Class TreeMap<K,V>
- java.lang.Object
-
- java.util.AbstractMap<K,V>
-
- java.util.TreeMap<K,V>
- Type Parameters:
-
K
- the type of keys maintained by this map -
V
- the type of mapped values
- All Implemented Interfaces:
-
Serializable
,Cloneable
,Map<K,V>
,NavigableMap<K,V>
,SortedMap<K,V>
public class TreeMap<K,V> extends AbstractMap<K,V> implements NavigableMap<K,V>, Cloneable, Serializable
A Red-Black tree based 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.
All Map.Entry
pairs returned by methods in this class and its views represent snapshots of mappings at the time they were produced. They do not support the Entry.setValue
method. (Note however that it is possible to change mappings in the associated map using put
.)
This class is a member of the Java Collections Framework.
- Since:
- 1.2
- See Also:
-
Map
,HashMap
,Hashtable
,Comparable
,Comparator
,Collection
, Serialized Form
Nested Class Summary
Nested classes/interfaces declared in class java.util.AbstractMap
AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>
Constructor Summary
Constructor | Description |
---|---|
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. |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
Map.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 |
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<Map.Entry<K,V>> | entrySet() | Returns a |
Map.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. |
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 |
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 |
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 |
Map.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 |
Map.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. |
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 |
NavigableSet<K> | navigableKeySet() | Returns a |
Map.Entry<K,V> | pollFirstEntry() | Removes and returns a key-value mapping associated with the least key in this map, or |
Map.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 | remove(Object key) | Removes the mapping for this key from this TreeMap if present. |
int | size() | Returns the number of key-value mappings in this map. |
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 |
SortedMap<K,V> | subMap(K fromKey,
K toKey) | Returns a view of the portion of this map whose keys range from |
SortedMap<K,V> | tailMap(K fromKey) | Returns a view of the portion of this map whose keys are greater than or equal to |
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 |
Collection<V> | values() | Returns a |
Methods declared in class java.util.AbstractMap
equals, hashCode, isEmpty, toString
Methods declared in class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait
Methods declared in interface java.util.Map
compute, computeIfAbsent, computeIfPresent, equals, forEach, getOrDefault, hashCode, isEmpty, merge, putIfAbsent, remove, replace, replace, replaceAll
Methods declared in interface java.util.SortedMap
comparator
Constructor Detail
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
- the comparator that will be used to order this map. Ifnull
, the natural 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
- the map whose mappings are to be placed in this map - Throws:
-
ClassCastException
- if the keys in m are notComparable
, 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
- 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 Detail
size
public int size()
Returns the number of key-value mappings in this map.
- Specified by:
-
size
in interfaceMap<K,V>
- Overrides:
-
size
in classAbstractMap<K,V>
- Returns:
- the number of key-value mappings in this map
containsKey
public boolean containsKey(Object key)
Returns true
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 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.
- 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
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.
- 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 map -
NullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys
firstKey
public K firstKey()
Description copied from interface: SortedMap
Returns the first (lowest) key currently in this map.
- Specified by:
-
firstKey
in interfaceSortedMap<K,V>
- Returns:
- the first (lowest) key currently in this map
- Throws:
-
NoSuchElementException
- if this map is empty
lastKey
public K lastKey()
Description copied from interface: SortedMap
Returns the last (highest) key currently in this map.
- Specified by:
-
lastKey
in interfaceSortedMap<K,V>
- Returns:
- the last (highest) key currently in this map
- Throws:
-
NoSuchElementException
- if this map is empty
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.
- 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 map -
NullPointerException
- if the specified map is null or the specified map contains a null key and this map does not permit null keys
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.
- Specified by:
-
put
in interfaceMap<K,V>
- Overrides:
-
put
in classAbstractMap<K,V>
- Parameters:
-
key
- key with which the specified value is to be associated -
value
- 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 map -
NullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys
remove
public V remove(Object key)
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 map -
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.)
- Overrides:
-
clone
in classAbstractMap<K,V>
- Returns:
- a shallow copy of this map
- See Also:
Cloneable
firstEntry
public Map.Entry<K,V> firstEntry()
Description copied from interface: NavigableMap
Returns a key-value mapping associated with the least key in this map, or null
if the map is empty.
- Specified by:
-
firstEntry
in interfaceNavigableMap<K,V>
- Returns:
- an entry with the least key, or
null
if this map is empty - Since:
- 1.6
lastEntry
public Map.Entry<K,V> lastEntry()
Description copied from interface: NavigableMap
Returns a key-value mapping associated with the greatest key in this map, or null
if the map is empty.
- Specified by:
-
lastEntry
in interfaceNavigableMap<K,V>
- Returns:
- an entry with the greatest key, or
null
if this map is empty - Since:
- 1.6
pollFirstEntry
public Map.Entry<K,V> pollFirstEntry()
Description copied from interface: NavigableMap
Removes and returns a key-value mapping associated with the least key in this map, or null
if the map is empty.
- Specified by:
-
pollFirstEntry
in interfaceNavigableMap<K,V>
- Returns:
- the removed first entry of this map, or
null
if this map is empty - Since:
- 1.6
pollLastEntry
public Map.Entry<K,V> pollLastEntry()
Description copied from interface: NavigableMap
Removes and returns a key-value mapping associated with the greatest key in this map, or null
if the map is empty.
- Specified by:
-
pollLastEntry
in interfaceNavigableMap<K,V>
- Returns:
- the removed last entry of this map, or
null
if this map is empty - Since:
- 1.6
lowerEntry
public Map.Entry<K,V> lowerEntry(K key)
Description copied from interface: NavigableMap
Returns a key-value mapping associated with the greatest key strictly less than the given key, or null
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 map -
NullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys - Since:
- 1.6
lowerKey
public K lowerKey(K key)
Description copied from interface: NavigableMap
Returns the greatest key strictly less than the given key, or null
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 map -
NullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys - Since:
- 1.6
floorEntry
public Map.Entry<K,V> floorEntry(K key)
Description copied from interface: NavigableMap
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.
- 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 map -
NullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys - Since:
- 1.6
floorKey
public K floorKey(K key)
Description copied from interface: NavigableMap
Returns the greatest key less than or equal to the given key, or null
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 map -
NullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys - Since:
- 1.6
ceilingEntry
public Map.Entry<K,V> ceilingEntry(K key)
Description copied from interface: NavigableMap
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.
- 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 map -
NullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys - Since:
- 1.6
ceilingKey
public K ceilingKey(K key)
Description copied from interface: NavigableMap
Returns the least key greater than or equal to the given key, or null
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 map -
NullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys - Since:
- 1.6
higherEntry
public Map.Entry<K,V> higherEntry(K key)
Description copied from interface: NavigableMap
Returns a key-value mapping associated with the least key strictly greater than the given key, or null
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 map -
NullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys - Since:
- 1.6
higherKey
public K higherKey(K key)
Description copied from interface: NavigableMap
Returns the least key strictly greater than the given key, or null
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 map -
NullPointerException
- if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys - Since:
- 1.6
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 SortedMap.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.
- Specified by:
-
keySet
in interfaceMap<K,V>
- Specified by:
-
keySet
in interfaceSortedMap<K,V>
- Overrides:
-
keySet
in classAbstractMap<K,V>
- Returns:
- a set view of the keys contained in this map
navigableKeySet
public NavigableSet<K> navigableKeySet()
Description copied from interface: NavigableMap
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.
- Specified by:
-
navigableKeySet
in interfaceNavigableMap<K,V>
- Returns:
- a navigable set view of the keys in this map
- Since:
- 1.6
descendingKeySet
public NavigableSet<K> descendingKeySet()
Description copied from interface: NavigableMap
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.
- Specified by:
-
descendingKeySet
in interfaceNavigableMap<K,V>
- Returns:
- a reverse order navigable set view of the keys in this map
- Since:
- 1.6
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.
- Specified by:
-
values
in interfaceMap<K,V>
- Specified by:
-
values
in interfaceSortedMap<K,V>
- Overrides:
-
values
in classAbstractMap<K,V>
- Returns:
- a collection view of the values contained in this map
entrySet
public Set<Map.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.
- Specified by:
-
entrySet
in interfaceMap<K,V>
- Specified by:
-
entrySet
in interfaceSortedMap<K,V>
- Returns:
- a set view of the mappings contained in this map, sorted in ascending key order
descendingMap
public NavigableMap<K,V> 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 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
.
- Specified by:
-
descendingMap
in interfaceNavigableMap<K,V>
- Returns:
- a reverse order view of this map
- Since:
- 1.6
subMap
public NavigableMap<K,V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive)
Description copied from interface: NavigableMap
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.
- Specified by:
-
subMap
in interfaceNavigableMap<K,V>
- Parameters:
-
fromKey
- low endpoint of the keys in the returned map -
fromInclusive
-true
if the low endpoint is to be included in the returned view -
toKey
- high endpoint of the keys in the returned map -
toInclusive
-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 keys -
IllegalArgumentException
- 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
public NavigableMap<K,V> headMap(K toKey, boolean inclusive)
Description copied from interface: NavigableMap
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.
- Specified by:
-
headMap
in interfaceNavigableMap<K,V>
- Parameters:
-
toKey
- high endpoint of the keys in the returned map -
inclusive
-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 keys -
IllegalArgumentException
- if this map itself has a restricted range, andtoKey
lies outside the bounds of the range - Since:
- 1.6
tailMap
public NavigableMap<K,V> tailMap(K fromKey, boolean inclusive)
Description copied from interface: NavigableMap
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.
- Specified by:
-
tailMap
in interfaceNavigableMap<K,V>
- Parameters:
-
fromKey
- low endpoint of the keys in the returned map -
inclusive
-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 keys -
IllegalArgumentException
- if this map itself has a restricted range, andfromKey
lies outside the bounds of the range - Since:
- 1.6
subMap
public SortedMap<K,V> subMap(K fromKey, K toKey)
Description copied from interface: NavigableMap
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)
.
- 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 map -
toKey
- 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 keys -
IllegalArgumentException
- iffromKey
is greater thantoKey
; or if this map itself has a restricted range, andfromKey
ortoKey
lies outside the bounds of the range
headMap
public SortedMap<K,V> headMap(K toKey)
Description copied from interface: NavigableMap
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)
.
- 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 keys -
IllegalArgumentException
- if this map itself has a restricted range, andtoKey
lies outside the bounds of the range
tailMap
public SortedMap<K,V> tailMap(K fromKey)
Description copied from interface: NavigableMap
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)
.
- 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 keys -
IllegalArgumentException
- if this map itself has a restricted range, andfromKey
lies outside the bounds of the range