TreeMap
public
class
TreeMap
extends AbstractMap<K, V>
implements
NavigableMap<K, V>,
Cloneable,
Serializable
java.lang.Object | ||
↳ | java.util.AbstractMap<K, V> | |
↳ | java.util.TreeMap<K, V> |
A Red-Black tree based NavigableMap
implementation.
The map is sorted according to the 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.
Summary
Public constructors | |
---|---|
TreeMap()
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. |
|
TreeMap(Map<? extends K, ? extends V> m)
Constructs a new tree map containing the same mappings as the given map, ordered according to the natural ordering of its keys. |
|
TreeMap(SortedMap<K, ? extends V> m)
Constructs a new tree map containing the same mappings and using the same ordering as the specified sorted map. |
Public methods | |
---|---|
Entry<K, V>
|
ceilingEntry(K key)
Returns a key-value mapping associated with the least key
greater than or equal to the given key, or |
K
|
ceilingKey(K key)
Returns the least key greater than or equal to the given key,
or |
void
|
clear()
Removes all of the mappings from this map. |
Object
|
clone()
Returns a shallow copy of this |
Comparator<? super K>
|
comparator()
Returns the comparator used to order the keys in this map, or
|
V
|
compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction)
Attempts to compute a mapping for the specified key and its current
mapped value (or This method will, on a best-effort basis, throw a
|
V
|
computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction)
If the specified key is not already associated with a value (or is mapped
to This method will, on a best-effort basis, throw a
|
V
|
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. This method will, on a best-effort basis, throw a
|
boolean
|
containsKey(Object key)
Returns |
boolean
|
containsValue(Object value)
Returns |
NavigableSet<K>
|
descendingKeySet()
Returns a reverse order |
NavigableMap<K, V>
|
descendingMap()
Returns a reverse order view of the mappings contained in this map. |
Set<Entry<K, V>>
|
entrySet()
Returns a |
Entry<K, V>
|
firstEntry()
Returns a key-value mapping associated with the least
key in this map, or |
K
|
firstKey()
Returns the first (lowest) key currently in this map. |
Entry<K, V>
|
floorEntry(K key)
Returns a key-value mapping associated with the greatest key
less than or equal to the given key, or |
K
|
floorKey(K key)
Returns the greatest key less than or equal to the given key,
or |
void
|
forEach(BiConsumer<? super K, ? super V> action)
Performs the given action for each entry in this map until all entries have been processed or the action throws an exception. |
V
|
get(Object key)
Returns the value to which the specified key is mapped,
or |
SortedMap<K, V>
|
headMap(K toKey)
Returns a view of the portion of this map whose keys are
strictly less than Equivalent to |
NavigableMap<K, V>
|
headMap(K toKey, boolean inclusive)
Returns a view of the portion of this map whose keys are less than (or
equal to, if |
Entry<K, V>
|
higherEntry(K key)
Returns a key-value mapping associated with the least key
strictly greater than the given key, or |
K
|
higherKey(K key)
Returns the least key strictly greater than the given key, or
|
Set<K>
|
keySet()
Returns a |
Entry<K, V>
|
lastEntry()
Returns a key-value mapping associated with the greatest
key in this map, or |
K
|
lastKey()
Returns the last (highest) key currently in this map. |
Entry<K, V>
|
lowerEntry(K key)
Returns a key-value mapping associated with the greatest key
strictly less than the given key, or |
K
|
lowerKey(K key)
Returns the greatest key strictly less than the given key, or
|
V
|
merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction)
If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value. This method will, on a best-effort basis, throw a
|
NavigableSet<K>
|
navigableKeySet()
Returns a |
Entry<K, V>
|
pollFirstEntry()
Removes and returns a key-value mapping associated with
the least key in this map, or |
Entry<K, V>
|
pollLastEntry()
Removes and returns a key-value mapping associated with
the greatest key in this map, or |
V
|
put(K key, V value)
Associates the specified value with the specified key in this map. |
void
|
putAll(Map<? extends K, ? extends V> map)
Copies all of the mappings from the specified map to this map. |
V
|
putFirst(K k, V v)
Throws |
V
|
putIfAbsent(K key, V value)
If the specified key is not already associated with a value (or is mapped
to |
V
|
putLast(K k, V v)
Throws |
V
|
remove(Object key)
Removes the mapping for this key from this TreeMap if present. |
boolean
|
replace(K key, V oldValue, V newValue)
Replaces the entry for the specified key only if currently mapped to the specified value. |
V
|
replace(K key, V value)
Replaces the entry for the specified key only if it is currently mapped to some value. |
void
|
replaceAll(BiFunction<? super K, ? super V, ? extends V> function)
Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception. |
int
|
size()
Returns the number of key-value mappings in this map. |
SortedMap<K, V>
|
subMap(K fromKey, K toKey)
Returns a view of the portion of this map whose keys range from
Equivalent to |
NavigableMap<K, V>
|
subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive)
Returns a view of the portion of this map whose keys range from
|
NavigableMap<K, V>
|
tailMap(K fromKey, boolean inclusive)
Returns a view of the portion of this map whose keys are greater than (or
equal to, if |
SortedMap<K, V>
|
tailMap(K fromKey)
Returns a view of the portion of this map whose keys are
greater than or equal to Equivalent to |
Collection<V>
|
values()
Returns a |
Inherited methods | |
---|---|
Public constructors
TreeMap
public TreeMap ()
Constructs a new, empty tree map, using the natural ordering of its
keys. All keys inserted into the map must implement the Comparable
interface. Furthermore, all such keys must be
mutually comparable: k1.compareTo(k2)
must not throw
a ClassCastException
for any keys k1
and
k2
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), the
put(Object key, Object value)
call will throw a
ClassCastException
.
TreeMap
public TreeMap (Comparator<? super K> comparator)
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 a ClassCastException
for any keys
k1
and k2
in the map. If the user attempts to put
a key into the map that violates this constraint, the put(Object
key, Object value)
call will throw a
ClassCastException
.
Parameters | |
---|---|
comparator |
Comparator : the comparator that will be used to order this map.
If null , the ordering of the keys will be used. |
TreeMap
public TreeMap (Map<? extends K, ? extends V> m)
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 the Comparable
interface. Furthermore, all such keys must be
mutually comparable: k1.compareTo(k2)
must not throw
a ClassCastException
for any keys k1
and
k2
in the map. This method runs in n*log(n) time.
Parameters | |
---|---|
m |
Map : the map whose mappings are to be placed in this map |
Throws | |
---|---|
ClassCastException |
if the keys in m are not Comparable ,
or are not mutually comparable |
NullPointerException |
if the specified map is null |
TreeMap
public TreeMap (SortedMap<K, ? extends V> m)
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 |
SortedMap : 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 |
Public methods
ceilingEntry
public Entry<K, V> 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.
Parameters | |
---|---|
key |
K : the key |
Returns | |
---|---|
Entry<K, V> |
an entry with the least key greater than or equal to
key , or null if there is no such key |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys |
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.
Parameters | |
---|---|
key |
K : the key |
Returns | |
---|---|
K |
the least key greater than or equal to key ,
or null if there is no such key |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys |
clear
public void clear ()
Removes all of the mappings from this map. The map will be empty after this call returns.
clone
public Object clone ()
Returns a shallow copy of this TreeMap
instance. (The keys and
values themselves are not cloned.)
Returns | |
---|---|
Object |
a shallow copy of this map |
comparator
public Comparator<? super K> comparator ()
Returns the comparator used to order the keys in this map, or
null
if this map uses the natural ordering of its keys.
Returns | |
---|---|
Comparator<? super K> |
the comparator used to order the keys in this map,
or null if this map uses the natural ordering
of its keys |
compute
public V compute (K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction)
Attempts to compute a mapping for the specified key and its current
mapped value (or null
if there is no current mapping). For
example, to either create or append a String
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.
Parameters | |
---|---|
key |
K : key with which the specified value is to be associated |
remappingFunction |
BiFunction : the remapping function to compute a value |
Returns | |
---|---|
V |
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 |
computeIfAbsent
public V computeIfAbsent (K key, Function<? super K, ? extends V> mappingFunction)
If the specified key is not already associated with a value (or is mapped
to null
), attempts to compute its value using the given mapping
function and enters it into this map unless null
.
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.
Parameters | |
---|---|
key |
K : key with which the specified value is to be associated |
mappingFunction |
Function : the mapping function to compute a value |
Returns | |
---|---|
V |
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
public V 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.
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.
Parameters | |
---|---|
key |
K : key with which the specified value is to be associated |
remappingFunction |
BiFunction : the remapping function to compute a value |
Returns | |
---|---|
V |
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 |
containsKey
public boolean containsKey (Object key)
Returns true
if this map contains a mapping for the specified
key.
Parameters | |
---|---|
key |
Object : key whose presence in this map is to be tested |
Returns | |
---|---|
boolean |
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 map |
NullPointerException |
if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys |
containsValue
public boolean containsValue (Object value)
Returns true
if this map maps one or more keys to the
specified value. More formally, returns true
if and only if
this map contains at least one mapping to a value v
such
that (value==null ? v==null : value.equals(v))
. This
operation will probably require time linear in the map size for
most implementations.
Parameters | |
---|---|
value |
Object : value whose presence in this map is to be tested |
Returns | |
---|---|
boolean |
true if a mapping to value exists;
false otherwise |
descendingKeySet
public NavigableSet<K> 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.
Returns | |
---|---|
NavigableSet<K> |
a reverse order navigable set view of the keys in this map |
descendingMap
public NavigableMap<K, V> 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
.
Returns | |
---|---|
NavigableMap<K, V> |
a reverse order view of this map |
entrySet
public Set<Entry<K, V>> entrySet ()
Returns a Set
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
and
Spliterator#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 the
setValue
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 the Iterator.remove
,
Set.remove
, removeAll
, retainAll
and
clear
operations. It does not support the
add
or addAll
operations.
Returns | |
---|---|
Set<Entry<K, V>> |
a set view of the mappings contained in this map |
firstEntry
public Entry<K, V> firstEntry ()
Returns a key-value mapping associated with the least
key in this map, or null
if the map is empty.
Returns | |
---|---|
Entry<K, V> |
an entry with the least key,
or null if this map is empty |
firstKey
public K firstKey ()
Returns the first (lowest) key currently in this map.
Returns | |
---|---|
K |
the first (lowest) key currently in this map |
Throws | |
---|---|
NoSuchElementException |
floorEntry
public Entry<K, V> 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.
Parameters | |
---|---|
key |
K : the key |
Returns | |
---|---|
Entry<K, V> |
an entry with the greatest key less than or equal to
key , or null if there is no such key |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys |
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.
Parameters | |
---|---|
key |
K : the key |
Returns | |
---|---|
K |
the greatest key less than or equal to key ,
or null if there is no such key |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys |
forEach
public void forEach (BiConsumer<? super K, ? super V> action)
Performs the given action for each entry in this map until all entries have been processed or the action throws an exception. Unless otherwise specified by the implementing class, actions are performed in the order of entry set iteration (if an iteration order is specified.) Exceptions thrown by the action are relayed to the caller.
Parameters | |
---|---|
action |
BiConsumer : The action to be performed for each entry |
get
public V get (Object key)
Returns the value to which the specified key is mapped,
or null
if this map contains no mapping for the key.
More formally, if this map contains a mapping from a key
k
to a value v
such that key
compares
equal to k
according to the map's ordering, then this
method returns v
; otherwise it returns null
.
(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 to null
.
The containsKey
operation may be used to
distinguish these two cases.
Parameters | |
---|---|
key |
Object : the key whose associated value is to be returned |
Returns | |
---|---|
V |
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 map |
NullPointerException |
if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys |
headMap
public SortedMap<K, V> headMap (K toKey)
Returns a view of the portion of this map whose keys are
strictly less than 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.
Equivalent to headMap(toKey, false)
.
Parameters | |
---|---|
toKey |
K : high endpoint (exclusive) of the keys in the returned map |
Returns | |
---|---|
SortedMap<K, V> |
a view of the portion of this map whose keys are strictly
less than toKey |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if toKey is null
and this map uses natural ordering, or its comparator
does not permit null keys |
IllegalArgumentException |
headMap
public NavigableMap<K, V> 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.
Parameters | |
---|---|
toKey |
K : high endpoint of the keys in the returned map |
inclusive |
boolean : true if the high endpoint
is to be included in the returned view |
Returns | |
---|---|
NavigableMap<K, V> |
a view of the portion of this map whose keys are less than
(or equal to, if inclusive is true) toKey |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if toKey is null
and this map uses natural ordering, or its comparator
does not permit null keys |
IllegalArgumentException |
higherEntry
public Entry<K, V> 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.
Parameters | |
---|---|
key |
K : the key |
Returns | |
---|---|
Entry<K, V> |
an entry with the least key greater than key ,
or null if there is no such key |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys |
higherKey
public K higherKey (K key)
Returns the least key strictly greater than the given key, or
null
if there is no such key.
Parameters | |
---|---|
key |
K : the key |
Returns | |
---|---|
K |
the least key greater than key ,
or null if there is no such key |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys |
keySet
public Set<K> keySet ()
Returns a Set
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
and Spliterator#ORDERED
with an encounter order that is ascending
key order. The spliterator's comparator (see
Spliterator.getComparator()
) is null
if
the tree map's comparator (see comparator()
) is null
.
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 the
Iterator.remove
, Set.remove
,
removeAll
, retainAll
, and clear
operations. It does not support the add
or addAll
operations.
Returns | |
---|---|
Set<K> |
a set view of the keys contained in this map |
lastEntry
public Entry<K, V> lastEntry ()
Returns a key-value mapping associated with the greatest
key in this map, or null
if the map is empty.
Returns | |
---|---|
Entry<K, V> |
an entry with the greatest key,
or null if this map is empty |
lastKey
public K lastKey ()
Returns the last (highest) key currently in this map.
Returns | |
---|---|
K |
the last (highest) key currently in this map |
Throws | |
---|---|
NoSuchElementException |
lowerEntry
public Entry<K, V> 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.
Parameters | |
---|---|
key |
K : the key |
Returns | |
---|---|
Entry<K, V> |
an entry with the greatest key less than key ,
or null if there is no such key |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys |
lowerKey
public K lowerKey (K key)
Returns the greatest key strictly less than the given key, or
null
if there is no such key.
Parameters | |
---|---|
key |
K : the key |
Returns | |
---|---|
K |
the greatest key less than key ,
or null if there is no such key |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys |
merge
public V merge (K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction)
If the specified key is not already associated with a value or is
associated with null, associates it with the given non-null value.
Otherwise, replaces the associated value with the results of the given
remapping function, or removes if the result is null
. This
method may be of use when combining multiple mapped values for a key.
For example, to either create or append a String 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.
Parameters | |
---|---|
key |
K : key with which the resulting value is to be associated |
value |
V : 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 key |
remappingFunction |
BiFunction : the remapping function to recompute a value if
present |
Returns | |
---|---|
V |
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 |
navigableKeySet
public NavigableSet<K> 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.
Returns | |
---|---|
NavigableSet<K> |
a navigable set view of the keys in this map |
pollFirstEntry
public Entry<K, V> pollFirstEntry ()
Removes and returns a key-value mapping associated with
the least key in this map, or null
if the map is empty.
Returns | |
---|---|
Entry<K, V> |
the removed first entry of this map,
or null if this map is empty |
pollLastEntry
public Entry<K, V> pollLastEntry ()
Removes and returns a key-value mapping associated with
the greatest key in this map, or null
if the map is empty.
Returns | |
---|---|
Entry<K, V> |
the removed last entry of this map,
or null if this map is empty |
put
public V put (K key, V value)
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.
Parameters | |
---|---|
key |
K : key with which the specified value is to be associated |
value |
V : value to be associated with the specified key |
Returns | |
---|---|
V |
the previous value associated with key , or
null if there was no mapping for key .
(A null return can also indicate that the map
previously associated null with key .) |
Throws | |
---|---|
ClassCastException |
if the specified key cannot be compared with the keys currently in the map |
NullPointerException |
if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys |
putAll
public void putAll (Map<? extends K, ? extends V> map)
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.
Parameters | |
---|---|
map |
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 map |
NullPointerException |
if the specified map is null or the specified map contains a null key and this map does not permit null keys |
putFirst
public V putFirst (K k, V v)
Throws UnsupportedOperationException
. The encounter order induced by this
map's comparison method determines the position of mappings, so explicit positioning
is not supported.
Parameters | |
---|---|
k |
K : the key |
v |
V : the value |
Returns | |
---|---|
V |
the value previously associated with k, or null if none |
Throws | |
---|---|
UnsupportedOperationException |
always |
putIfAbsent
public V putIfAbsent (K key, V value)
If the specified key is not already associated with a value (or is mapped
to null
) associates it with the given value and returns
null
, else returns the current value.
Parameters | |
---|---|
key |
K : key with which the specified value is to be associated |
value |
V : value to be associated with the specified key |
Returns | |
---|---|
V |
the previous value associated with the specified key, or
null if there was no mapping for the key.
(A null return can also indicate that the map
previously associated null with the key,
if the implementation supports null values.) |
putLast
public V putLast (K k, V v)
Throws UnsupportedOperationException
. The encounter order induced by this
map's comparison method determines the position of mappings, so explicit positioning
is not supported.
Parameters | |
---|---|
k |
K : the key |
v |
V : the value |
Returns | |
---|---|
V |
the value previously associated with k, or null if none |
Throws | |
---|---|
UnsupportedOperationException |
always |
remove
public V remove (Object key)
Removes the mapping for this key from this TreeMap if present.
Parameters | |
---|---|
key |
Object : key for which mapping should be removed |
Returns | |
---|---|
V |
the previous value associated with key , or
null if there was no mapping for key .
(A null return can also indicate that the map
previously associated null with key .) |
Throws | |
---|---|
ClassCastException |
if the specified key cannot be compared with the keys currently in the map |
NullPointerException |
if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys |
replace
public boolean replace (K key, V oldValue, V newValue)
Replaces the entry for the specified key only if currently mapped to the specified value.
Parameters | |
---|---|
key |
K : key with which the specified value is associated |
oldValue |
V : value expected to be associated with the specified key |
newValue |
V : value to be associated with the specified key |
Returns | |
---|---|
boolean |
true if the value was replaced |
replace
public V replace (K key, V value)
Replaces the entry for the specified key only if it is currently mapped to some value.
Parameters | |
---|---|
key |
K : key with which the specified value is associated |
value |
V : value to be associated with the specified key |
Returns | |
---|---|
V |
the previous value associated with the specified key, or
null if there was no mapping for the key.
(A null return can also indicate that the map
previously associated null with the key,
if the implementation supports null values.) |
replaceAll
public void replaceAll (BiFunction<? super K, ? super V, ? extends V> function)
Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception. Exceptions thrown by the function are relayed to the caller.
Parameters | |
---|---|
function |
BiFunction : the function to apply to each entry |
size
public int size ()
Returns the number of key-value mappings in this map.
Returns | |
---|---|
int |
the number of key-value mappings in this map |
subMap
public SortedMap<K, V> subMap (K fromKey, K toKey)
Returns a view of the portion of this map whose keys range from
fromKey
, inclusive, to toKey
, exclusive. (If
fromKey
and toKey
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)
.
Parameters | |
---|---|
fromKey |
K : low endpoint (inclusive) of the keys in the returned map |
toKey |
K : high endpoint (exclusive) of the keys in the returned map |
Returns | |
---|---|
SortedMap<K, V> |
a view of the portion of this map whose keys range from
fromKey , inclusive, to toKey , exclusive |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if fromKey or toKey is
null and this map uses natural ordering, or its comparator
does not permit null keys |
IllegalArgumentException |
subMap
public NavigableMap<K, V> 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
fromInclusive
and toInclusive
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.
Parameters | |
---|---|
fromKey |
K : low endpoint of the keys in the returned map |
fromInclusive |
boolean : true if the low endpoint
is to be included in the returned view |
toKey |
K : high endpoint of the keys in the returned map |
toInclusive |
boolean : true if the high endpoint
is to be included in the returned view |
Returns | |
---|---|
NavigableMap<K, V> |
a view of the portion of this map whose keys range from
fromKey to toKey |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if fromKey or toKey is
null and this map uses natural ordering, or its comparator
does not permit null keys |
IllegalArgumentException |
tailMap
public NavigableMap<K, V> 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.
Parameters | |
---|---|
fromKey |
K : low endpoint of the keys in the returned map |
inclusive |
boolean : true if the low endpoint
is to be included in the returned view |
Returns | |
---|---|
NavigableMap<K, V> |
a view of the portion of this map whose keys are greater than
(or equal to, if inclusive is true) fromKey |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if fromKey is null
and this map uses natural ordering, or its comparator
does not permit null keys |
IllegalArgumentException |
tailMap
public SortedMap<K, V> tailMap (K fromKey)
Returns a view of the portion of this map whose keys are
greater than or equal to 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.
Equivalent to tailMap(fromKey, true)
.
Parameters | |
---|---|
fromKey |
K : low endpoint (inclusive) of the keys in the returned map |
Returns | |
---|---|
SortedMap<K, V> |
a view of the portion of this map whose keys are greater
than or equal to fromKey |
Throws | |
---|---|
ClassCastException |
|
NullPointerException |
if fromKey is null
and this map uses natural ordering, or its comparator
does not permit null keys |
IllegalArgumentException |
values
public Collection<V> values ()
Returns a Collection
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 the Iterator.remove
,
Collection.remove
, removeAll
,
retainAll
and clear
operations. It does not
support the add
or addAll
operations.
Returns | |
---|---|
Collection<V> |
a collection view of the values contained in this map |