java.util.AbstractMap<K,V>
java.util.TreeMap<K,V>
is new.
java.lang.Object
public class TreeMap<K,V>
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 sorted map (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 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
Java Collections Framework
.
| Nested Class Summary |
|---|
| Nested classes/interfaces inherited from class java.util. AbstractMap |
|---|
| AbstractMap.SimpleEntry < K , V >, AbstractMap.SimpleImmutableEntry < K , V > |
| Constructor Summary | |
|---|---|
|
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 | |
|---|---|
| Map.Entry < K , V |
ceilingEntry
(
K
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. |
| K |
ceilingKey
(
K
Returns the least key greater than or equal to the given key, or null if there is no such key. |
| void |
clear
() Removes all of the mappings from this map. |
| Object |
clone
() Returns a shallow copy of this TreeMap instance. |
| 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. |
| boolean |
containsKey
(
Object
key) Returns true if this map contains a mapping for the specified key. |
| boolean |
containsValue
(
Object
value) Returns true if this map maps one or more keys to the specified value. |
|
NavigableSet
|
descendingKeySet
Returns a
reverse order
NavigableSet
|
|
NavigableMap
,
V
|
descendingMap
Returns a
reverse order view of the mappings contained in this map.
|
| Set < Map.Entry < K , V >> |
entrySet
() Returns a Set view of the mappings contained in this map. |
| Map.Entry < K , V |
firstEntry
() Returns a key-value mapping associated with the least key in this map, or null if the map is empty. |
| K |
firstKey
() Returns the first (lowest) key currently in this map. |
| Map.Entry < K , V |
floorEntry
(
K
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. |
| K |
floorKey
(
K
Returns the greatest key less than or equal to the given key, or null if there is no such key. |
| 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. |
| SortedMap < K , V |
headMap
(
K
Returns a view of the portion of this map whose keys are strictly less than
toKey
.
|
|
NavigableMap
|
headMap
Returns a
view of
portion of this map whose keys are less
(or equal to,
inclusive
true) toKey.
|
|
Map.Entry
<
K
,
V
|
higherEntry
Returns
a key-value mapping associated with
the least key strictly greater than the given key, or
null
if there is no such key. |
|
K
|
higherKey
(
K
Returns the least key strictly greater than the given key, or null if there is no such key.
|
| Set < K > |
keySet
() Returns a Set view of the keys contained in this map. |
| Map.Entry < K , V |
lastEntry
() Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty. |
| K |
lastKey
() Returns the last (highest) key currently in this map. |
| Map.Entry < K , V |
lowerEntry
(
K
Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key. |
| K |
lowerKey
(
K
Returns the greatest key strictly less than the given key, or null if there is no such key. |
|
NavigableSet
|
navigableKeySet
()
Returns a
NavigableSet
|
|
Map.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.
|
|
|
|
|
Map.Entry
|
pollLastEntry
()
Removes and returns
key-value mapping associated with
greatest key in
map,
null if the map is empty.
|
|
|
|
|
|
|
| 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
|
subMap
boolean fromInclusive,
K
Returns a view of the portion of this map whose keys range from fromKey
toKey.
|
| SortedMap < K , V |
subMap
fromKey,
K
Returns a view of the portion of this map whose keys range from
fromKey
, inclusive,
toKey
, exclusive.
|
|
SortedMap
<
K
,
V
|
tailMap
(
K
Returns a view of the portion of this map whose keys are greater than or equal to
fromKey
.
|
|
NavigableMap
<
K
,
V
|
tailMap
(
K
Returns a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) fromKey.
|
| Collection < V > |
values
() Returns a Collection view of the values contained in this map. |
| Methods inherited from class java.util. AbstractMap |
|---|
| equals , hashCode , isEmpty , toString |
| Methods inherited from class java.lang. Object |
|---|
| finalize , getClass , notify , notifyAll , wait , wait , wait |
| Methods inherited from interface java.util. Map |
|---|
| equals , hashCode , isEmpty |
| Constructor Detail |
|---|
public TreeMap()
public TreeMap(Comparator<? super K> comparator)
public TreeMap(Map<? extends K,? extends V> m)
public TreeMap(SortedMap<K,? extends V> m)
| Method Detail |
|---|
public int size()
public boolean containsKey(Object key)
public boolean containsValue(Object value)
public V get(Object 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.
public Comparator<? super K> comparator()
public K firstKey()
public K lastKey()
public void putAll(Map<? extends K,? extends V> map)
public V put(K key,
V value)
public V remove(Object key)
public void clear()
public Object clone()
public Map.Entry<K,V> firstEntry()
public Map.Entry<K,V> lastEntry()
public Map.Entry<K,V> pollFirstEntry()
public Map.Entry<K,V> pollLastEntry()
public Map.Entry<K,V> lowerEntry(K key)
key,
public K lowerKey(K key)
key,
public Map.Entry<K,V> floorEntry(K key)
key,
public K floorKey(K key)
key,
public Map.Entry<K,V> ceilingEntry(K key)
key,
public K ceilingKey(K key)
key,
public Map.Entry<K,V> higherEntry(K key)
key,
public K higherKey(K key)
key,
public Set<K> keySet()
navigableKeySet
publicCollection<V>values()
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 interface
NavigableMap
navigable set
keys
Since:
1.6
descendingKeySet
publicSet<Map.Entry<K,V>>entrySet()
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.
descendingKeySet
in interface
NavigableMap
reverse order navigable
set view of the
keys
Since:
1.6
values
publicSet<Map.Entry<K,V>>descendingEntrySet()
Returns a
Collection
values
collection's
values
ascending order of the corresponding keys.
collection
collection,
collection
operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the
Collection.remove
values
Map
Specified by:
values
in interface
SortedMap
<
K
,
V
>
Overrides:
values
in class
AbstractMap
<
K
,
V
>
Returns:
a collection view of the values contained in this map
entrySet
public Set>descendingKeySet()
mappings
entries
ascending key
operation, or through the
setValue
operation on a map entry returned by the iterator) the results of the iteration are undefined.
entrySet
Map
Specified by:
entrySet
in interface
SortedMap
<
K
,
V
>
Specified by:
entrySet
in class
AbstractMap
<
K
,
V
>
Returns:
a set view of the mappings contained in this map
descendingMap
public NavigableMap<K,V>navigableSubMap(KfromKey,KtoKey)
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
will throw
an
ordering equivalent to
Collections.reverseOrder
(comparator())
IllegalArgumentException
. The expression m.descendingMap().descendingMap() returns a view of m essentially equivalent to m.
on an attempt to insert a key outside its range.
descendingMap
a reverse order view of this map
subMap
public NavigableMap<K,V>navigableHeadMap(KtoKey)
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 fromExclusive and toExclusive are both true.
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.
subMap
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
range from fromKey to
fromKey and
toKey
cannot be compared to one another using
using natural ordering).
fromKey or
toKey
cannot be compared to keys currently in the map.
fromKey
or
toKey
is null and this map uses natural ordering, or its comparator does not permit null keys
fromKey is greater than toKey; or if
this map itself has a restricted range, and
fromKey or
toKey
lies outside the bounds of the range
headMap
public NavigableMap<K,V>navigableTailMap(KfromKey)
NavigableMap
less
(or
to, if inclusive is true) toKey.
The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.
headMap
toKey - high endpoint of the keys in the returned map
inclusive - true if the high endpoint is to be included in the returned view
less
(or
to, if inclusive is true) toKey
toKey
toKey
toKey
toKey
toKey
tailMap
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 interface
NavigableMap
<
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
- if fromKey is not compatible with this map's comparator (or, if the map has no comparator, if fromKey does not implement
Comparable
). Implementations may, but are not required to, throw this exception if fromKey cannot be compared to keys currently in the map.
NullPointerException
- if
fromKey
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, and fromKey lies outside the bounds of the range
Since:
1.6
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).
subMap
in interface
NavigableMap
<
K
,
V
>
Specified by:
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).
headMap
in interface
NavigableMap
<
K
,
V
>
Specified by:
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).
tailMap
in interface
NavigableMap
<
K
,
V
>
Specified by: