java.util

Class TreeMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

java.util.TreeMap<K,V>

Type Parameters:

K - type of key

V - type of value

All Implemented Interfaces:

Map<K,V>, NavigableMap<K,V>, SortedMap<K,V>

public class TreeMap<K,V>
extends AbstractMap<K,V>
implements NavigableMap<K,V>

TreeMap is an implementation of SortedMap. All optional operations (adding and removing) are supported. The values can be any objects. The keys can be any objects which are comparable to each other either using their natural

Since:

1.2

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Constructor Summary

Constructors

Constructor and Description
TreeMap() Constructs a new empty TreeMap instance.
TreeMap(Comparator<? super K> comparator) Constructs a new empty TreeMap instance with the specified comparator.
TreeMap(Map<? extends K,? extends V> map) Constructs a new TreeMap instance containing the mappings from the specified map and using natural ordering.
TreeMap(SortedMap<K,? extends V> map) Constructs a new TreeMap instance containing the mappings from the specified SortedMap and using the same comparator.

Method Summary

Modifier and Type	Method and Description
Map.Entry<K,V>	ceilingEntry(K key) Answers an entry related with the smallest key greater than or equal to the specified key, or null if no such key.
K	ceilingKey(K key) Answers the smallest key greater than or equal to the specified key, or null if no such key.
void	clear() Removes all mappings from this TreeMap, leaving it empty.
Comparator<? super K>	comparator() Returns the comparator used to compare elements in this map.
boolean	containsKey(Object key) Returns whether this map contains the specified key.
boolean	containsValue(Object value) Returns whether this map contains the specified value.
NavigableSet<K>	descendingKeySet() Answers a NavigableSet view of the keys in descending order.
NavigableMap<K,V>	descendingMap() Answers a reverse order view of the map.
Set<Map.Entry<K,V>>	entrySet() Returns a set containing all of the mappings in this map.
Map.Entry<K,V>	firstEntry() Answers the entry with the smallest key, or null if the map is empty.
K	firstKey() Returns the first key in this map.
Map.Entry<K,V>	floorEntry(K key) Answers an entry related with the biggest key less than or equal to the specified key, or null if no such key.
K	floorKey(K key) Answers the biggest key less than or equal to the specified key, or null if no such key.
V	get(Object key) Returns the value of the mapping with the specified key.
SortedMap<K,V>	headMap(K endKey) Returns a sorted map over a range of this sorted map with all keys that are less than the specified endKey.
NavigableMap<K,V>	headMap(K end, boolean inclusive) Answers a view of the head of the map whose keys are smaller than (or equal to, depends on inclusive argument) endKey.
Map.Entry<K,V>	higherEntry(K key) Answers an entry related with the smallest key greater than the specified key, or null if no such key.
K	higherKey(K key) Answers the smallest key greater than the specified key, or null if no such key.
Set<K>	keySet() Returns a set of the keys contained in this map.
Map.Entry<K,V>	lastEntry() Answers the entry with the biggest key, or null if the map is empty.
K	lastKey() Returns the last key in this map.
Map.Entry<K,V>	lowerEntry(K key) Answers an entry related with the biggest key less than the specified key, or null if no such key.
K	lowerKey(K key) Answers the biggest key less than the specified key, or null if no such key.
NavigableSet<K>	navigableKeySet() Answers a NavigableSet view of the keys in ascending order.
Map.Entry<K,V>	pollFirstEntry() Deletes and answers the entry with the smallest key, or null if the map is empty.
Map.Entry<K,V>	pollLastEntry() Deletes and answers the entry with the biggest key, or null if the map is empty.
V	put(K key, V value) Maps the specified key to the specified value.
void	putAll(Map<? extends K,? extends V> map) Copies all the mappings in the given map to this map.
V	remove(Object key) Removes the mapping with the specified key from this map.
int	size() Returns the number of mappings in this map.
NavigableMap<K,V>	subMap(K start, boolean startInclusive, K end, boolean endInclusive) Answers a view of part of the map whose keys is from startKey to endKey.
SortedMap<K,V>	subMap(K startKey, K endKey) Returns a sorted map over a range of this sorted map with all keys greater than or equal to the specified startKey and less than the specified endKey.
SortedMap<K,V>	tailMap(K startKey) Returns a sorted map over a range of this sorted map with all keys that are greater than or equal to the specified startKey.
NavigableMap<K,V>	tailMap(K start, boolean inclusive) Answers a view of the tail of the map whose keys are bigger than (or equal to, depends on inclusive argument) startKey.
Collection<V>	values() Returns a collection 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

clone, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

equals, hashCode, isEmpty

Constructor Detail

TreeMap

public TreeMap()

Constructs a new empty TreeMap instance.

TreeMap

public TreeMap(Comparator<? super K> comparator)

Constructs a new empty TreeMap instance with the specified comparator.

Parameters:

comparator - the comparator to compare keys with.

TreeMap

public TreeMap(Map<? extends K,? extends V> map)

Constructs a new TreeMap instance containing the mappings from the specified map and using natural ordering.

Parameters:

map - the mappings to add.

Throws:

ClassCastException - if a key in the specified map does not implement the Comparable interface, or if the keys in the map cannot be compared.

TreeMap

public TreeMap(SortedMap<K,? extends V> map)

Constructs a new TreeMap instance containing the mappings from the specified SortedMap and using the same comparator.

Parameters:

map - the mappings to add.

Method Detail

clear

public void clear()

Removes all mappings from this TreeMap, leaving it empty.

Specified by:

clear in interface Map<K,V>

Overrides:

clear in class AbstractMap<K,V>

See Also:

Map.isEmpty(), size()

comparator

public Comparator<? super K> comparator()

Returns the comparator used to compare elements in this map.

Specified by:

comparator in interface SortedMap<K,V>

Returns:

the comparator or null if the natural ordering is used.

containsKey

public boolean containsKey(Object key)

Returns whether this map contains the specified key.

Specified by:

containsKey in interface Map<K,V>

Overrides:

containsKey in class AbstractMap<K,V>

Parameters:

key - the key to search for.

Returns:

true if this map contains the specified key, false otherwise.

Throws:

ClassCastException - if the specified key cannot be compared with the keys in this map.

NullPointerException - if the specified key is null and the comparator cannot handle null keys.

containsValue

public boolean containsValue(Object value)

Returns whether this map contains the specified value.

Specified by:

containsValue in interface Map<K,V>

Overrides:

containsValue in class AbstractMap<K,V>

Parameters:

value - the value to search for.

Returns:

true if this map contains the specified value, false otherwise.

firstKey

public K firstKey()

Returns the first key in this map.

Specified by:

firstKey in interface SortedMap<K,V>

Returns:

the first key in this map.

Throws:

NoSuchElementException - if this map is empty.

get

public V get(Object key)

Returns the value of the mapping with the specified key.

Specified by:

get in interface Map<K,V>

Overrides:

get in class AbstractMap<K,V>

Parameters:

key - the key.

Returns:

the value of the mapping with the specified key.

Throws:

ClassCastException - if the key cannot be compared with the keys in this map.

NullPointerException - if the key is null and the comparator cannot handle null.

keySet

public Set<K> keySet()

Returns a set of the keys contained in this map. The set is backed by this map so changes to one are reflected by the other. The set does not support adding.

Specified by:

keySet in interface Map<K,V>

Overrides:

keySet in class AbstractMap<K,V>

Returns:

a set of the keys.

lastKey

public K lastKey()

Returns the last key in this map.

Specified by:

lastKey in interface SortedMap<K,V>

Returns:

the last key in this map.

Throws:

NoSuchElementException - if this map is empty.

put

public V put(K key,
             V value)

Maps the specified key to the specified value.

Specified by:

put in interface Map<K,V>

Overrides:

put in class AbstractMap<K,V>

Parameters:

key - the key.

value - the value.

Returns:

the value of any previous mapping with the specified key or null if there was no mapping.

Throws:

ClassCastException - if the specified key cannot be compared with the keys in this map.

NullPointerException - if the specified key is null and the comparator cannot handle null keys.

putAll

public void putAll(Map<? extends K,? extends V> map)

Copies all the mappings in the given map to this map. These mappings will replace all mappings that this map had for any of the keys currently in the given map.

Specified by:

putAll in interface Map<K,V>

Overrides:

putAll in class AbstractMap<K,V>

Parameters:

map - the map to copy mappings from.

Throws:

ClassCastException - if a key in the specified map cannot be compared with the keys in this map.

NullPointerException - if a key in the specified map is null and the comparator cannot handle null keys.

remove

public V remove(Object key)

Removes the mapping with the specified key from this map.

Specified by:

remove in interface Map<K,V>

Overrides:

remove in class AbstractMap<K,V>

Parameters:

key - the key of the mapping to remove.

Returns:

the value of the removed mapping or null if no mapping for the specified key was found.

Throws:

ClassCastException - if the specified key cannot be compared with the keys in this map.

NullPointerException - if the specified key is null and the comparator cannot handle null keys.

size

public int size()

Returns the number of mappings in this map.

Specified by:

size in interface Map<K,V>

Overrides:

size in class AbstractMap<K,V>

Returns:

the number of mappings in this map.

values

public Collection<V> values()

Returns a collection of the values contained in this map. The collection is backed by this map so changes to one are reflected by the other. The collection supports remove, removeAll, retainAll and clear operations, and it does not support add or addAll operations.

This method returns a collection which is the subclass of AbstractCollection. The iterator method of this subclass returns a "wrapper object" over the iterator of map's entrySet(). The size method wraps the map's size method and the contains method wraps the map's containsValue method.

The collection is created when this method is called for the first time and returned in response to all subsequent calls. This method may return different collections when multiple concurrent calls occur, since no synchronization is performed.

Specified by:

values in interface Map<K,V>

Overrides:

values in class AbstractMap<K,V>

Returns:

a collection of the values contained in this map.

firstEntry

public Map.Entry<K,V> firstEntry()

Answers the entry with the smallest key, or null if the map is empty.

Specified by:

firstEntry in interface NavigableMap<K,V>

Returns:

the entry with the smallest key, or null if the map is empty

Since:

1.6

See Also:

NavigableMap.firstEntry()

lastEntry

public Map.Entry<K,V> lastEntry()

Answers the entry with the biggest key, or null if the map is empty.

Specified by:

lastEntry in interface NavigableMap<K,V>

Returns:

the entry with the biggest key, or null if the map is empty

Since:

1.6

See Also:

NavigableMap.lastEntry()

pollFirstEntry

public Map.Entry<K,V> pollFirstEntry()

Deletes and answers the entry with the smallest key, or null if the map is empty.

Specified by:

pollFirstEntry in interface NavigableMap<K,V>

Returns:

the entry with the smallest key, or null if the map is empty

Since:

1.6

See Also:

NavigableMap.pollFirstEntry()

pollLastEntry

public Map.Entry<K,V> pollLastEntry()

Deletes and answers the entry with the biggest key, or null if the map is empty.

Specified by:

pollLastEntry in interface NavigableMap<K,V>

Returns:

the entry with the biggest key, or null if the map is empty

Since:

1.6

See Also:

NavigableMap.pollLastEntry()

higherEntry

public Map.Entry<K,V> higherEntry(K key)

Answers an entry related with the smallest key greater than the specified key, or null if no such key.

Specified by:

higherEntry in interface NavigableMap<K,V>

Parameters:

key - the key

Returns:

the entry, or null if no such key

Since:

1.6

See Also:

NavigableMap.higherEntry(Object)

higherKey

public K higherKey(K key)

Answers the smallest key greater than the specified key, or null if no such key.

Specified by:

higherKey in interface NavigableMap<K,V>

Parameters:

key - the key

Returns:

the smallest key greater than key, or null if no such key

Since:

1.6

See Also:

NavigableMap.higherKey(Object)

lowerEntry

public Map.Entry<K,V> lowerEntry(K key)

Answers an entry related with the biggest key less than the specified key, or null if no such key.

Specified by:

lowerEntry in interface NavigableMap<K,V>

Parameters:

key - the key

Returns:

the entry, or null if no such key

Since:

1.6

See Also:

NavigableMap.lowerEntry(Object)

lowerKey

public K lowerKey(K key)

Answers the biggest key less than the specified key, or null if no such key.

Specified by:

lowerKey in interface NavigableMap<K,V>

Parameters:

key - the key

Returns:

the biggest key less than key, or null if no such key

Since:

1.6

See Also:

NavigableMap.lowerKey(Object)

ceilingEntry

public Map.Entry<K,V> ceilingEntry(K key)

Answers an entry related with the smallest key greater than or equal to the specified key, or null if no such key.

Specified by:

ceilingEntry in interface NavigableMap<K,V>

Parameters:

key - the key

Returns:

the entry, or null if no such key

Since:

1.6

See Also:

NavigableMap.ceilingEntry(java.lang.Object)

ceilingKey

public K ceilingKey(K key)

Answers the smallest key greater than or equal to the specified key, or null if no such key.

Specified by:

ceilingKey in interface NavigableMap<K,V>

Parameters:

key - the key

Returns:

the smallest key greater than or equal to key, or null if no such key

Since:

1.6

See Also:

NavigableMap.ceilingKey(java.lang.Object)

floorEntry

public Map.Entry<K,V> floorEntry(K key)

Answers an entry related with the biggest key less than or equal to the specified key, or null if no such key.

Specified by:

floorEntry in interface NavigableMap<K,V>

Parameters:

key - the key

Returns:

the entry, or null if no such key

Since:

1.6

See Also:

NavigableMap.floorEntry(Object)

floorKey

public K floorKey(K key)

Answers the biggest key less than or equal to the specified key, or null if no such key.

Specified by:

floorKey in interface NavigableMap<K,V>

Parameters:

key - the key

Returns:

the biggest key less than or equal to key, or null if no such key

Since:

1.6

See Also:

NavigableMap.floorKey(Object)

entrySet

public Set<Map.Entry<K,V>> entrySet()

Returns a set containing all of the mappings in this map. Each mapping is an instance of Map.Entry. As the set is backed by this map, changes in one will be reflected in the other. It does not support adding operations.

Specified by:

entrySet in interface Map<K,V>

Specified by:

entrySet in class AbstractMap<K,V>

Returns:

a set of the mappings.

navigableKeySet

public NavigableSet<K> navigableKeySet()

Answers a NavigableSet view of the keys in ascending order.

Specified by:

navigableKeySet in interface NavigableMap<K,V>

Returns:

the navigable set view

Since:

1.6

See Also:

NavigableMap.navigableKeySet()

descendingKeySet

public NavigableSet<K> descendingKeySet()

Answers a NavigableSet view of the keys in descending order.

Specified by:

descendingKeySet in interface NavigableMap<K,V>

Returns:

the navigable set view

Since:

1.6

See Also:

NavigableMap.descendingKeySet()

descendingMap

public NavigableMap<K,V> descendingMap()

Answers a reverse order view of the map.

Specified by:

descendingMap in interface NavigableMap<K,V>

Returns:

the reverse order view of the map

Since:

1.6

See Also:

NavigableMap.descendingMap()

subMap

public NavigableMap<K,V> subMap(K start,
                                boolean startInclusive,
                                K end,
                                boolean endInclusive)

Answers a view of part of the map whose keys is from startKey to endKey.

Specified by:

subMap in interface NavigableMap<K,V>

Parameters:

start - the start key

startInclusive - true if the start key is in the returned map

end - the end key

endInclusive - true if the end key is in the returned map

Returns:

the sub-map view

Since:

1.6

See Also:

NavigableMap.subMap(Object, boolean, Object, boolean)

headMap

public NavigableMap<K,V> headMap(K end,
                                 boolean inclusive)

Answers a view of the head of the map whose keys are smaller than (or equal to, depends on inclusive argument) endKey.

Specified by:

headMap in interface NavigableMap<K,V>

Parameters:

end - the end key

inclusive - true if the end key is in the returned map

Returns:

the head-map view

Since:

1.6

See Also:

NavigableMap.headMap(Object, boolean)

tailMap

public NavigableMap<K,V> tailMap(K start,
                                 boolean inclusive)

Answers a view of the tail of the map whose keys are bigger than (or equal to, depends on inclusive argument) startKey.

Specified by:

tailMap in interface NavigableMap<K,V>

Parameters:

start - the start key

inclusive - true if the start key is in the returned map

Returns:

the tail-map view

Since:

1.6

See Also:

NavigableMap.tailMap(Object, boolean)

subMap

public SortedMap<K,V> subMap(K startKey,
                             K endKey)

Returns a sorted map over a range of this sorted map with all keys greater than or equal to the specified startKey and less than the specified endKey. Changes to the returned sorted map are reflected in this sorted map and vice versa.

Note: The returned map will not allow an insertion of a key outside the specified range.

Specified by:

subMap in interface SortedMap<K,V>

Parameters:

startKey - the low boundary of the range (inclusive).

endKey - the high boundary of the range (exclusive),

Returns:

a sorted map with the key from the specified range.

Throws:

ClassCastException - if the start or end key cannot be compared with the keys in this map.

NullPointerException - if the start or end key is null and the comparator cannot handle null keys.

IllegalArgumentException - if the start key is greater than the end key, or if this map is itself a sorted map over a range of another sorted map and the specified range is outside of its range.

headMap

public SortedMap<K,V> headMap(K endKey)

Returns a sorted map over a range of this sorted map with all keys that are less than the specified endKey. Changes to the returned sorted map are reflected in this sorted map and vice versa.

Note: The returned map will not allow an insertion of a key outside the specified range.

Specified by:

headMap in interface SortedMap<K,V>

Parameters:

endKey - the high boundary of the range specified.

Returns:

a sorted map where the keys are less than endKey.

Throws:

ClassCastException - if the specified key cannot be compared with the keys in this map.

NullPointerException - if the specified key is null and the comparator cannot handle null keys.

IllegalArgumentException - if this map is itself a sorted map over a range of another map and the specified key is outside of its range.

tailMap

public SortedMap<K,V> tailMap(K startKey)

Returns a sorted map over a range of this sorted map with all keys that are greater than or equal to the specified startKey. Changes to the returned sorted map are reflected in this sorted map and vice versa.

Note: The returned map will not allow an insertion of a key outside the specified range.

Specified by:

tailMap in interface SortedMap<K,V>

Parameters:

startKey - the low boundary of the range specified.

Returns:

a sorted map where the keys are greater or equal to startKey.

Throws:

ClassCastException - if the specified key cannot be compared with the keys in this map.

NullPointerException - if the specified key is null and the comparator cannot handle null keys.

IllegalArgumentException - if this map itself a sorted map over a range of another map and the specified key is outside of its range.