Class java.util.TreeMap


Overview \| Package \| Class \| Tree \| Index \| Help
PREV CLASS \| NEXT CLASS	FRAMES \| NO FRAMES
SUMMARY: INNER \| FIELD \| CONSTR \| METHOD	DETAIL: FIELD \| CONSTR \| METHOD

Class java.util.TreeMap

java.lang.Object
  |
  +--java.util.AbstractMap
        |
        +--java.util.TreeMap

public class TreeMap
extends AbstractMap
implements SortedMap, java.lang.Cloneable, java.io.Serializable

Red-Black tree based implementation of the Map interface. This class guarantees that the Map will be in ascending key order, sorted according to the natural order for the key Class (see Comparable), or by the Comparator provided at TreeMap creation time, depending on which constructor is used. Note that this ordering must be total in order for the Tree to function properly. (A total ordering is an ordering for which a.compareTo(b)==0 implies that a.equals(b); see OrderedMap for further details.)

This implementation provides guaranteed log(n) time cost for the containsKey, get, put and remove operations. Algorithms are adaptations of those in Corman, Leiserson, and Rivest's Introduction to Algorithms.

Note that this implementation is not synchronized. If multiple threads access a TreeMap concurrently, and at least one of the threads modifies the TreeMap 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 a key that is already contained in the Table is not a structural modification.) This is typically accomplished by synchronizing on some object that naturally encapsulates the TreeMap. If no such object exists, the TreeMap should be "wrapped" using the Collections.synchronizedSet method. This is best done at creation time, to prevent accidental unsynchronized access to the TreeMap:

	Map m = Collections.synchronizedMap(new TreeMap(...));

The Iterators returned by the iterator methods of the Collections returned by all of TreeMap's "collection view methods" are fail-fast: if the TreeMap is structurally modified at any time after the Iterator is created, in any way except through the Iterator's own remove or add methods, 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.

Since:: JDK1.2
Version:: 1.27, 05/06/98
See Also:: Map, HashMap, Hashtable, java.lang.Comparable, Comparator, Collection, Collections#synchronizedMap(), Serialized Form

Inner Class Summary
static	TreeMap.Entry Node in the Tree.

Constructor Summary
TreeMap() Constructs a new, empty TreeMap, sorted according to the keys' natural order.
TreeMap(Comparator c) Constructs a new, empty TreeMap, sorted according to the given comparator.
TreeMap(Map m) Constructs a new TreeMap containing the same mappings as the given Map, sorted according to the keys' natural order.
TreeMap(SortedMap m) Constructs a new TreeMap containing the same mappings as the given SortedMap, sorted according to the same ordering.

Method Summary
void	clear() Removes all mappings from this TreeMap.
java.lang.Object	clone() Returns a shallow copy of this TreeSet.
Comparator	comparator() Returns the comparator used to order this TreeMap, or null if this TreeMap uses its keys' natural order.
boolean	containsKey(java.lang.Object key) Returns true if this TreeMap contains a mapping for the specified key.
Set	entrySet() Returns a Set view of the mappings contained in this Map.
java.lang.Object	firstKey() Returns the first (lowest) key currently in this SortedMap.
java.lang.Object	get(java.lang.Object key) Returns the value to which this TreeMap maps the specified key.
SortedMap	headMap(java.lang.Object toKey) Returns a view of the portion of this TreeMap whose keys are strictly less than toKey.
Set	keySet() Returns a Set view of the keys contained in this TreeMap.
java.lang.Object	lastKey() Returns the last (highest) key currently in this SortedMap.
java.lang.Object	put(java.lang.Object key, java.lang.Object value) Associates the specified value with the specified key in this TreeMap.
java.lang.Object	remove(java.lang.Object key) Removes the mapping for this key from this TreeMap if present.
int	size() Returns the number of key-value mappings in this TreeMap.
SortedMap	subMap(java.lang.Object fromKey, java.lang.Object toKey) Returns a view of the portion of this TreeMap whose keys range from fromKey, inclusive, to toKey, exclusive.
SortedMap	tailMap(java.lang.Object fromKey) Returns a view of the portion of this TreeMap whose keys are strictly less than toKey.
Collection	values() Returns a Collection view of the values contained in this TreeMap.

Methods inherited from class java.util.AbstractMap
clear, containsKey, containsValue, entrySet, equals, get, hashCode, isEmpty, keySet, put, putAll, remove, size, toString, values

Methods inherited from class java.lang.Object
, clone, equals, finalize, getClass, hashCode, notifyAll, notify, toString, wait, wait, wait

Constructor Detail

TreeMap

public TreeMap()

Constructs a new, empty TreeMap, sorted according to the keys' natural order. All keys inserted into the TreeMap must implement the Comparable interface. Furthermore, all such keys must be mutually comparable: k1.compareTo(k2) must not throw a typeMismatchException for any elements k1 and k2 in the TreeMap. If the user attempts to put a key into the TreeMap that violates this constraint (for example, the user attempts to put a String key into a TreeMap whose keys are Integers), the put(Object key, Object value) call will throw a ClassCastException.

See Also:: java.lang.Comparable

TreeMap

public TreeMap(Comparator c)

Constructs a new, empty TreeMap, sorted according to the given comparator. All keys inserted into the TreeMap must be mutually comparable by the given comparator: comparator.compare(k1, k2) must not throw a typeMismatchException for any keys k1 and k2 in the TreeMap. If the user attempts to put a key into the TreeMap that violates this constraint, the put(Object key, Object value) call will throw a ClassCastException.

TreeMap

public TreeMap(Map m)

Constructs a new TreeMap containing the same mappings as the given Map, sorted according to the keys' natural order. All keys inserted into the TreeMap must implement the Comparable interface. Furthermore, all such keys must be mutually comparable: k1.compareTo(k2) must not throw a typeMismatchException for any elements k1 and k2 in the TreeMap.

Throws:: ClassCastException - the keys in t are not Comparable, or are not mutually comparable.

TreeMap

public TreeMap(SortedMap m)

Constructs a new TreeMap containing the same mappings as the given SortedMap, sorted according to the same ordering.

Method Detail

size

public int size()

Returns the number of key-value mappings in this TreeMap.

Overrides:: size in class AbstractMap

containsKey

public boolean containsKey(java.lang.Object key)

Returns true if this TreeMap contains a mapping for the specified key.

Parameters:: key - key whose presence in this Map is to be tested.
Throws:: ClassCastException - key cannot be compared with the keys currently in the TreeMap.; NullPointerException - key is null and this TreeMap uses natural ordering, or its comparator does not tolerate null keys.
Overrides:: containsKey in class AbstractMap

get

public java.lang.Object get(java.lang.Object key)

Returns the value to which this TreeMap maps the specified key. Returns null if the TreeMap contains no mapping for this key. A return value of null does not necessarily indicate that the TreeMap contains no mapping for the key; it's also possible that the TreeMap explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

Parameters:: key - key whose associated value is to be returned.
Throws:: ClassCastException - key cannot be compared with the keys currently in the TreeMap.; NullPointerException - key is null and this TreeMap uses natural ordering, or its comparator does not tolerate null keys.
Overrides:: get in class AbstractMap
See Also:: containsKey(Object)

comparator

public Comparator comparator()

Returns the comparator used to order this TreeMap, or null if this TreeMap uses its keys' natural order.

Specified by:: comparator in interface SortedMap
Returns:: the Comparator associated with this SortedMap, or null if it uses its keys' natural sort method.

firstKey

public java.lang.Object firstKey()

Returns the first (lowest) key currently in this SortedMap.

Specified by:: firstKey in interface SortedMap
Returns:: the first (lowest) key currently in this SortedMap.
Throws:: NoSuchElementException - Map is empty.

lastKey

public java.lang.Object lastKey()

Returns the last (highest) key currently in this SortedMap.

Specified by:: lastKey in interface SortedMap
Returns:: the last (highest) key currently in this SortedMap.
Throws:: NoSuchElementException - Map is empty.

put

public java.lang.Object put(java.lang.Object key,
                  java.lang.Object value)

Associates the specified value with the specified key in this TreeMap. If the TreeMap previously contained a mapping for this key, the old value is replaced.

Parameters:: key - key with which the specified value is to be associated.; value - value to be associated with the specified key.
Returns:: previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the TreeMap previously associated null with the specified key.
Throws:: ClassCastException - key cannot be compared with the keys currently in the TreeMap.; NullPointerException - key is null and this TreeMap uses natural order, or its comparator does not tolerate null keys.
Overrides:: put in class AbstractMap

remove

public java.lang.Object remove(java.lang.Object key)

Removes the mapping for this key from this TreeMap if present.

Returns:: previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the TreeMap previously associated null with the specified key.
Throws:: ClassCastException - key cannot be compared with the keys currently in the TreeMap.; NullPointerException - key is null and this TreeMap uses natural order, or its comparator does not tolerate null keys.
Overrides:: remove in class AbstractMap

clear

public void clear()

Removes all mappings from this TreeMap.

Overrides:: clear in class AbstractMap

clone

public java.lang.Object clone()

Returns a shallow copy of this TreeSet. (The elements themselves are not cloned.)

Overrides:: clone in class java.lang.Object

keySet

public Set keySet()

Returns a Set view of the keys contained in this TreeMap. The Set's Iterator will return the keys in ascending order. The Set is backed by the TreeMap, so changes to the TreeMap are reflected in the Set, and vice-versa. The Set supports element removal, which removes the corresponding mapping from the TreeMap, via the Iterator.remove, Set.remove, removeAll retainAll, and clear operations. It does not support the add or addAll operations.

Overrides:: keySet in class AbstractMap

values

public Collection values()

Returns a Collection view of the values contained in this TreeMap. The Collection's iterator will return the values in the order that their corresponding keys appear in the tree. The Collection is backed by the TreeMap, so changes to the TreeMap are reflected in the Collection, and vice-versa. The Collection supports element removal, which removes the corresponding mapping from the TreeMap, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Overrides:: values in class AbstractMap

entrySet

public Set entrySet()

Returns a Set view of the mappings contained in this Map. The Set's Iterator will return the mappings in ascending Key order. Each element in the returned set is a Map.Entry. The Set is backed by the TreeMap, so changes to the TreeMap are reflected in the Set, and vice-versa. The Set supports element removal, which removes the corresponding mapping from the TreeMap, via the Iterator.remove, Set.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Overrides:: entrySet in class AbstractMap
See Also:: Map.Entry

subMap

public SortedMap subMap(java.lang.Object fromKey,
                        java.lang.Object toKey)

Returns a view of the portion of this TreeMap whose keys range from fromKey, inclusive, to toKey, exclusive. The returned Map is backed by this TreeMap, so changes in the returned Map are reflected in this TreeMap, and vice-versa. The returned Map supports all optional Map operations.

The Map returned by this method will throw an IllegalArgumentException if the user attempts to insert a key less than fromKey or greater than or equal to toKey.

Specified by:: subMap in interface SortedMap
Parameters:: fromKey - low endpoint (inclusive) of the subMap.; toKey - high endpoint (exclusive) of the subMap.
Throws:: ClassCastException - fromKey or toKey cannot be compared with the keys currently in the TreeMap.; NullPointerException - fromKey or toKey is null and this TreeMap uses natural order, or its comparator does not tolerate null keys.; java.lang.IllegalArgumentException - fromKey is greater than toKey.

headMap

public SortedMap headMap(java.lang.Object toKey)

Returns a view of the portion of this TreeMap whose keys are strictly less than toKey. The returned Map is backed by this TreeMap, so changes in the returned Map are reflected in this TreeMap, and vice-versa. The returned Map supports all optional Map operations.

The Map returned by this method will throw an IllegalArgumentException if the user attempts to insert a key greater than or equal to toKey.

Specified by:: headMap in interface SortedMap
Parameters:: toKey - high endpoint (exclusive) of the headMap.
Throws:: ClassCastException - toKey cannot be compared with the keys currently in the TreeMap.; NullPointerException - toKey is null and this TreeMap uses natural order, or its comparator does not tolerate null keys.

tailMap

public SortedMap tailMap(java.lang.Object fromKey)

The Map returned by this method will throw an IllegalArgumentException if the user attempts to insert a key greater than or equal to toKey.

Specified by:: tailMap in interface SortedMap
Parameters:: toKey - high endpoint (exclusive) of the headMap.
Throws:: ClassCastException - toKey cannot be compared with the keys currently in the TreeMap.; NullPointerException - toKey is null and this TreeMap uses natural ordering, or its comparator does not tolerate null keys.


Overview \| Package \| Class \| Tree \| Index \| Help
PREV CLASS \| NEXT CLASS	FRAMES \| NO FRAMES
SUMMARY: INNER \| FIELD \| CONSTR \| METHOD	DETAIL: FIELD \| CONSTR \| METHOD


Overview \| Package \| Class \| Tree \| Index \| Help
PREV CLASS \| NEXT CLASS	FRAMES \| NO FRAMES
SUMMARY: INNER \| FIELD \| CONSTR \| METHOD	DETAIL: FIELD \| CONSTR \| METHOD


Overview \| Package \| Class \| Tree \| Index \| Help
PREV CLASS \| NEXT CLASS	FRAMES \| NO FRAMES
SUMMARY: INNER \| FIELD \| CONSTR \| METHOD	DETAIL: FIELD \| CONSTR \| METHOD