java.util
Class TreeSet

java.lang.Object
  java.util.AbstractCollection
      java.util.AbstractSet
          java.util.TreeSet

All Implemented Interfaces:

Cloneable, Collection, Serializable, Set, SortedSet

public class TreeSet

extends AbstractSet

implements SortedSet, Cloneable, Serializable

TreeSet is an implementation of SortedSet. All optional operations are supported, adding and removing. The elements can be any objects which are comparable to each other either using their natural order or a specified Comparator.

See Also:

Serialized Form

Constructor Summary

TreeSet()
Contructs a new empty instance of TreeSet which uses natural ordering.

TreeSet(Collection collection)
Constructs a new instance of TreeSet which uses natural ordering and containing the unique elements in the specified collection.

TreeSet(Comparator comparator)
Contructs a new empty instance of TreeSet which uses the specified Comparator.

TreeSet(SortedSet set)
Constructs a new instance of TreeSet containing the elements in the specified SortedSet and using the same Comparator.

Method Summary

boolean	add(Object object) Adds the specified object to this TreeSet.
boolean	addAll(Collection collection) Adds the objects in the specified Collection to this TreeSet.
void	clear() Removes all elements from this TreeSet, leaving it empty.
Object	clone() Answers a new TreeSet with the same elements, size and comparator as this TreeSet.
Comparator	comparator() Answers the Comparator used to compare elements in this TreeSet.
boolean	contains(Object object) Searches this TreeSet for the specified object.
Object	first() Answers the first element in this TreeSet.
SortedSet	headSet(Object end) Answers a SortedSet of the specified portion of this TreeSet which contains elements less than the end element.
boolean	isEmpty() Answers if this TreeSet has no elements, a size of zero.
Iterator	iterator() Answers an Iterator on the elements of this TreeSet.
Object	last() Answers the last element in this TreeSet.
boolean	remove(Object object) Removes an occurrence of the specified object from this TreeSet.
int	size() Answers the number of elements in this TreeSet.
SortedSet	subSet(Object start, Object end) Answers a SortedSet of the specified portion of this TreeSet which contains elements greater or equal to the start element but less than the end element.
SortedSet	tailSet(Object start) Answers a SortedSet of the specified portion of this TreeSet which contains elements greater or equal to the start element.

Methods inherited from class java.util.AbstractSet

equals, hashCode, removeAll

Methods inherited from class java.util.AbstractCollection

containsAll, retainAll, toArray, toArray, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Set

containsAll, equals, hashCode, removeAll, retainAll, toArray, toArray

Constructor Detail

TreeSet

public TreeSet()

Contructs a new empty instance of TreeSet which uses natural ordering.

TreeSet

public TreeSet(Collection collection)

Constructs a new instance of TreeSet which uses natural ordering and containing the unique elements in the specified collection.

Parameters:

collection - the collection of elements to add

Throws:

ClassCastException - when an element in the Collection does not implement the Comparable interface, or the elements in the Collection cannot be compared

TreeSet

public TreeSet(Comparator comparator)

Contructs a new empty instance of TreeSet which uses the specified Comparator.

Parameters:

comparator - the Comparator

TreeSet

public TreeSet(SortedSet set)

Constructs a new instance of TreeSet containing the elements in the specified SortedSet and using the same Comparator.

Parameters:

set - the SortedSet of elements to add

Method Detail

add

public boolean add(Object object)

Adds the specified object to this TreeSet.

Specified by:

add in interface Set

Overrides:

add in class AbstractCollection

Parameters:

object - the object to add

Returns:

true when this TreeSet did not already contain the object, false otherwise

Throws:

ClassCastException - when the object cannot be compared with the elements in this TreeSet

NullPointerException - when the object is null and the comparator cannot handle null

addAll

public boolean addAll(Collection collection)

Adds the objects in the specified Collection to this TreeSet.

Specified by:

addAll in interface Set

Overrides:

addAll in class AbstractCollection

Parameters:

collection - the Collection of objects

Returns:

true if this TreeSet is modified, false otherwise

Throws:

ClassCastException - when an object in the Collection cannot be compared with the elements in this TreeSet

NullPointerException - when an object in the Collection is null and the comparator cannot handle null

clear

public void clear()

Removes all elements from this TreeSet, leaving it empty.

Specified by:

clear in interface Set

Overrides:

clear in class AbstractCollection

See Also:

isEmpty(), size()

clone

public Object clone()

Answers a new TreeSet with the same elements, size and comparator as this TreeSet.

Overrides:

clone in class Object

Returns:

a shallow copy of this TreeSet

See Also:

Cloneable

comparator

public Comparator comparator()

Answers the Comparator used to compare elements in this TreeSet.

Specified by:

comparator in interface SortedSet

Returns:

a Comparator or null if the natural ordering is used

contains

public boolean contains(Object object)

Searches this TreeSet for the specified object.

Specified by:

contains in interface Set

Overrides:

contains in class AbstractCollection

Parameters:

object - the object to search for

Returns:

true if object is an element of this TreeSet, false otherwise

Throws:

ClassCastException - when the object cannot be compared with the elements in this TreeSet

NullPointerException - when the object is null and the comparator cannot handle null

first

public Object first()

Answers the first element in this TreeSet.

Specified by:

first in interface SortedSet

Returns:

the first element

Throws:

NoSuchElementException - when this TreeSet is empty

headSet

public SortedSet headSet(Object end)

Answers a SortedSet of the specified portion of this TreeSet which contains elements less than the end element. The returned SortedSet is backed by this TreeSet so changes to one are reflected by the other.

Specified by:

headSet in interface SortedSet

Parameters:

end - the end element

Returns:

a subset where the elements are less than end

Throws:

ClassCastException - when the end object cannot be compared with the elements in this TreeSet

NullPointerException - when the end object is null and the comparator cannot handle null

isEmpty

public boolean isEmpty()

Answers if this TreeSet has no elements, a size of zero.

Specified by:

isEmpty in interface Set

Overrides:

isEmpty in class AbstractCollection

Returns:

true if this TreeSet has no elements, false otherwise

See Also:

size()

iterator

public Iterator iterator()

Answers an Iterator on the elements of this TreeSet.

Specified by:

iterator in interface Set

Specified by:

iterator in class AbstractCollection

Returns:

an Iterator on the elements of this TreeSet

See Also:

Iterator

last

public Object last()

Answers the last element in this TreeSet.

Specified by:

last in interface SortedSet

Returns:

the last element

Throws:

NoSuchElementException - when this TreeSet is empty

remove

public boolean remove(Object object)

Removes an occurrence of the specified object from this TreeSet.

Specified by:

remove in interface Set

Overrides:

remove in class AbstractCollection

Parameters:

object - the object to remove

Returns:

true if this TreeSet is modified, false otherwise

Throws:

ClassCastException - when the object cannot be compared with the elements in this TreeSet

NullPointerException - when the object is null and the comparator cannot handle null

size

public int size()

Answers the number of elements in this TreeSet.

Specified by:

size in interface Set

Specified by:

size in class AbstractCollection

Returns:

the number of elements in this TreeSet

subSet

public SortedSet subSet(Object start,
                        Object end)

Answers a SortedSet of the specified portion of this TreeSet which contains elements greater or equal to the start element but less than the end element. The returned SortedSet is backed by this TreeSet so changes to one are reflected by the other.

Specified by:

subSet in interface SortedSet

Parameters:

start - the start element

end - the end element

Returns:

a subset where the elements are greater or equal to start and less than end

Throws:

ClassCastException - when the start or end object cannot be compared with the elements in this TreeSet

NullPointerException - when the start or end object is null and the comparator cannot handle null

tailSet

public SortedSet tailSet(Object start)

Answers a SortedSet of the specified portion of this TreeSet which contains elements greater or equal to the start element. The returned SortedSet is backed by this TreeSet so changes to one are reflected by the other.

Specified by:

tailSet in interface SortedSet

Parameters:

start - the start element

Returns:

a subset where the elements are greater or equal to start

Throws:

ClassCastException - when the start object cannot be compared with the elements in this TreeSet

NullPointerException - when the start object is null and the comparator cannot handle null