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Java™ Platform Standard Ed. 6 |
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java.lang.Object java.util.AbstractCollection<E> java.util.AbstractSet<E> java.util.TreeSet<E>
E
- the type of elements maintained by this setpublic class TreeSet<E>
A NavigableSet
implementation based on a TreeMap
.
The elements are ordered using their natural
ordering, or by a Comparator
provided at set creation
time, depending on which constructor is used.
This implementation provides guaranteed log(n) time cost for the basic
operations (add
, remove
and contains
).
Note that the ordering maintained by a set (whether or not an explicit
comparator is provided) must be consistent with equals if it is to
correctly implement the Set
interface. (See Comparable
or Comparator
for a precise definition of consistent with
equals.) This is so because the Set
interface is defined in
terms of the equals
operation, but a TreeSet
instance
performs all element comparisons using its compareTo
(or
compare
) method, so two elements that are deemed equal by this method
are, from the standpoint of the set, equal. The behavior of a set
is well-defined even if its ordering is inconsistent with equals; it
just fails to obey the general contract of the Set
interface.
Note that this implementation is not synchronized.
If multiple threads access a tree set concurrently, and at least one
of the threads modifies the set, it must be synchronized
externally. This is typically accomplished by synchronizing on some
object that naturally encapsulates the set.
If no such object exists, the set should be "wrapped" using the
Collections.synchronizedSortedSet
method. This is best done at creation time, to prevent accidental
unsynchronized access to the set:
SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));
The iterators returned by this class's iterator
method are
fail-fast: if the set is 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.
This class is a member of the Java Collections Framework.
Collection
,
Set
,
HashSet
,
Comparable
,
Comparator
,
TreeMap
,
Serialized FormConstructor Summary | |
---|---|
TreeSet()
Constructs a new, empty tree set, sorted according to the natural ordering of its elements. |
|
TreeSet(Collection<? extends E> c)
Constructs a new tree set containing the elements in the specified collection, sorted according to the natural ordering of its elements. |
|
TreeSet(Comparator<? super E> comparator)
Constructs a new, empty tree set, sorted according to the specified comparator. |
|
TreeSet(SortedSet<E> s)
Constructs a new tree set containing the same elements and using the same ordering as the specified sorted set. |
Method Summary | |
---|---|
boolean |
add(E e)
Adds the specified element to this set if it is not already present. |
boolean |
addAll(Collection<? extends E> c)
Adds all of the elements in the specified collection to this set. |
E |
ceiling(E e)
Returns the least element in this set greater than or equal to the given element, or null if there is no such element. |
void |
clear()
Removes all of the elements from this set. |
Object |
clone()
Returns a shallow copy of this TreeSet instance. |
Comparator<? super E> |
comparator()
Returns the comparator used to order the elements in this set, or null if this set uses the natural ordering of its elements. |
boolean |
contains(Object o)
Returns true if this set contains the specified element. |
Iterator<E> |
descendingIterator()
Returns an iterator over the elements in this set in descending order. |
NavigableSet<E> |
descendingSet()
Returns a reverse order view of the elements contained in this set. |
E |
first()
Returns the first (lowest) element currently in this set. |
E |
floor(E e)
Returns the greatest element in this set less than or equal to the given element, or null if there is no such element. |
SortedSet<E> |
headSet(E toElement)
Returns a view of the portion of this set whose elements are strictly less than toElement. |
NavigableSet<E> |
headSet(E toElement,
boolean inclusive)
Returns a view of the portion of this set whose elements are less than (or equal to, if inclusive is true) toElement . |
E |
higher(E e)
Returns the least element in this set strictly greater than the given element, or null if there is no such element. |
boolean |
isEmpty()
Returns true if this set contains no elements. |
Iterator<E> |
iterator()
Returns an iterator over the elements in this set in ascending order. |
E |
last()
Returns the last (highest) element currently in this set. |
E |
lower(E e)
Returns the greatest element in this set strictly less than the given element, or null if there is no such element. |
E |
pollFirst()
Retrieves and removes the first (lowest) element, or returns null if this set is empty. |
E |
pollLast()
Retrieves and removes the last (highest) element, or returns null if this set is empty. |
boolean |
remove(Object o)
Removes the specified element from this set if it is present. |
int |
size()
Returns the number of elements in this set (its cardinality). |
NavigableSet<E> |
subSet(E fromElement,
boolean fromInclusive,
E toElement,
boolean toInclusive)
Returns a view of the portion of this set whose elements range from fromElement to toElement . |
SortedSet<E> |
subSet(E fromElement,
E toElement)
Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive. |
SortedSet<E> |
tailSet(E fromElement)
Returns a view of the portion of this set whose elements are greater than or equal to fromElement. |
NavigableSet<E> |
tailSet(E fromElement,
boolean inclusive)
Returns a view of the portion of this set whose elements are greater than (or equal to, if inclusive is true) fromElement . |
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 |
---|
public TreeSet()
Comparable
interface.
Furthermore, all such elements must be mutually
comparable: e1.compareTo(e2)
must not throw a
ClassCastException
for any elements e1
and
e2
in the set. If the user attempts to add an element
to the set that violates this constraint (for example, the user
attempts to add a string element to a set whose elements are
integers), the add
call will throw a
ClassCastException
.
public TreeSet(Comparator<? super E> comparator)
comparator.compare(e1,
e2)
must not throw a ClassCastException
for any elements
e1
and e2
in the set. If the user attempts to add
an element to the set that violates this constraint, the
add
call will throw a ClassCastException
.
comparator
- the comparator that will be used to order this set.
If null
, the natural
ordering of the elements will be used.public TreeSet(Collection<? extends E> c)
Comparable
interface. Furthermore, all such elements must be
mutually comparable: e1.compareTo(e2)
must not throw a
ClassCastException
for any elements e1
and
e2
in the set.
c
- collection whose elements will comprise the new set
ClassCastException
- if the elements in c
are
not Comparable
, or are not mutually comparable
NullPointerException
- if the specified collection is nullpublic TreeSet(SortedSet<E> s)
s
- sorted set whose elements will comprise the new set
NullPointerException
- if the specified sorted set is nullMethod Detail |
---|
public Iterator<E> iterator()
iterator
in interface Iterable<E>
iterator
in interface Collection<E>
iterator
in interface NavigableSet<E>
iterator
in interface Set<E>
iterator
in class AbstractCollection<E>
public Iterator<E> descendingIterator()
descendingIterator
in interface NavigableSet<E>
public NavigableSet<E> descendingSet()
NavigableSet
remove
operation), the results of
the iteration are undefined.
The returned set has an ordering equivalent to
Collections.reverseOrder
(comparator()).
The expression s.descendingSet().descendingSet()
returns a
view of s
essentially equivalent to s
.
descendingSet
in interface NavigableSet<E>
public int size()
size
in interface Collection<E>
size
in interface Set<E>
size
in class AbstractCollection<E>
public boolean isEmpty()
true
if this set contains no elements.
isEmpty
in interface Collection<E>
isEmpty
in interface Set<E>
isEmpty
in class AbstractCollection<E>
true
if this set contains no elementspublic boolean contains(Object o)
true
if this set contains the specified element.
More formally, returns true
if and only if this set
contains an element e
such that
(o==null ? e==null : o.equals(e)).
contains
in interface Collection<E>
contains
in interface Set<E>
contains
in class AbstractCollection<E>
o
- object to be checked for containment in this set
true
if this set contains the specified element
ClassCastException
- if the specified object cannot be compared
with the elements currently in the set
NullPointerException
- if the specified element is null
and this set uses natural ordering, or its comparator
does not permit null elementspublic boolean add(E e)
e
to this set if
the set contains no element e2
such that
(e==null ? e2==null : e.equals(e2)).
If this set already contains the element, the call leaves the set
unchanged and returns false
.
add
in interface Collection<E>
add
in interface Set<E>
add
in class AbstractCollection<E>
e
- element to be added to this set
true
if this set did not already contain the specified
element
ClassCastException
- if the specified object cannot be compared
with the elements currently in this set
NullPointerException
- if the specified element is null
and this set uses natural ordering, or its comparator
does not permit null elementspublic boolean remove(Object o)
e
such that
(o==null ? e==null : o.equals(e)),
if this set contains such an element. Returns true
if
this set contained the element (or equivalently, if this set
changed as a result of the call). (This set will not contain the
element once the call returns.)
remove
in interface Collection<E>
remove
in interface Set<E>
remove
in class AbstractCollection<E>
o
- object to be removed from this set, if present
true
if this set contained the specified element
ClassCastException
- if the specified object cannot be compared
with the elements currently in this set
NullPointerException
- if the specified element is null
and this set uses natural ordering, or its comparator
does not permit null elementspublic void clear()
clear
in interface Collection<E>
clear
in interface Set<E>
clear
in class AbstractCollection<E>
public boolean addAll(Collection<? extends E> c)
addAll
in interface Collection<E>
addAll
in interface Set<E>
addAll
in class AbstractCollection<E>
c
- collection containing elements to be added to this set
true
if this set changed as a result of the call
ClassCastException
- if the elements provided cannot be compared
with the elements currently in the set
NullPointerException
- if the specified collection is null or
if any element is null and this set uses natural ordering, or
its comparator does not permit null elementsAbstractCollection.add(Object)
public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
NavigableSet
fromElement
to toElement
. If fromElement
and
toElement
are equal, the returned set is empty unless fromExclusive
and toExclusive
are both true. The returned set
is backed by this set, so changes in the returned set are reflected in
this set, and vice-versa. The returned set supports all optional set
operations that this set supports.
The returned set will throw an IllegalArgumentException
on an attempt to insert an element outside its range.
subSet
in interface NavigableSet<E>
fromElement
- low endpoint of the returned setfromInclusive
- true
if the low endpoint
is to be included in the returned viewtoElement
- high endpoint of the returned settoInclusive
- true
if the high endpoint
is to be included in the returned view
fromElement
, inclusive, to toElement
, exclusive
ClassCastException
- if fromElement
and
toElement
cannot be compared to one another using this
set's comparator (or, if the set has no comparator, using
natural ordering). Implementations may, but are not required
to, throw this exception if fromElement
or
toElement
cannot be compared to elements currently in
the set.
NullPointerException
- if fromElement
or toElement
is null and this set uses natural ordering, or its comparator
does not permit null elements
IllegalArgumentException
- if fromElement
is
greater than toElement
; or if this set itself
has a restricted range, and fromElement
or
toElement
lies outside the bounds of the range.public NavigableSet<E> headSet(E toElement, boolean inclusive)
NavigableSet
inclusive
is true) toElement
. The
returned set is backed by this set, so changes in the returned set are
reflected in this set, and vice-versa. The returned set supports all
optional set operations that this set supports.
The returned set will throw an IllegalArgumentException
on an attempt to insert an element outside its range.
headSet
in interface NavigableSet<E>
toElement
- high endpoint of the returned setinclusive
- true
if the high endpoint
is to be included in the returned view
inclusive
is true) toElement
ClassCastException
- if toElement
is not compatible
with this set's comparator (or, if the set has no comparator,
if toElement
does not implement Comparable
).
Implementations may, but are not required to, throw this
exception if toElement
cannot be compared to elements
currently in the set.
NullPointerException
- if toElement
is null and
this set uses natural ordering, or its comparator does
not permit null elements
IllegalArgumentException
- if this set itself has a
restricted range, and toElement
lies outside the
bounds of the rangepublic NavigableSet<E> tailSet(E fromElement, boolean inclusive)
NavigableSet
inclusive
is true) fromElement
.
The returned set is backed by this set, so changes in the returned set
are reflected in this set, and vice-versa. The returned set supports
all optional set operations that this set supports.
The returned set will throw an IllegalArgumentException
on an attempt to insert an element outside its range.
tailSet
in interface NavigableSet<E>
fromElement
- low endpoint of the returned setinclusive
- true
if the low endpoint
is to be included in the returned view
fromElement
ClassCastException
- if fromElement
is not compatible
with this set's comparator (or, if the set has no comparator,
if fromElement
does not implement Comparable
).
Implementations may, but are not required to, throw this
exception if fromElement
cannot be compared to elements
currently in the set.
NullPointerException
- if fromElement
is null and
this set uses natural ordering, or its comparator does
not permit null elements
IllegalArgumentException
- if this set itself has a
restricted range, and fromElement
lies outside the
bounds of the rangepublic SortedSet<E> subSet(E fromElement, E toElement)
NavigableSet
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
Equivalent to subSet(fromElement, true, toElement, false)
.
subSet
in interface NavigableSet<E>
subSet
in interface SortedSet<E>
fromElement
- low endpoint (inclusive) of the returned settoElement
- high endpoint (exclusive) of the returned set
ClassCastException
- if fromElement and
toElement cannot be compared to one another using this
set's comparator (or, if the set has no comparator, using
natural ordering). Implementations may, but are not required
to, throw this exception if fromElement or
toElement cannot be compared to elements currently in
the set.
NullPointerException
- if fromElement
or
toElement
is null and this set uses natural ordering,
or its comparator does not permit null elements
IllegalArgumentException
- if fromElement is
greater than toElement; or if this set itself
has a restricted range, and fromElement or
toElement lies outside the bounds of the rangepublic SortedSet<E> headSet(E toElement)
NavigableSet
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
Equivalent to headSet(toElement, false)
.
headSet
in interface NavigableSet<E>
headSet
in interface SortedSet<E>
toElement
- high endpoint (exclusive) of the returned set
ClassCastException
- if toElement is not compatible
with this set's comparator (or, if the set has no comparator,
if toElement does not implement Comparable
).
Implementations may, but are not required to, throw this
exception if toElement cannot be compared to elements
currently in the set.
NullPointerException
- if toElement
is null
and this set uses natural ordering, or its comparator does
not permit null elements
IllegalArgumentException
- if this set itself has a
restricted range, and toElement lies outside the
bounds of the range
napublic SortedSet<E> tailSet(E fromElement)
NavigableSet
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
Equivalent to tailSet(fromElement, true)
.
tailSet
in interface NavigableSet<E>
tailSet
in interface SortedSet<E>
fromElement
- low endpoint (inclusive) of the returned set
ClassCastException
- if fromElement is not compatible
with this set's comparator (or, if the set has no comparator,
if fromElement does not implement Comparable
).
Implementations may, but are not required to, throw this
exception if fromElement cannot be compared to elements
currently in the set.
NullPointerException
- if fromElement
is null
and this set uses natural ordering, or its comparator does
not permit null elements
IllegalArgumentException
- if this set itself has a
restricted range, and fromElement lies outside the
bounds of the rangepublic Comparator<? super E> comparator()
SortedSet
comparator
in interface SortedSet<E>
public E first()
SortedSet
first
in interface SortedSet<E>
NoSuchElementException
- if this set is emptypublic E last()
SortedSet
last
in interface SortedSet<E>
NoSuchElementException
- if this set is emptypublic E lower(E e)
NavigableSet
null
if there is no such element.
lower
in interface NavigableSet<E>
e
- the value to match
e
,
or null
if there is no such element
ClassCastException
- if the specified element cannot be
compared with the elements currently in the set
NullPointerException
- if the specified element is null
and this set uses natural ordering, or its comparator
does not permit null elementspublic E floor(E e)
NavigableSet
null
if there is no such element.
floor
in interface NavigableSet<E>
e
- the value to match
e
,
or null
if there is no such element
ClassCastException
- if the specified element cannot be
compared with the elements currently in the set
NullPointerException
- if the specified element is null
and this set uses natural ordering, or its comparator
does not permit null elementspublic E ceiling(E e)
NavigableSet
null
if there is no such element.
ceiling
in interface NavigableSet<E>
e
- the value to match
e
,
or null
if there is no such element
ClassCastException
- if the specified element cannot be
compared with the elements currently in the set
NullPointerException
- if the specified element is null
and this set uses natural ordering, or its comparator
does not permit null elementspublic E higher(E e)
NavigableSet
null
if there is no such element.
higher
in interface NavigableSet<E>
e
- the value to match
e
,
or null
if there is no such element
ClassCastException
- if the specified element cannot be
compared with the elements currently in the set
NullPointerException
- if the specified element is null
and this set uses natural ordering, or its comparator
does not permit null elementspublic E pollFirst()
NavigableSet
null
if this set is empty.
pollFirst
in interface NavigableSet<E>
null
if this set is emptypublic E pollLast()
NavigableSet
null
if this set is empty.
pollLast
in interface NavigableSet<E>
null
if this set is emptypublic Object clone()
TreeSet
instance. (The elements
themselves are not cloned.)
clone
in class Object
Cloneable
|
Java™ Platform Standard Ed. 6 |
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