Class TreeMap<K,V>
- 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:
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Nested Class Summary
Nested classes/interfaces declared in class java.util.AbstractMap
AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K, V> -
Constructor Summary
ConstructorsConstructorDescriptionTreeMap()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, ornullif there is no such key.ceilingKey(K key) Returns the least key greater than or equal to the given key, ornullif there is no such key.voidclear()Removes all of the mappings from this map.clone()Returns a shallow copy of thisTreeMapinstance.Comparator<? super K> Returns the comparator used to order the keys in this map, ornullif this map uses the natural ordering of its keys.Attempts to compute a mapping for the specified key and its current mapped value, ornullif 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).booleancontainsKey(Object key) Returnstrueif this map contains a mapping for the specified key.booleancontainsValue(Object value) Returnstrueif this map maps one or more keys to the specified value.Returns a reverse orderNavigableSetview of the keys contained in this map.Returns a reverse order view of the mappings contained in this map.entrySet()Returns aSetview of the mappings contained in this map.Returns a key-value mapping associated with the least key in this map, ornullif 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, ornullif there is no such key.Returns the greatest key less than or equal to the given key, ornullif there is no such key.Returns the value to which the specified key is mapped, ornullif 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, ifinclusiveis true)toKey.higherEntry(K key) Returns a key-value mapping associated with the least key strictly greater than the given key, ornullif there is no such key.Returns the least key strictly greater than the given key, ornullif there is no such key.keySet()Returns aSetview of the keys contained in this map.Returns a key-value mapping associated with the greatest key in this map, ornullif 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, ornullif there is no such key.Returns the greatest key strictly less than the given key, ornullif 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 aNavigableSetview of the keys contained in this map.Removes and returns a key-value mapping associated with the least key in this map, ornullif the map is empty (optional operation).Removes and returns a key-value mapping associated with the greatest key in this map, ornullif the map is empty (optional operation).Associates the specified value with the specified key in this map.voidCopies all of the mappings from the specified map to this map.ThrowsUnsupportedOperationException.ThrowsUnsupportedOperationException.Removes the mapping for this key from this TreeMap if present.intsize()Returns the number of key-value mappings in this map.Returns a view of the portion of this map whose keys range fromfromKeytotoKey.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, ifinclusiveis true)fromKey.values()Returns aCollectionview of the values contained in this map.Methods declared in class java.util.AbstractMap
equals, hashCode, isEmpty, toStringMethods declared in interface java.util.Map
equals, forEach, getOrDefault, hashCode, isEmpty, putIfAbsent, remove, replace, replace, replaceAllMethods declared in interface java.util.NavigableMap
reversedMethods declared in interface java.util.SequencedMap
sequencedEntrySet, sequencedKeySet, sequencedValues
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Constructor Details
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TreeMap
public TreeMap()Constructs a new, empty tree map, using the natural ordering of its keys. All keys inserted into the map must implement theComparableinterface. Furthermore, all such keys must be mutually comparable:k1.compareTo(k2)must not throw aClassCastExceptionfor any keysk1andk2in 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 aClassCastExceptionfor any keysk1andk2in 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.
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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 theComparableinterface. Furthermore, all such keys must be mutually comparable:k1.compareTo(k2)must not throw aClassCastExceptionfor any keysk1andk2in 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
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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
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Method Details
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size
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containsKey
Returnstrueif this map contains a mapping for the specified key.- Specified by:
containsKeyin interfaceMap<K,V> - Overrides:
containsKeyin classAbstractMap<K,V> - Parameters:
key- key whose presence in this map is to be tested- Returns:
trueif 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
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containsValue
Returnstrueif this map maps one or more keys to the specified value. More formally, returnstrueif and only if this map contains at least one mapping to a valuevsuch that(value==null ? v==null : value.equals(v)). This operation will probably require time linear in the map size for most implementations.- Specified by:
containsValuein interfaceMap<K,V> - Overrides:
containsValuein classAbstractMap<K,V> - Parameters:
value- value whose presence in this map is to be tested- Returns:
trueif a mapping tovalueexists;falseotherwise- Since:
- 1.2
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get
Returns the value to which the specified key is mapped, ornullif this map contains no mapping for the key.More formally, if this map contains a mapping from a key
kto a valuevsuch thatkeycompares equal tokaccording to the map's ordering, then this method returnsv; otherwise it returnsnull. (There can be at most one such mapping.)A return value of
nulldoes not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key tonull. ThecontainsKeyoperation may be used to distinguish these two cases.- Specified by:
getin interfaceMap<K,V> - Overrides:
getin 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
nullif 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
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comparator
Description copied from interface:SortedMapReturns the comparator used to order the keys in this map, ornullif this map uses the natural ordering of its keys.- Specified by:
comparatorin interfaceSortedMap<K,V> - Returns:
- the comparator used to order the keys in this map,
or
nullif this map uses the natural ordering of its keys
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firstKey
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lastKey
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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:
putFirstin interfaceSequencedMap<K,V> - Specified by:
putFirstin 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
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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:
putLastin interfaceSequencedMap<K,V> - Specified by:
putLastin 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
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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:
putAllin interfaceMap<K,V> - Overrides:
putAllin 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
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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:
putin interfaceMap<K,V> - Overrides:
putin 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, ornullif there was no mapping forkey. (Anullreturn can also indicate that the map previously associatednullwithkey.) - 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
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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
ConcurrentModificationExceptionif it is detected that the mapping function modifies this map during computation.- Specified by:
computeIfAbsentin 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
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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
ConcurrentModificationExceptionif it is detected that the remapping function modifies this map during computation.- Specified by:
computeIfPresentin 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
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compute
Attempts to compute a mapping for the specified key and its current mapped value, ornullif there is no current mapping (optional operation). For example, to either create or append aStringmsg to a value mapping:
(Methodmap.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
ConcurrentModificationExceptionif it is detected that the remapping function modifies this map during computation.- Specified by:
computein 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
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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 msgto 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
ConcurrentModificationExceptionif it is detected that the remapping function modifies this map during computation.- Specified by:
mergein 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
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remove
Removes the mapping for this key from this TreeMap if present.- Specified by:
removein interfaceMap<K,V> - Overrides:
removein classAbstractMap<K,V> - Parameters:
key- key for which mapping should be removed- Returns:
- the previous value associated with
key, ornullif there was no mapping forkey. (Anullreturn can also indicate that the map previously associatednullwithkey.) - 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
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clear
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clone
Returns a shallow copy of thisTreeMapinstance. (The keys and values themselves are not cloned.)- Overrides:
clonein classAbstractMap<K,V> - Returns:
- a shallow copy of this map
- See Also:
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firstEntry
Description copied from interface:NavigableMapReturns a key-value mapping associated with the least key in this map, ornullif the map is empty.- Specified by:
firstEntryin interfaceNavigableMap<K,V> - Specified by:
firstEntryin interfaceSequencedMap<K,V> - Returns:
- an entry with the least key,
or
nullif this map is empty - Since:
- 1.6
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lastEntry
Description copied from interface:NavigableMapReturns a key-value mapping associated with the greatest key in this map, ornullif the map is empty.- Specified by:
lastEntryin interfaceNavigableMap<K,V> - Specified by:
lastEntryin interfaceSequencedMap<K,V> - Returns:
- an entry with the greatest key,
or
nullif this map is empty - Since:
- 1.6
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pollFirstEntry
Description copied from interface:NavigableMapRemoves and returns a key-value mapping associated with the least key in this map, ornullif the map is empty (optional operation).- Specified by:
pollFirstEntryin interfaceNavigableMap<K,V> - Specified by:
pollFirstEntryin interfaceSequencedMap<K,V> - Returns:
- the removed first entry of this map,
or
nullif this map is empty - Since:
- 1.6
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pollLastEntry
Description copied from interface:NavigableMapRemoves and returns a key-value mapping associated with the greatest key in this map, ornullif the map is empty (optional operation).- Specified by:
pollLastEntryin interfaceNavigableMap<K,V> - Specified by:
pollLastEntryin interfaceSequencedMap<K,V> - Returns:
- the removed last entry of this map,
or
nullif this map is empty - Since:
- 1.6
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lowerEntry
Description copied from interface:NavigableMapReturns a key-value mapping associated with the greatest key strictly less than the given key, ornullif there is no such key.- Specified by:
lowerEntryin interfaceNavigableMap<K,V> - Parameters:
key- the key- Returns:
- an entry with the greatest key less than
key, ornullif 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
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lowerKey
Description copied from interface:NavigableMapReturns the greatest key strictly less than the given key, ornullif there is no such key.- Specified by:
lowerKeyin interfaceNavigableMap<K,V> - Parameters:
key- the key- Returns:
- the greatest key less than
key, ornullif 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
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floorEntry
Description copied from interface:NavigableMapReturns a key-value mapping associated with the greatest key less than or equal to the given key, ornullif there is no such key.- Specified by:
floorEntryin interfaceNavigableMap<K,V> - Parameters:
key- the key- Returns:
- an entry with the greatest key less than or equal to
key, ornullif 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
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floorKey
Description copied from interface:NavigableMapReturns the greatest key less than or equal to the given key, ornullif there is no such key.- Specified by:
floorKeyin interfaceNavigableMap<K,V> - Parameters:
key- the key- Returns:
- the greatest key less than or equal to
key, ornullif 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
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ceilingEntry
Description copied from interface:NavigableMapReturns a key-value mapping associated with the least key greater than or equal to the given key, ornullif there is no such key.- Specified by:
ceilingEntryin interfaceNavigableMap<K,V> - Parameters:
key- the key- Returns:
- an entry with the least key greater than or equal to
key, ornullif 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
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ceilingKey
Description copied from interface:NavigableMapReturns the least key greater than or equal to the given key, ornullif there is no such key.- Specified by:
ceilingKeyin interfaceNavigableMap<K,V> - Parameters:
key- the key- Returns:
- the least key greater than or equal to
key, ornullif 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
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higherEntry
Description copied from interface:NavigableMapReturns a key-value mapping associated with the least key strictly greater than the given key, ornullif there is no such key.- Specified by:
higherEntryin interfaceNavigableMap<K,V> - Parameters:
key- the key- Returns:
- an entry with the least key greater than
key, ornullif 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
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higherKey
Description copied from interface:NavigableMapReturns the least key strictly greater than the given key, ornullif there is no such key.- Specified by:
higherKeyin interfaceNavigableMap<K,V> - Parameters:
key- the key- Returns:
- the least key greater than
key, ornullif 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
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keySet
Returns aSetview 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.SORTEDandSpliterator.ORDEREDwith an encounter order that is ascending key order. The spliterator's comparator (seeSpliterator.getComparator()) isnullif 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
removeoperation), 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, andclearoperations. It does not support theaddoraddAlloperations. -
descendingKeySet
Description copied from interface:NavigableMapReturns a reverse orderNavigableSetview 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 ownremoveoperation), 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, andclearoperations. It does not support theaddoraddAlloperations.- Specified by:
descendingKeySetin interfaceNavigableMap<K,V> - Returns:
- a reverse order navigable set view of the keys in this map
- Since:
- 1.6
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values
Returns aCollectionview 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.ORDEREDwith 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
removeoperation), 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,retainAllandclearoperations. It does not support theaddoraddAlloperations. -
entrySet
Returns aSetview 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.SORTEDandSpliterator.ORDEREDwith 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
removeoperation, or through thesetValueoperation 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,retainAllandclearoperations. It does not support theaddoraddAlloperations. -
descendingMap
Description copied from interface:NavigableMapReturns 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 ownremoveoperation), 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 ofmessentially equivalent tom.- Specified by:
descendingMapin interfaceNavigableMap<K,V> - Returns:
- a reverse order view of this map
- Since:
- 1.6
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subMap
Description copied from interface:NavigableMapReturns a view of the portion of this map whose keys range fromfromKeytotoKey. IffromKeyandtoKeyare equal, the returned map is empty unlessfromInclusiveandtoInclusiveare 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
IllegalArgumentExceptionon 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:
subMapin interfaceNavigableMap<K,V> - Parameters:
fromKey- low endpoint of the keys in the returned mapfromInclusive-trueif the low endpoint is to be included in the returned viewtoKey- high endpoint of the keys in the returned maptoInclusive-trueif the high endpoint is to be included in the returned view- Returns:
- a view of the portion of this map whose keys range from
fromKeytotoKey - Throws:
ClassCastException- iffromKeyandtoKeycannot 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 iffromKeyortoKeycannot be compared to keys currently in the map.NullPointerException- iffromKeyortoKeyis null and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException- iffromKeyis greater thantoKey; or if this map itself has a restricted range, andfromKeyortoKeylies outside the bounds of the range- Since:
- 1.6
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headMap
Description copied from interface:NavigableMapReturns a view of the portion of this map whose keys are less than (or equal to, ifinclusiveis 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
IllegalArgumentExceptionon an attempt to insert a key outside its range.- Specified by:
headMapin interfaceNavigableMap<K,V> - Parameters:
toKey- high endpoint of the keys in the returned mapinclusive-trueif 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
inclusiveis true)toKey - Throws:
ClassCastException- iftoKeyis not compatible with this map's comparator (or, if the map has no comparator, iftoKeydoes not implementComparable). Implementations may, but are not required to, throw this exception iftoKeycannot be compared to keys currently in the map.NullPointerException- iftoKeyis null and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException- if this map itself has a restricted range, andtoKeylies outside the bounds of the range- Since:
- 1.6
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tailMap
Description copied from interface:NavigableMapReturns a view of the portion of this map whose keys are greater than (or equal to, ifinclusiveis 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
IllegalArgumentExceptionon an attempt to insert a key outside its range.- Specified by:
tailMapin interfaceNavigableMap<K,V> - Parameters:
fromKey- low endpoint of the keys in the returned mapinclusive-trueif 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
inclusiveis true)fromKey - Throws:
ClassCastException- iffromKeyis not compatible with this map's comparator (or, if the map has no comparator, iffromKeydoes not implementComparable). Implementations may, but are not required to, throw this exception iffromKeycannot be compared to keys currently in the map.NullPointerException- iffromKeyis null and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException- if this map itself has a restricted range, andfromKeylies outside the bounds of the range- Since:
- 1.6
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subMap
Description copied from interface:NavigableMapReturns a view of the portion of this map whose keys range fromfromKey, inclusive, totoKey, exclusive. (IffromKeyandtoKeyare 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
IllegalArgumentExceptionon an attempt to insert a key outside its range.Equivalent to
subMap(fromKey, true, toKey, false).- Specified by:
subMapin interfaceNavigableMap<K,V> - Specified by:
subMapin 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- iffromKeyandtoKeycannot 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 iffromKeyortoKeycannot be compared to keys currently in the map.NullPointerException- iffromKeyortoKeyis null and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException- iffromKeyis greater thantoKey; or if this map itself has a restricted range, andfromKeyortoKeylies outside the bounds of the range
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headMap
Description copied from interface:NavigableMapReturns 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
IllegalArgumentExceptionon an attempt to insert a key outside its range.Equivalent to
headMap(toKey, false).- Specified by:
headMapin interfaceNavigableMap<K,V> - Specified by:
headMapin 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- iftoKeyis not compatible with this map's comparator (or, if the map has no comparator, iftoKeydoes not implementComparable). Implementations may, but are not required to, throw this exception iftoKeycannot be compared to keys currently in the map.NullPointerException- iftoKeyis null and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException- if this map itself has a restricted range, andtoKeylies outside the bounds of the range
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tailMap
Description copied from interface:NavigableMapReturns 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
IllegalArgumentExceptionon an attempt to insert a key outside its range.Equivalent to
tailMap(fromKey, true).- Specified by:
tailMapin interfaceNavigableMap<K,V> - Specified by:
tailMapin 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- iffromKeyis not compatible with this map's comparator (or, if the map has no comparator, iffromKeydoes not implementComparable). Implementations may, but are not required to, throw this exception iffromKeycannot be compared to keys currently in the map.NullPointerException- iffromKeyis null and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException- if this map itself has a restricted range, andfromKeylies outside the bounds of the range
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