TreeSet (Java SE 10 & JDK 10 ) (original) (raw)

Type Parameters:
E - the type of elements maintained by this set
All Implemented Interfaces:
[Serializable](../../java/io/Serializable.html "interface in java.io"), [Cloneable](../../java/lang/Cloneable.html "interface in java.lang"), [Iterable](../../java/lang/Iterable.html "interface in java.lang")<E>, [Collection](../../java/util/Collection.html "interface in java.util")<E>, [NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<E>, [Set](../../java/util/Set.html "interface in java.util")<E>, [SortedSet](../../java/util/SortedSet.html "interface in java.util")<E>

public class TreeSet
extends AbstractSet
implements NavigableSet, Cloneable, Serializable
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 (orcompare) 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 theCollections.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.
Since:
1.2
See Also:
Collection, Set, HashSet, Comparable, Comparator, TreeMap, Serialized Form

Constructor Summary

Constructors

Constructor	Description
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

All Methods Instance Methods Concrete Methods

Modifier and Type	Method	Description
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.
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).
Spliterator<E>	spliterator()	Creates a late-binding and fail-fast Spliterator over the elements in this set.
NavigableSet<E>	subSet(E fromElement, boolean fromInclusive,E toElement, boolean toInclusive)	Returns a view of the portion of this set whose elements range fromfromElement 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 declared in class java.util.[AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")  
   `[containsAll](../../java/util/AbstractCollection.html#containsAll%28java.util.Collection%29), [retainAll](../../java/util/AbstractCollection.html#retainAll%28java.util.Collection%29), [toArray](../../java/util/AbstractCollection.html#toArray%28%29), [toArray](../../java/util/AbstractCollection.html#toArray%28T%5B%5D%29), [toString](../../java/util/AbstractCollection.html#toString%28%29)`  
   * ### Methods declared in class java.util.[AbstractSet](../../java/util/AbstractSet.html "class in java.util")  
   `[equals](../../java/util/AbstractSet.html#equals%28java.lang.Object%29), [hashCode](../../java/util/AbstractSet.html#hashCode%28%29), [removeAll](../../java/util/AbstractSet.html#removeAll%28java.util.Collection%29)`  
   * ### Methods declared in interface java.util.[Collection](../../java/util/Collection.html "interface in java.util")  
   `[parallelStream](../../java/util/Collection.html#parallelStream%28%29), [removeIf](../../java/util/Collection.html#removeIf%28java.util.function.Predicate%29), [stream](../../java/util/Collection.html#stream%28%29)`  
   * ### Methods declared in interface java.lang.[Iterable](../../java/lang/Iterable.html "interface in java.lang")  
   `[forEach](../../java/lang/Iterable.html#forEach%28java.util.function.Consumer%29)`  
   * ### Methods declared in class java.lang.[Object](../../java/lang/Object.html "class in java.lang")  
   `[finalize](../../java/lang/Object.html#finalize%28%29), [getClass](../../java/lang/Object.html#getClass%28%29), [notify](../../java/lang/Object.html#notify%28%29), [notifyAll](../../java/lang/Object.html#notifyAll%28%29), [wait](../../java/lang/Object.html#wait%28%29), [wait](../../java/lang/Object.html#wait%28long%29), [wait](../../java/lang/Object.html#wait%28long,int%29)`  
   * ### Methods declared in interface java.util.[Set](../../java/util/Set.html "interface in java.util")  
   `[containsAll](../../java/util/Set.html#containsAll%28java.util.Collection%29), [equals](../../java/util/Set.html#equals%28java.lang.Object%29), [hashCode](../../java/util/Set.html#hashCode%28%29), [removeAll](../../java/util/Set.html#removeAll%28java.util.Collection%29), [retainAll](../../java/util/Set.html#retainAll%28java.util.Collection%29), [toArray](../../java/util/Set.html#toArray%28%29), [toArray](../../java/util/Set.html#toArray%28T%5B%5D%29)`  
   * ### Methods declared in interface java.util.[SortedSet](../../java/util/SortedSet.html "interface in java.util")  
   `[comparator](../../java/util/SortedSet.html#comparator%28%29)`

Constructor Detail

 * #### TreeSet  
 public TreeSet()  
 Constructs a new, empty tree set, sorted according to the natural ordering of its elements. All elements inserted into the set must implement the [Comparable](../../java/lang/Comparable.html "interface in java.lang") 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`.  
 * #### TreeSet  
 public TreeSet([Comparator](../../java/util/Comparator.html "interface in java.util")<? super [E](../../java/util/TreeSet.html "type parameter in TreeSet")> comparator)  
 Constructs a new, empty tree set, sorted according to the specified comparator. All elements inserted into the set must be _mutually comparable_ by the specified 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`.  
 Parameters:  
 `comparator` \- the comparator that will be used to order this set. If `null`, the [natural ordering](../../java/lang/Comparable.html "interface in java.lang") of the elements will be used.  
 * #### TreeSet  
 public TreeSet([Collection](../../java/util/Collection.html "interface in java.util")<? extends [E](../../java/util/TreeSet.html "type parameter in TreeSet")> c)  
 Constructs a new tree set containing the elements in the specified collection, sorted according to the _natural ordering_ of its elements. All elements inserted into the set must implement the[Comparable](../../java/lang/Comparable.html "interface in java.lang") 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.  
 Parameters:  
 `c` \- collection whose elements will comprise the new set  
 Throws:  
 `[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if the elements in `c` are not [Comparable](../../java/lang/Comparable.html "interface in java.lang"), or are not mutually comparable  
 `[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if the specified collection is null  
 * #### TreeSet  
 public TreeSet([SortedSet](../../java/util/SortedSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")> s)  
 Constructs a new tree set containing the same elements and using the same ordering as the specified sorted set.  
 Parameters:  
 `s` \- sorted set whose elements will comprise the new set  
 Throws:  
 `[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if the specified sorted set is null

Method Detail

* #### iterator  
public [Iterator](../../java/util/Iterator.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")> iterator()  
Returns an iterator over the elements in this set in ascending order.  
Specified by:  
`[iterator](../../java/util/Collection.html#iterator%28%29)` in interface `[Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[iterator](../../java/lang/Iterable.html#iterator%28%29)` in interface `[Iterable](../../java/lang/Iterable.html "interface in java.lang")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[iterator](../../java/util/NavigableSet.html#iterator%28%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[iterator](../../java/util/Set.html#iterator%28%29)` in interface `[Set](../../java/util/Set.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[iterator](../../java/util/AbstractCollection.html#iterator%28%29)` in class `[AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Returns:  
an iterator over the elements in this set in ascending order  
* #### descendingIterator  
public [Iterator](../../java/util/Iterator.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")> descendingIterator()  
Returns an iterator over the elements in this set in descending order.  
Specified by:  
`[descendingIterator](../../java/util/NavigableSet.html#descendingIterator%28%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Returns:  
an iterator over the elements in this set in descending order  
Since:  
1.6  
* #### descendingSet  
public [NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")> descendingSet()  
Returns a reverse order view of the elements contained in this set. The descending set is backed by this set, so changes to the set are reflected in the descending set, and vice-versa. If either set is modified while an iteration over either set is in progress (except through the iterator's own `remove` operation), the results of the iteration are undefined.  
The returned set has an ordering equivalent to[Collections.reverseOrder](../../java/util/Collections.html#reverseOrder%28java.util.Comparator%29)`(comparator())`. The expression `s.descendingSet().descendingSet()` returns a view of `s` essentially equivalent to `s`.  
Specified by:  
`[descendingSet](../../java/util/NavigableSet.html#descendingSet%28%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Returns:  
a reverse order view of this set  
Since:  
1.6  
* #### size  
public int size()  
Returns the number of elements in this set (its cardinality).  
Specified by:  
`[size](../../java/util/Collection.html#size%28%29)` in interface `[Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[size](../../java/util/Set.html#size%28%29)` in interface `[Set](../../java/util/Set.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Returns:  
the number of elements in this set (its cardinality)  
* #### isEmpty  
public boolean isEmpty()  
Returns `true` if this set contains no elements.  
Specified by:  
`[isEmpty](../../java/util/Collection.html#isEmpty%28%29)` in interface `[Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[isEmpty](../../java/util/Set.html#isEmpty%28%29)` in interface `[Set](../../java/util/Set.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Overrides:  
`[isEmpty](../../java/util/AbstractCollection.html#isEmpty%28%29)` in class `[AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Returns:  
`true` if this set contains no elements  
* #### contains  
public boolean contains([Object](../../java/lang/Object.html "class in java.lang") o)  
Returns `true` if this set contains the specified element. More formally, returns `true` if and only if this set contains an element `e` such that`Objects.equals(o, e)`.  
Specified by:  
`[contains](../../java/util/Collection.html#contains%28java.lang.Object%29)` in interface `[Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[contains](../../java/util/Set.html#contains%28java.lang.Object%29)` in interface `[Set](../../java/util/Set.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Overrides:  
`[contains](../../java/util/AbstractCollection.html#contains%28java.lang.Object%29)` in class `[AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`o` \- object to be checked for containment in this set  
Returns:  
`true` if this set contains the specified element  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if the specified object cannot be compared with the elements currently in the set  
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements  
* #### add  
public boolean add([E](../../java/util/TreeSet.html "type parameter in TreeSet") e)  
Adds the specified element to this set if it is not already present. More formally, adds the specified element `e` to this set if the set contains no element `e2` such that`Objects.equals(e, e2)`. If this set already contains the element, the call leaves the set unchanged and returns `false`.  
Specified by:  
`[add](../../java/util/Collection.html#add%28E%29)` in interface `[Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[add](../../java/util/Set.html#add%28E%29)` in interface `[Set](../../java/util/Set.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Overrides:  
`[add](../../java/util/AbstractCollection.html#add%28E%29)` in class `[AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`e` \- element to be added to this set  
Returns:  
`true` if this set did not already contain the specified element  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if the specified object cannot be compared with the elements currently in this set  
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements  
* #### remove  
public boolean remove([Object](../../java/lang/Object.html "class in java.lang") o)  
Removes the specified element from this set if it is present. More formally, removes an element `e` such that`Objects.equals(o, 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.)  
Specified by:  
`[remove](../../java/util/Collection.html#remove%28java.lang.Object%29)` in interface `[Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[remove](../../java/util/Set.html#remove%28java.lang.Object%29)` in interface `[Set](../../java/util/Set.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Overrides:  
`[remove](../../java/util/AbstractCollection.html#remove%28java.lang.Object%29)` in class `[AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`o` \- object to be removed from this set, if present  
Returns:  
`true` if this set contained the specified element  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if the specified object cannot be compared with the elements currently in this set  
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements  
* #### clear  
public void clear()  
Removes all of the elements from this set. The set will be empty after this call returns.  
Specified by:  
`[clear](../../java/util/Collection.html#clear%28%29)` in interface `[Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[clear](../../java/util/Set.html#clear%28%29)` in interface `[Set](../../java/util/Set.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Overrides:  
`[clear](../../java/util/AbstractCollection.html#clear%28%29)` in class `[AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
* #### addAll  
public boolean addAll([Collection](../../java/util/Collection.html "interface in java.util")<? extends [E](../../java/util/TreeSet.html "type parameter in TreeSet")> c)  
Adds all of the elements in the specified collection to this set.  
Specified by:  
`[addAll](../../java/util/Collection.html#addAll%28java.util.Collection%29)` in interface `[Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[addAll](../../java/util/Set.html#addAll%28java.util.Collection%29)` in interface `[Set](../../java/util/Set.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Overrides:  
`[addAll](../../java/util/AbstractCollection.html#addAll%28java.util.Collection%29)` in class `[AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`c` \- collection containing elements to be added to this set  
Returns:  
`true` if this set changed as a result of the call  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if the elements provided cannot be compared with the elements currently in the set  
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- 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 elements  
See Also:  
[AbstractCollection.add(Object)](../../java/util/AbstractCollection.html#add%28E%29)  
* #### subSet  
public [NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")> subSet([E](../../java/util/TreeSet.html "type parameter in TreeSet") fromElement,  
                              boolean fromInclusive,  
                              [E](../../java/util/TreeSet.html "type parameter in TreeSet") toElement,  
                              boolean toInclusive)  
Returns a view of the portion of this set whose elements range from`fromElement` to `toElement`. If `fromElement` and`toElement` are equal, the returned set is empty unless ` fromInclusive` and `toInclusive` 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.  
Specified by:  
`[subSet](../../java/util/NavigableSet.html#subSet%28E,boolean,E,boolean%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`fromElement` \- low endpoint of the returned set  
`fromInclusive` \- `true` if the low endpoint is to be included in the returned view  
`toElement` \- high endpoint of the returned set  
`toInclusive` \- `true` if the high endpoint is to be included in the returned view  
Returns:  
a view of the portion of this set whose elements range from`fromElement`, inclusive, to `toElement`, exclusive  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- 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](../../java/lang/NullPointerException.html "class in java.lang")` \- if `fromElement` or `toElement` is null and this set uses natural ordering, or its comparator does not permit null elements  
`[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang")` \- 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.  
Since:  
1.6  
* #### headSet  
public [NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")> headSet([E](../../java/util/TreeSet.html "type parameter in TreeSet") 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`. 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.  
Specified by:  
`[headSet](../../java/util/NavigableSet.html#headSet%28E,boolean%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`toElement` \- high endpoint of the returned set  
`inclusive` \- `true` if the high endpoint is to be included in the returned view  
Returns:  
a view of the portion of this set whose elements are less than (or equal to, if `inclusive` is true) `toElement`  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if `toElement` is not compatible with this set's comparator (or, if the set has no comparator, if `toElement` does not implement [Comparable](../../java/lang/Comparable.html "interface in java.lang")). Implementations may, but are not required to, throw this exception if `toElement` cannot be compared to elements currently in the set.  
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if `toElement` is null and this set uses natural ordering, or its comparator does not permit null elements  
`[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if this set itself has a restricted range, and `toElement` lies outside the bounds of the range  
Since:  
1.6  
* #### tailSet  
public [NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")> tailSet([E](../../java/util/TreeSet.html "type parameter in TreeSet") 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`. 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.  
Specified by:  
`[tailSet](../../java/util/NavigableSet.html#tailSet%28E,boolean%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`fromElement` \- low endpoint of the returned set  
`inclusive` \- `true` if the low endpoint is to be included in the returned view  
Returns:  
a view of the portion of this set whose elements are greater than or equal to `fromElement`  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if `fromElement` is not compatible with this set's comparator (or, if the set has no comparator, if `fromElement` does not implement [Comparable](../../java/lang/Comparable.html "interface in java.lang")). Implementations may, but are not required to, throw this exception if `fromElement` cannot be compared to elements currently in the set.  
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if `fromElement` is null and this set uses natural ordering, or its comparator does not permit null elements  
`[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if this set itself has a restricted range, and `fromElement` lies outside the bounds of the range  
Since:  
1.6  
* #### subSet  
public [SortedSet](../../java/util/SortedSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")> subSet([E](../../java/util/TreeSet.html "type parameter in TreeSet") fromElement,  
                           [E](../../java/util/TreeSet.html "type parameter in TreeSet") toElement)  
Returns a view of the portion of this set whose elements range from `fromElement`, inclusive, to `toElement`, exclusive. (If `fromElement` and `toElement` are equal, the returned set is empty.) 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.  
Equivalent to `subSet(fromElement, true, toElement, false)`.  
Specified by:  
`[subSet](../../java/util/NavigableSet.html#subSet%28E,E%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[subSet](../../java/util/SortedSet.html#subSet%28E,E%29)` in interface `[SortedSet](../../java/util/SortedSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`fromElement` \- low endpoint (inclusive) of the returned set  
`toElement` \- high endpoint (exclusive) of the returned set  
Returns:  
a view of the portion of this set whose elements range from`fromElement`, inclusive, to `toElement`, exclusive  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- 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](../../java/lang/NullPointerException.html "class in java.lang")` \- if `fromElement` or`toElement` is null and this set uses natural ordering, or its comparator does not permit null elements  
`[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang")` \- 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  
* #### headSet  
public [SortedSet](../../java/util/SortedSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")> headSet([E](../../java/util/TreeSet.html "type parameter in TreeSet") toElement)  
Returns a view of the portion of this set whose elements are strictly less than `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.  
Equivalent to `headSet(toElement, false)`.  
Specified by:  
`[headSet](../../java/util/NavigableSet.html#headSet%28E%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[headSet](../../java/util/SortedSet.html#headSet%28E%29)` in interface `[SortedSet](../../java/util/SortedSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`toElement` \- high endpoint (exclusive) of the returned set  
Returns:  
a view of the portion of this set whose elements are strictly less than `toElement`  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if `toElement` is not compatible with this set's comparator (or, if the set has no comparator, if `toElement` does not implement [Comparable](../../java/lang/Comparable.html "interface in java.lang")). Implementations may, but are not required to, throw this exception if `toElement` cannot be compared to elements currently in the set.  
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if `toElement` is null and this set uses natural ordering, or its comparator does not permit null elements  
`[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if this set itself has a restricted range, and `toElement` lies outside the bounds of the range  
* #### tailSet  
public [SortedSet](../../java/util/SortedSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")> tailSet([E](../../java/util/TreeSet.html "type parameter in TreeSet") fromElement)  
Returns a view of the portion of this set whose elements are greater than or equal to `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.  
Equivalent to `tailSet(fromElement, true)`.  
Specified by:  
`[tailSet](../../java/util/NavigableSet.html#tailSet%28E%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[tailSet](../../java/util/SortedSet.html#tailSet%28E%29)` in interface `[SortedSet](../../java/util/SortedSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`fromElement` \- low endpoint (inclusive) of the returned set  
Returns:  
a view of the portion of this set whose elements are greater than or equal to `fromElement`  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if `fromElement` is not compatible with this set's comparator (or, if the set has no comparator, if `fromElement` does not implement [Comparable](../../java/lang/Comparable.html "interface in java.lang")). Implementations may, but are not required to, throw this exception if `fromElement` cannot be compared to elements currently in the set.  
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if `fromElement` is null and this set uses natural ordering, or its comparator does not permit null elements  
`[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if this set itself has a restricted range, and `fromElement` lies outside the bounds of the range  
* #### first  
public [E](../../java/util/TreeSet.html "type parameter in TreeSet") first()  
Description copied from interface: `[SortedSet](../../java/util/SortedSet.html#first%28%29)`  
Returns the first (lowest) element currently in this set.  
Specified by:  
`[first](../../java/util/SortedSet.html#first%28%29)` in interface `[SortedSet](../../java/util/SortedSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Returns:  
the first (lowest) element currently in this set  
Throws:  
`[NoSuchElementException](../../java/util/NoSuchElementException.html "class in java.util")` \- if this set is empty  
* #### last  
public [E](../../java/util/TreeSet.html "type parameter in TreeSet") last()  
Description copied from interface: `[SortedSet](../../java/util/SortedSet.html#last%28%29)`  
Returns the last (highest) element currently in this set.  
Specified by:  
`[last](../../java/util/SortedSet.html#last%28%29)` in interface `[SortedSet](../../java/util/SortedSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Returns:  
the last (highest) element currently in this set  
Throws:  
`[NoSuchElementException](../../java/util/NoSuchElementException.html "class in java.util")` \- if this set is empty  
* #### lower  
public [E](../../java/util/TreeSet.html "type parameter in TreeSet") lower([E](../../java/util/TreeSet.html "type parameter in TreeSet") e)  
Returns the greatest element in this set strictly less than the given element, or `null` if there is no such element.  
Specified by:  
`[lower](../../java/util/NavigableSet.html#lower%28E%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`e` \- the value to match  
Returns:  
the greatest element less than `e`, or `null` if there is no such element  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if the specified element cannot be compared with the elements currently in the set  
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements  
Since:  
1.6  
* #### floor  
public [E](../../java/util/TreeSet.html "type parameter in TreeSet") floor([E](../../java/util/TreeSet.html "type parameter in TreeSet") e)  
Returns the greatest element in this set less than or equal to the given element, or `null` if there is no such element.  
Specified by:  
`[floor](../../java/util/NavigableSet.html#floor%28E%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`e` \- the value to match  
Returns:  
the greatest element less than or equal to `e`, or `null` if there is no such element  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if the specified element cannot be compared with the elements currently in the set  
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements  
Since:  
1.6  
* #### ceiling  
public [E](../../java/util/TreeSet.html "type parameter in TreeSet") ceiling([E](../../java/util/TreeSet.html "type parameter in TreeSet") e)  
Returns the least element in this set greater than or equal to the given element, or `null` if there is no such element.  
Specified by:  
`[ceiling](../../java/util/NavigableSet.html#ceiling%28E%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`e` \- the value to match  
Returns:  
the least element greater than or equal to `e`, or `null` if there is no such element  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if the specified element cannot be compared with the elements currently in the set  
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements  
Since:  
1.6  
* #### higher  
public [E](../../java/util/TreeSet.html "type parameter in TreeSet") higher([E](../../java/util/TreeSet.html "type parameter in TreeSet") e)  
Returns the least element in this set strictly greater than the given element, or `null` if there is no such element.  
Specified by:  
`[higher](../../java/util/NavigableSet.html#higher%28E%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Parameters:  
`e` \- the value to match  
Returns:  
the least element greater than `e`, or `null` if there is no such element  
Throws:  
`[ClassCastException](../../java/lang/ClassCastException.html "class in java.lang")` \- if the specified element cannot be compared with the elements currently in the set  
`[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements  
Since:  
1.6  
* #### pollFirst  
public [E](../../java/util/TreeSet.html "type parameter in TreeSet") pollFirst()  
Retrieves and removes the first (lowest) element, or returns `null` if this set is empty.  
Specified by:  
`[pollFirst](../../java/util/NavigableSet.html#pollFirst%28%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Returns:  
the first element, or `null` if this set is empty  
Since:  
1.6  
* #### pollLast  
public [E](../../java/util/TreeSet.html "type parameter in TreeSet") pollLast()  
Retrieves and removes the last (highest) element, or returns `null` if this set is empty.  
Specified by:  
`[pollLast](../../java/util/NavigableSet.html#pollLast%28%29)` in interface `[NavigableSet](../../java/util/NavigableSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Returns:  
the last element, or `null` if this set is empty  
Since:  
1.6  
* #### clone  
public [Object](../../java/lang/Object.html "class in java.lang") clone()  
Returns a shallow copy of this `TreeSet` instance. (The elements themselves are not cloned.)  
Overrides:  
`[clone](../../java/lang/Object.html#clone%28%29)` in class `[Object](../../java/lang/Object.html "class in java.lang")`  
Returns:  
a shallow copy of this set  
See Also:  
[Cloneable](../../java/lang/Cloneable.html "interface in java.lang")  
* #### spliterator  
public [Spliterator](../../java/util/Spliterator.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")> spliterator()  
Specified by:  
`[spliterator](../../java/util/Collection.html#spliterator%28%29)` in interface `[Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[spliterator](../../java/lang/Iterable.html#spliterator%28%29)` in interface `[Iterable](../../java/lang/Iterable.html "interface in java.lang")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[spliterator](../../java/util/Set.html#spliterator%28%29)` in interface `[Set](../../java/util/Set.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Specified by:  
`[spliterator](../../java/util/SortedSet.html#spliterator%28%29)` in interface `[SortedSet](../../java/util/SortedSet.html "interface in java.util")<[E](../../java/util/TreeSet.html "type parameter in TreeSet")>`  
Returns:  
a `Spliterator` over the elements in this set  
Since:  
1.8

TreeSet (Java SE 10 & JDK 10 ) (original) (raw)

Constructor Summary

Method Summary

Constructor Detail

Method Detail