java.util

Class TreeSet<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractSet<E>

java.util.TreeSet<E>

All Implemented Interfaces:

Iterable<E>, Collection<E>, NavigableSet<E>, Set<E>, SortedSet<E>

public class TreeSet<E>
extends AbstractSet<E>
implements NavigableSet<E>

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

Since:

1.2

Constructor Summary

Constructors

Constructor and Description
TreeSet() Constructs a new empty instance of TreeSet which uses natural ordering.
TreeSet(Collection<? extends E> collection) Constructs a new instance of TreeSet which uses natural ordering and containing the unique elements in the specified collection.
TreeSet(Comparator<? super E> comparator) Constructs a new empty instance of TreeSet which uses the specified comparator.
TreeSet(SortedSet<E> set) Constructs a new instance of TreeSet containing the elements of the specified SortedSet and using the same Comparator.

Method Summary

Modifier and Type	Method and Description
boolean	add(E object) Adds the specified object to this TreeSet.
boolean	addAll(Collection<? extends E> collection) Adds the objects in the specified collection to this TreeSet.
E	ceiling(E e) Answers the smallest element bigger than or equal to the specified one, or null if no such element.
void	clear() Removes all elements from this TreeSet, leaving it empty.
Comparator<? super E>	comparator() Returns the comparator used to compare elements in this TreeSet.
boolean	contains(Object object) Searches this TreeSet for the specified object.
Iterator<E>	descendingIterator() Answers a descending iterator of this set.
NavigableSet<E>	descendingSet() Answers a reverse order view of this set.
E	first() Answers the first element in this TreeSet.
E	floor(E e) Answers the biggest element less than or equal to the specified one, or null if no such element.
SortedSet<E>	headSet(E end) Answers a SortedSet of the specified portion of this TreeSet which contains elements less than the end element.
NavigableSet<E>	headSet(E end, boolean endInclusive) Answers a NavigableSet of the specified portion of this set which contains elements less than (or equal to, depends on endInclusive) the end element.
E	higher(E e) Answers the smallest element bigger than the specified one, or null if no such element.
boolean	isEmpty() Returns true if this TreeSet has no element, otherwise false.
Iterator<E>	iterator() Returns an Iterator on the elements of this TreeSet.
E	last() Answers the last element in this TreeSet.
E	lower(E e) Answers the biggest element less than the specified one, or null if no such element.
E	pollFirst() Deletes and answers the smallest element, or null if the set is empty.
E	pollLast() Deletes and answers the biggest element, or null if the set is empty.
boolean	remove(Object object) Removes an occurrence of the specified object from this TreeSet.
int	size() Returns the number of elements in this TreeSet.
NavigableSet<E>	subSet(E start, boolean startInclusive, E end, boolean endInclusive) Answers a NavigableSet of the specified portion of this set which contains elements greater (or equal to, depends on startInclusive) the start element but less than (or equal to, depends on endInclusive) the end element.
SortedSet<E>	subSet(E start, E 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<E>	tailSet(E start) Answers a SortedSet of the specified portion of this TreeSet which contains elements greater or equal to the start element.
NavigableSet<E>	tailSet(E start, boolean startInclusive) Answers a NavigableSet of the specified portion of this set which contains elements greater (or equal to, depends on startInclusive) 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

clone, 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()

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

TreeSet

public TreeSet(Collection<? extends E> 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<? super E> comparator)

Constructs a new empty instance of TreeSet which uses the specified comparator.

Parameters:

comparator - the comparator to use.

TreeSet

public TreeSet(SortedSet<E> set)

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

Parameters:

set - the SortedSet of elements to add.

Method Detail

add

public boolean add(E object)

Adds the specified object to this TreeSet.

Specified by:

add in interface Collection<E>

Specified by:

add in interface Set<E>

Overrides:

add in class AbstractCollection<E>

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<? extends E> collection)

Adds the objects in the specified collection to this TreeSet.

Specified by:

addAll in interface Collection<E>

Specified by:

addAll in interface Set<E>

Overrides:

addAll in class AbstractCollection<E>

Parameters:

collection - the collection of objects to add.

Returns:

true if this TreeSet was 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 Collection<E>

Specified by:

clear in interface Set<E>

Overrides:

clear in class AbstractCollection<E>

See Also:

isEmpty(), size()

comparator

public Comparator<? super E> comparator()

Returns the comparator used to compare elements in this TreeSet.

Specified by:

comparator in interface SortedSet<E>

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 Collection<E>

Specified by:

contains in interface Set<E>

Overrides:

contains in class AbstractCollection<E>

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.

isEmpty

public boolean isEmpty()

Returns true if this TreeSet has no element, otherwise false.

Specified by:

isEmpty in interface Collection<E>

Specified by:

isEmpty in interface Set<E>

Overrides:

isEmpty in class AbstractCollection<E>

Returns:

true if this TreeSet has no element.

See Also:

size()

iterator

public Iterator<E> iterator()

Returns an Iterator on the elements of this TreeSet.

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in interface Collection<E>

Specified by:

iterator in interface Set<E>

Specified by:

iterator in class AbstractCollection<E>

Returns:

an Iterator on the elements of this TreeSet.

See Also:

Iterator

descendingIterator

public Iterator<E> descendingIterator()

Answers a descending iterator of this set.

Specified by:

descendingIterator in interface NavigableSet<E>

Returns:

the descending iterator

Since:

1.6

See Also:

NavigableSet.descendingIterator()

remove

public boolean remove(Object object)

Removes an occurrence of the specified object from this TreeSet.

Specified by:

remove in interface Collection<E>

Specified by:

remove in interface Set<E>

Overrides:

remove in class AbstractCollection<E>

Parameters:

object - the object to remove.

Returns:

true if this TreeSet was 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()

Returns the number of elements in this TreeSet.

Specified by:

size in interface Collection<E>

Specified by:

size in interface Set<E>

Specified by:

size in class AbstractCollection<E>

Returns:

the number of elements in this TreeSet.

first

public E first()

Answers the first element in this TreeSet.

Specified by:

first in interface SortedSet<E>

Returns:

the first element

Throws:

NoSuchElementException - when this TreeSet is empty

last

public E last()

Answers the last element in this TreeSet.

Specified by:

last in interface SortedSet<E>

Returns:

the last element

Throws:

NoSuchElementException - when this TreeSet is empty

pollFirst

public E pollFirst()

Deletes and answers the smallest element, or null if the set is empty.

Specified by:

pollFirst in interface NavigableSet<E>

Returns:

the smallest element, or null if the set is empty

Since:

1.6

See Also:

NavigableSet.pollFirst()

pollLast

public E pollLast()

Deletes and answers the biggest element, or null if the set is empty.

Specified by:

pollLast in interface NavigableSet<E>

Returns:

the biggest element, or null if the set is empty

Since:

1.6

See Also:

NavigableSet.pollLast()

higher

public E higher(E e)

Answers the smallest element bigger than the specified one, or null if no such element.

Specified by:

higher in interface NavigableSet<E>

Parameters:

e - the specified element

Returns:

the smallest element bigger than the specified one, or null if no such element

Since:

1.6

See Also:

NavigableSet.higher(java.lang.Object)

lower

public E lower(E e)

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

Specified by:

lower in interface NavigableSet<E>

Parameters:

e - the specified element

Returns:

the biggest element less than the specified one, or null if no such element

Since:

1.6

See Also:

NavigableSet.lower(java.lang.Object)

ceiling

public E ceiling(E e)

Answers the smallest element bigger than or equal to the specified one, or null if no such element.

Specified by:

ceiling in interface NavigableSet<E>

Parameters:

e - the specified element

Returns:

the smallest element bigger than or equal to the specified one, or null if no such element

Since:

1.6

See Also:

NavigableSet.ceiling(java.lang.Object)

floor

public E floor(E e)

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

Specified by:

floor in interface NavigableSet<E>

Parameters:

e - the specified element

Returns:

the biggest element less than or equal to the specified one, or null if no such element

Since:

1.6

See Also:

NavigableSet.floor(java.lang.Object)

descendingSet

public NavigableSet<E> descendingSet()

Answers a reverse order view of this set.

Specified by:

descendingSet in interface NavigableSet<E>

Returns:

the reverse order view

Since:

1.6

See Also:

NavigableSet.descendingSet()

subSet

public NavigableSet<E> subSet(E start,
                              boolean startInclusive,
                              E end,
                              boolean endInclusive)

Answers a NavigableSet of the specified portion of this set which contains elements greater (or equal to, depends on startInclusive) the start element but less than (or equal to, depends on endInclusive) the end element. The returned NavigableSet is backed by this set so changes to one are reflected by the other.

Specified by:

subSet in interface NavigableSet<E>

Parameters:

start - the start element

startInclusive - true if the start element is in the returned set

end - the end element

endInclusive - true if the end element is in the returned set

Returns:

the subset

Since:

1.6

See Also:

NavigableSet.subSet(Object, boolean, Object, boolean)

headSet

public NavigableSet<E> headSet(E end,
                               boolean endInclusive)

Answers a NavigableSet of the specified portion of this set which contains elements less than (or equal to, depends on endInclusive) the end element. The returned NavigableSet is backed by this set so changes to one are reflected by the other.

Specified by:

headSet in interface NavigableSet<E>

Parameters:

end - the end element

endInclusive - true if the end element is in the returned set

Returns:

the subset

Since:

1.6

See Also:

NavigableSet.headSet(Object, boolean)

tailSet

public NavigableSet<E> tailSet(E start,
                               boolean startInclusive)

Answers a NavigableSet of the specified portion of this set which contains elements greater (or equal to, depends on startInclusive) the start element. The returned NavigableSet is backed by this set so changes to one are reflected by the other.

Specified by:

tailSet in interface NavigableSet<E>

Parameters:

start - the start element

startInclusive - true if the start element is in the returned set

Returns:

the subset

Since:

1.6

See Also:

NavigableSet.tailSet(Object, boolean)

subSet

public SortedSet<E> subSet(E start,
                           E 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<E>

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

headSet

public SortedSet<E> headSet(E 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<E>

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

tailSet

public SortedSet<E> tailSet(E 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<E>

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