the non-null value to be merged with the existing value associated with the key or, if no existing value or a null value is associated with the key, to be associated with the keyremappingFunction
- the remapping function to recompute a value if present- Returns:
- the new value associated with the specified key, or null if no value is associated with the key
- Throws:
ConcurrentModificationException
- if it is detected that the remapping function modified this map
-
remove
Removes the mapping for this key from this TreeMap if present.- Specified by:
remove
in interfaceMap<K,
V> - Overrides:
remove
in classAbstractMap<K,
V> - Parameters:
key
- key for which mapping should be removed- Returns:
- the previous value associated with
key
, ornull
if there was no mapping forkey
. (Anull
return can also indicate that the map previously associatednull
withkey
.) - Throws:
ClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys
-
clear
-
clone
Returns a shallow copy of thisTreeMap
instance. (The keys and values themselves are not cloned.)- Overrides:
clone
in classAbstractMap<K,
V> - Returns:
- a shallow copy of this map
- See Also:
-
firstEntry
Description copied from interface:NavigableMap
Returns a key-value mapping associated with the least key in this map, ornull
if the map is empty.- Specified by:
firstEntry
in interfaceNavigableMap<K,
V> - Specified by:
firstEntry
in interfaceSequencedMap<K,
V> - Returns:
- an entry with the least key,
or
null
if this map is empty - Since:
- 1.6
-
lastEntry
Description copied from interface:NavigableMap
Returns a key-value mapping associated with the greatest key in this map, ornull
if the map is empty.- Specified by:
lastEntry
in interfaceNavigableMap<K,
V> - Specified by:
lastEntry
in interfaceSequencedMap<K,
V> - Returns:
- an entry with the greatest key,
or
null
if this map is empty - Since:
- 1.6
-
pollFirstEntry
Description copied from interface:NavigableMap
Removes and returns a key-value mapping associated with the least key in this map, ornull
if the map is empty (optional operation).- Specified by:
pollFirstEntry
in interfaceNavigableMap<K,
V> - Specified by:
pollFirstEntry
in interfaceSequencedMap<K,
V> - Returns:
- the removed first entry of this map,
or
null
if this map is empty - Since:
- 1.6
-
pollLastEntry
Description copied from interface:NavigableMap
Removes and returns a key-value mapping associated with the greatest key in this map, ornull
if the map is empty (optional operation).- Specified by:
pollLastEntry
in interfaceNavigableMap<K,
V> - Specified by:
pollLastEntry
in interfaceSequencedMap<K,
V> - Returns:
- the removed last entry of this map,
or
null
if this map is empty - Since:
- 1.6
-
lowerEntry
Description copied from interface:NavigableMap
Returns a key-value mapping associated with the greatest key strictly less than the given key, ornull
if there is no such key.- Specified by:
lowerEntry
in interfaceNavigableMap<K,
V> - Parameters:
key
- the key- Returns:
- an entry with the greatest key less than
key
, ornull
if there is no such key - Throws:
ClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys- Since:
- 1.6
-
lowerKey
Description copied from interface:NavigableMap
Returns the greatest key strictly less than the given key, ornull
if there is no such key.- Specified by:
lowerKey
in interfaceNavigableMap<K,
V> - Parameters:
key
- the key- Returns:
- the greatest key less than
key
, ornull
if there is no such key - Throws:
ClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys- Since:
- 1.6
-
floorEntry
Description copied from interface:NavigableMap
Returns a key-value mapping associated with the greatest key less than or equal to the given key, ornull
if there is no such key.- Specified by:
floorEntry
in interfaceNavigableMap<K,
V> - Parameters:
key
- the key- Returns:
- an entry with the greatest key less than or equal to
key
, ornull
if there is no such key - Throws:
ClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys- Since:
- 1.6
-
floorKey
Description copied from interface:NavigableMap
Returns the greatest key less than or equal to the given key, ornull
if there is no such key.- Specified by:
floorKey
in interfaceNavigableMap<K,
V> - Parameters:
key
- the key- Returns:
- the greatest key less than or equal to
key
, ornull
if there is no such key - Throws:
ClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys- Since:
- 1.6
-
ceilingEntry
Description copied from interface:NavigableMap
Returns a key-value mapping associated with the least key greater than or equal to the given key, ornull
if there is no such key.- Specified by:
ceilingEntry
in interfaceNavigableMap<K,
V> - Parameters:
key
- the key- Returns:
- an entry with the least key greater than or equal to
key
, ornull
if there is no such key - Throws:
ClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys- Since:
- 1.6
-
ceilingKey
Description copied from interface:NavigableMap
Returns the least key greater than or equal to the given key, ornull
if there is no such key.- Specified by:
ceilingKey
in interfaceNavigableMap<K,
V> - Parameters:
key
- the key- Returns:
- the least key greater than or equal to
key
, ornull
if there is no such key - Throws:
ClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys- Since:
- 1.6
-
higherEntry
Description copied from interface:NavigableMap
Returns a key-value mapping associated with the least key strictly greater than the given key, ornull
if there is no such key.- Specified by:
higherEntry
in interfaceNavigableMap<K,
V> - Parameters:
key
- the key- Returns:
- an entry with the least key greater than
key
, ornull
if there is no such key - Throws:
ClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys- Since:
- 1.6
-
higherKey
Description copied from interface:NavigableMap
Returns the least key strictly greater than the given key, ornull
if there is no such key.- Specified by:
higherKey
in interfaceNavigableMap<K,
V> - Parameters:
key
- the key- Returns:
- the least key greater than
key
, ornull
if there is no such key - Throws:
ClassCastException
- if the specified key cannot be compared with the keys currently in the mapNullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys- Since:
- 1.6
-
keySet
Returns aSet
view of the keys contained in this map.The set's iterator returns the keys in ascending order. The set's spliterator is late-binding, fail-fast, and additionally reports
Spliterator.SORTED
andSpliterator.ORDERED
with an encounter order that is ascending key order. The spliterator's comparator (seeSpliterator.getComparator()
) isnull
if the tree map's comparator (seecomparator()
) isnull
. Otherwise, the spliterator's comparator is the same as or imposes the same total ordering as the tree map's comparator.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 theIterator.remove
,Set.remove
,removeAll
,retainAll
, andclear
operations. It does not support theadd
oraddAll
operations. -
descendingKeySet
Description copied from interface:NavigableMap
Returns a reverse orderNavigableSet
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 ownremove
operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via theIterator.remove
,Set.remove
,removeAll
,retainAll
, andclear
operations. It does not support theadd
oraddAll
operations.- Specified by:
descendingKeySet
in interfaceNavigableMap<K,
V> - Returns:
- a reverse order navigable set view of the keys in this map
- Since:
- 1.6
-
values
Returns aCollection
view of the values contained in this map.The collection's iterator returns the values in ascending order of the corresponding keys. The collection's spliterator is late-binding, fail-fast, and additionally reports
Spliterator.ORDERED
with an encounter order that is ascending order of the corresponding keys.The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. If the map is modified while an iteration over the collection is in progress (except through the iterator's own
remove
operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via theIterator.remove
,Collection.remove
,removeAll
,retainAll
andclear
operations. It does not support theadd
oraddAll
operations. -
entrySet
Returns aSet
view of the mappings contained in this map.The set's iterator returns the entries in ascending key order. The set's spliterator is late-binding, fail-fast, and additionally reports
Spliterator.SORTED
andSpliterator.ORDERED
with an encounter order that is ascending key 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, or through thesetValue
operation on a map entry returned by the iterator) the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via theIterator.remove
,Set.remove
,removeAll
,retainAll
andclear
operations. It does not support theadd
oraddAll
operations. -
descendingMap
Description copied from interface:NavigableMap
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 ownremove
operation), the results of the iteration are undefined.The returned map has an ordering equivalent to
Collections.reverseOrder
(comparator())
. The expressionm.descendingMap().descendingMap()
returns a view ofm
essentially equivalent tom
.- Specified by:
descendingMap
in interfaceNavigableMap<K,
V> - Returns:
- a reverse order view of this map
- Since:
- 1.6
-
subMap
Description copied from interface:NavigableMap
Returns a view of the portion of this map whose keys range fromfromKey
totoKey
. IffromKey
andtoKey
are equal, the returned map is empty unlessfromInclusive
andtoInclusive
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.- Specified by:
subMap
in interfaceNavigableMap<K,
V> - Parameters:
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- Returns:
- a view of the portion of this map whose keys range from
fromKey
totoKey
- Throws:
ClassCastException
- iffromKey
andtoKey
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 iffromKey
ortoKey
cannot be compared to keys currently in the map.NullPointerException
- iffromKey
ortoKey
is null and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException
- iffromKey
is greater thantoKey
; or if this map itself has a restricted range, andfromKey
ortoKey
lies outside the bounds of the range- Since:
- 1.6
-
headMap
Description copied from interface:NavigableMap
Returns a view of the portion of this map whose keys are less than (or equal to, ifinclusive
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.- Specified by:
headMap
in interfaceNavigableMap<K,
V> - Parameters:
toKey
- high endpoint of the keys in the returned mapinclusive
-true
if the high endpoint is to be included in the returned view- Returns:
- a view of the portion of this map whose keys are less than
(or equal to, if
inclusive
is true)toKey
- Throws:
ClassCastException
- iftoKey
is not compatible with this map's comparator (or, if the map has no comparator, iftoKey
does not implementComparable
). Implementations may, but are not required to, throw this exception iftoKey
cannot be compared to keys currently in the map.NullPointerException
- iftoKey
is null and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException
- if this map itself has a restricted range, andtoKey
lies outside the bounds of the range- Since:
- 1.6
-
tailMap
Description copied from interface:NavigableMap
Returns a view of the portion of this map whose keys are greater than (or equal to, ifinclusive
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.- Specified by:
tailMap
in interfaceNavigableMap<K,
V> - Parameters:
fromKey
- low endpoint of the keys in the returned mapinclusive
-true
if the low endpoint is to be included in the returned view- Returns:
- a view of the portion of this map whose keys are greater than
(or equal to, if
inclusive
is true)fromKey
- Throws:
ClassCastException
- iffromKey
is not compatible with this map's comparator (or, if the map has no comparator, iffromKey
does not implementComparable
). Implementations may, but are not required to, throw this exception iffromKey
cannot be compared to keys currently in the map.NullPointerException
- iffromKey
is null and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException
- if this map itself has a restricted range, andfromKey
lies outside the bounds of the range- Since:
- 1.6
-
subMap
Description copied from interface:NavigableMap
Returns a view of the portion of this map whose keys range fromfromKey
, inclusive, totoKey
, exclusive. (IffromKey
andtoKey
are equal, the returned map is empty.) 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.Equivalent to
subMap(fromKey, true, toKey, false)
.- Specified by:
subMap
in interfaceNavigableMap<K,
V> - Specified by:
subMap
in interfaceSortedMap<K,
V> - Parameters:
fromKey
- low endpoint (inclusive) of the keys in the returned maptoKey
- high endpoint (exclusive) of the keys in the returned map- Returns:
- a view of the portion of this map whose keys range from
fromKey
, inclusive, totoKey
, exclusive - Throws:
ClassCastException
- iffromKey
andtoKey
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 iffromKey
ortoKey
cannot be compared to keys currently in the map.NullPointerException
- iffromKey
ortoKey
is null and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException
- iffromKey
is greater thantoKey
; or if this map itself has a restricted range, andfromKey
ortoKey
lies outside the bounds of the range
-
headMap
Description copied from interface:NavigableMap
Returns a view of the portion of this map whose keys are strictly less thantoKey
. 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.Equivalent to
headMap(toKey, false)
.- Specified by:
headMap
in interfaceNavigableMap<K,
V> - Specified by:
headMap
in interfaceSortedMap<K,
V> - Parameters:
toKey
- high endpoint (exclusive) of the keys in the returned map- Returns:
- a view of the portion of this map whose keys are strictly
less than
toKey
- Throws:
ClassCastException
- iftoKey
is not compatible with this map's comparator (or, if the map has no comparator, iftoKey
does not implementComparable
). Implementations may, but are not required to, throw this exception iftoKey
cannot be compared to keys currently in the map.NullPointerException
- iftoKey
is null and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException
- if this map itself has a restricted range, andtoKey
lies outside the bounds of the range
-
tailMap
Description copied from interface:NavigableMap
Returns a view of the portion of this map whose keys are greater than or equal tofromKey
. 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.Equivalent to
tailMap(fromKey, true)
.- Specified by:
tailMap
in interfaceNavigableMap<K,
V> - Specified by:
tailMap
in interfaceSortedMap<K,
V> - Parameters:
fromKey
- low endpoint (inclusive) of the keys in the returned map- Returns:
- a view of the portion of this map whose keys are greater
than or equal to
fromKey
- Throws:
ClassCastException
- iffromKey
is not compatible with this map's comparator (or, if the map has no comparator, iffromKey
does not implementComparable
). Implementations may, but are not required to, throw this exception iffromKey
cannot be compared to keys currently in the map.NullPointerException
- iffromKey
is null and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException
- if this map itself has a restricted range, andfromKey
lies outside the bounds of the range
-