Class TreeSet<E>

java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractSet<E>
java.util.TreeSet<E>
Type Parameters:
E - the type of elements maintained by this set
All Implemented Interfaces:
Serializable,Cloneable,Iterable<E>,Collection<E>,NavigableSet<E>,SequencedCollection<E>,SequencedSet<E>,Set<E>,SortedSet<E>
public classTreeSet<E>extendsAbstractSet<E>implementsNavigableSet<E>,Cloneable,Serializable
ANavigableSet implementation based on aTreeMap. The elements are ordered using theirnatural ordering, or by aComparator 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 andcontains).

Note that the ordering maintained by a set (whether or not an explicit comparator is provided) must beconsistent with equals if it is to correctly implement theSet interface. (SeeComparable orComparator for a precise definition ofconsistent with equals.) This is so because theSet interface is defined in terms of theequals operation, but aTreeSet instance performs all element comparisons using itscompareTo (orcompare) method, so two elements that are deemed equal by this method are, from the standpoint of the set, equal. The behavior of a setis well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of theSet 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, itmust 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'siterator method arefail-fast: if the set is modified at any time after the iterator is created, in any way except through the iterator's ownremove method, the iterator will throw aConcurrentModificationException. 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 throwConcurrentModificationException 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.

TheaddFirst andaddLast methods of this class throwUnsupportedOperationException. The encounter order of elements is determined by the comparison method; therefore, explicit positioning is not supported.

This class is a member of the Java Collections Framework.

Since:
1.2
See Also:

  • Constructor Summary

    Constructors
    Constructor
    Description
    Constructs a new, empty tree set, sorted according to the natural ordering of its elements.
    TreeSet(Collection<? extendsE> c)
    Constructs a new tree set containing the elements in the specified collection, sorted according to thenatural ordering of its elements.
    TreeSet(Comparator<? superE> comparator)
    Constructs a new, empty tree set, sorted according to the specified comparator.
    Constructs a new tree set containing the same elements and using the same ordering as the specified sorted set.

  • Method Summary

    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<? extendsE> c)
    Adds all of the elements in the specified collection to this set.
    void
    ThrowsUnsupportedOperationException.
    void
    ThrowsUnsupportedOperationException.
    Returns the least element in this set greater than or equal to the given element, ornull if there is no such element.
    void
    Removes all of the elements from this set.
    Returns a shallow copy of thisTreeSet instance.
    Comparator<? superE>
    Returns the comparator used to order the elements in this set, ornull if this set uses thenatural ordering of its elements.
    boolean
    Returnstrue if this set contains the specified element.
    Returns an iterator over the elements in this set in descending order.
    Returns a reverse order view of the elements contained in this set.
    Returns the first (lowest) element currently in this set.
    floor(E e)
    Returns the greatest element in this set less than or equal to the given element, ornull if there is no such element.
    headSet(E toElement)
    Returns a view of the portion of this set whose elements are strictly less thantoElement.
    headSet(E toElement, boolean inclusive)
    Returns a view of the portion of this set whose elements are less than (or equal to, ifinclusive is true)toElement.
    higher(E e)
    Returns the least element in this set strictly greater than the given element, ornull if there is no such element.
    boolean
    Returnstrue if this set contains no elements.
    Returns an iterator over the elements in this set in ascending order.
    Returns the last (highest) element currently in this set.
    lower(E e)
    Returns the greatest element in this set strictly less than the given element, ornull if there is no such element.
    Retrieves and removes the first (lowest) element, or returnsnull if this set is empty (optional operation).
    Retrieves and removes the last (highest) element, or returnsnull if this set is empty (optional operation).
    boolean
    Removes the specified element from this set if it is present.
    int
    Returns the number of elements in this set (its cardinality).
    Creates alate-binding andfail-fastSpliterator over the elements in this set.
    subSet(E fromElement, boolean fromInclusive,E toElement, boolean toInclusive)
    Returns a view of the portion of this set whose elements range fromfromElement totoElement.
    subSet(E fromElement,E toElement)
    Returns a view of the portion of this set whose elements range fromfromElement, inclusive, totoElement, exclusive.
    tailSet(E fromElement)
    Returns a view of the portion of this set whose elements are greater than or equal tofromElement.
    tailSet(E fromElement, boolean inclusive)
    Returns a view of the portion of this set whose elements are greater than (or equal to, ifinclusive is true)fromElement.

    Methods declared in class java.util.AbstractSet

    equals,hashCode,removeAll

    Methods declared in class java.util.AbstractCollection

    containsAll,retainAll,toArray,toArray,toString

    Methods declared in class java.lang.Object

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

    Methods declared in interface java.util.Collection

    parallelStream,removeIf,stream,toArray

    Methods declared in interface java.lang.Iterable

    forEach

    Methods declared in interface java.util.NavigableSet

    removeFirst,removeLast,reversed

    Methods declared in interface java.util.Set

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

    Methods declared in interface java.util.SortedSet

    getFirst,getLast

  • Constructor Details

    • 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 theComparable interface. Furthermore, all such elements must bemutually comparable:e1.compareTo(e2) must not throw aClassCastException for any elementse1 ande2 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), theadd call will throw aClassCastException.

    • TreeSet

      public TreeSet(Comparator<? superE> comparator)
      Constructs a new, empty tree set, sorted according to the specified comparator. All elements inserted into the set must bemutually comparable by the specified comparator:comparator.compare(e1, e2) must not throw aClassCastException for any elementse1 ande2 in the set. If the user attempts to add an element to the set that violates this constraint, theadd call will throw aClassCastException.
      Parameters:
      comparator - the comparator that will be used to order this set. Ifnull, thenatural ordering of the elements will be used.

    • TreeSet

      public TreeSet(Collection<? extendsE> c)
      Constructs a new tree set containing the elements in the specified collection, sorted according to thenatural ordering of its elements. All elements inserted into the set must implement theComparable interface. Furthermore, all such elements must bemutually comparable:e1.compareTo(e2) must not throw aClassCastException for any elementse1 ande2 in the set.
      Parameters:
      c - collection whose elements will comprise the new set
      Throws:
      ClassCastException - if the elements inc are notComparable, or are not mutually comparable
      NullPointerException - if the specified collection is null

    • TreeSet

      public TreeSet(SortedSet<E> 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 - if the specified sorted set is null

  • Method Details

    • iterator

      public Iterator<E> iterator()
      Returns an iterator over the elements in this set in ascending order.
      Specified by:
      iterator in interface Collection<E>
      Specified by:
      iterator in interface Iterable<E>
      Specified by:
      iterator in interface NavigableSet<E>
      Specified by:
      iterator in interface Set<E>
      Specified by:
      iterator in class AbstractCollection<E>
      Returns:
      an iterator over the elements in this set in ascending order

    • descendingIterator

      public Iterator<E> descendingIterator()
      Returns an iterator over the elements in this set in descending order.
      Specified by:
      descendingIterator in interface NavigableSet<E>
      Returns:
      an iterator over the elements in this set in descending order
      Since:
      1.6

    • descendingSet

      public NavigableSet<E> descendingSet()
      Description copied from interface: NavigableSet
      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 ownremove operation), the results of the iteration are undefined.

      The returned set has an ordering equivalent toCollections.reverseOrder(comparator()). The expressions.descendingSet().descendingSet() returns a view ofs essentially equivalent tos.

      Specified by:
      descendingSet in interface NavigableSet<E>
      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 in interface Collection<E>
      Specified by:
      size in interface Set<E>
      Returns:
      the number of elements in this set (its cardinality)

    • isEmpty

      public boolean isEmpty()
      Returnstrue if this set contains no elements.
      Specified by:
      isEmpty in interface Collection<E>
      Specified by:
      isEmpty in interface Set<E>
      Overrides:
      isEmpty in class AbstractCollection<E>
      Returns:
      true if this set contains no elements

    • contains

      public boolean contains(Object o)
      Returnstrue if this set contains the specified element. More formally, returnstrue if and only if this set contains an elemente such thatObjects.equals(o, e).
      Specified by:
      contains in interface Collection<E>
      Specified by:
      contains in interface Set<E>
      Overrides:
      contains in class AbstractCollection<E>
      Parameters:
      o - object to be checked for containment in this set
      Returns:
      true if this set contains the specified element
      Throws:
      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 elements

    • add

      public boolean add(E e)
      Adds the specified element to this set if it is not already present. More formally, adds the specified elemente to this set if the set contains no elemente2 such thatObjects.equals(e, e2). If this set already contains the element, the call leaves the set unchanged and returnsfalse.
      Specified by:
      add in interface Collection<E>
      Specified by:
      add in interface Set<E>
      Overrides:
      add in class AbstractCollection<E>
      Parameters:
      e - element to be added to this set
      Returns:
      true if this set did not already contain the specified element
      Throws:
      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 elements

    • remove

      public boolean remove(Object o)
      Removes the specified element from this set if it is present. More formally, removes an elemente such thatObjects.equals(o, e), if this set contains such an element. Returnstrue 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 in interface Collection<E>
      Specified by:
      remove in interface Set<E>
      Overrides:
      remove in class AbstractCollection<E>
      Parameters:
      o - object to be removed from this set, if present
      Returns:
      true if this set contained the specified element
      Throws:
      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 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 in interface Collection<E>
      Specified by:
      clear in interface Set<E>
      Overrides:
      clear in class AbstractCollection<E>

    • addAll

      public boolean addAll(Collection<? extendsE> c)
      Adds all of the elements in the specified collection to this set.
      Specified by:
      addAll in interface Collection<E>
      Specified by:
      addAll in interface Set<E>
      Overrides:
      addAll in class AbstractCollection<E>
      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 - 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 elements
      See Also:

    • subSet

      public NavigableSet<E> subSet(E fromElement, boolean fromInclusive,E toElement, boolean toInclusive)
      Description copied from interface: NavigableSet
      Returns a view of the portion of this set whose elements range fromfromElement totoElement. IffromElement andtoElement are equal, the returned set is empty unless fromInclusive andtoInclusive 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 anIllegalArgumentException on an attempt to insert an element outside its range.

      Specified by:
      subSet in interface NavigableSet<E>
      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 fromfromElement, inclusive, totoElement, exclusive
      Throws:
      ClassCastException - iffromElement andtoElement 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 iffromElement ortoElement cannot be compared to elements currently in the set.
      NullPointerException - iffromElement ortoElement is null and this set uses natural ordering, or its comparator does not permit null elements
      IllegalArgumentException - iffromElement is greater thantoElement; or if this set itself has a restricted range, andfromElement ortoElement lies outside the bounds of the range.
      Since:
      1.6

    • headSet

      public NavigableSet<E> headSet(E toElement, boolean inclusive)
      Description copied from interface: NavigableSet
      Returns a view of the portion of this set whose elements are less than (or equal to, ifinclusive 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 anIllegalArgumentException on an attempt to insert an element outside its range.

      Specified by:
      headSet in interface NavigableSet<E>
      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, ifinclusive is true)toElement
      Throws:
      ClassCastException - iftoElement is not compatible with this set's comparator (or, if the set has no comparator, iftoElement does not implementComparable). Implementations may, but are not required to, throw this exception iftoElement cannot be compared to elements currently in the set.
      NullPointerException - iftoElement 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, andtoElement lies outside the bounds of the range
      Since:
      1.6

    • tailSet

      public NavigableSet<E> tailSet(E fromElement, boolean inclusive)
      Description copied from interface: NavigableSet
      Returns a view of the portion of this set whose elements are greater than (or equal to, ifinclusive 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 anIllegalArgumentException on an attempt to insert an element outside its range.

      Specified by:
      tailSet in interface NavigableSet<E>
      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 tofromElement
      Throws:
      ClassCastException - iffromElement is not compatible with this set's comparator (or, if the set has no comparator, iffromElement does not implementComparable). Implementations may, but are not required to, throw this exception iffromElement cannot be compared to elements currently in the set.
      NullPointerException - iffromElement 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, andfromElement lies outside the bounds of the range
      Since:
      1.6

    • subSet

      public SortedSet<E> subSet(E fromElement,E toElement)
      Description copied from interface: NavigableSet
      Returns a view of the portion of this set whose elements range fromfromElement, inclusive, totoElement, exclusive. (IffromElement andtoElement 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 anIllegalArgumentException on an attempt to insert an element outside its range.

      Equivalent tosubSet(fromElement, true, toElement, false).

      Specified by:
      subSet in interface NavigableSet<E>
      Specified by:
      subSet in interface SortedSet<E>
      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 fromfromElement, inclusive, totoElement, exclusive
      Throws:
      ClassCastException - iffromElement andtoElement 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 iffromElement ortoElement cannot be compared to elements currently in the set.
      NullPointerException - iffromElement ortoElement is null and this set uses natural ordering, or its comparator does not permit null elements
      IllegalArgumentException - iffromElement is greater thantoElement; or if this set itself has a restricted range, andfromElement ortoElement lies outside the bounds of the range

    • headSet

      public SortedSet<E> headSet(E toElement)
      Description copied from interface: NavigableSet
      Returns a view of the portion of this set whose elements are strictly less thantoElement. 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 anIllegalArgumentException on an attempt to insert an element outside its range.

      Equivalent toheadSet(toElement, false).

      Specified by:
      headSet in interface NavigableSet<E>
      Specified by:
      headSet in interface SortedSet<E>
      Parameters:
      toElement - high endpoint (exclusive) of the returned set
      Returns:
      a view of the portion of this set whose elements are strictly less thantoElement
      Throws:
      ClassCastException - iftoElement is not compatible with this set's comparator (or, if the set has no comparator, iftoElement does not implementComparable). Implementations may, but are not required to, throw this exception iftoElement cannot be compared to elements currently in the set.
      NullPointerException - iftoElement 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, andtoElement lies outside the bounds of the range

    • tailSet

      public SortedSet<E> tailSet(E fromElement)
      Description copied from interface: NavigableSet
      Returns a view of the portion of this set whose elements are greater than or equal tofromElement. 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 anIllegalArgumentException on an attempt to insert an element outside its range.

      Equivalent totailSet(fromElement, true).

      Specified by:
      tailSet in interface NavigableSet<E>
      Specified by:
      tailSet in interface SortedSet<E>
      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 tofromElement
      Throws:
      ClassCastException - iffromElement is not compatible with this set's comparator (or, if the set has no comparator, iffromElement does not implementComparable). Implementations may, but are not required to, throw this exception iffromElement cannot be compared to elements currently in the set.
      NullPointerException - iffromElement 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, andfromElement lies outside the bounds of the range

    • comparator

      public Comparator<? superE> comparator()
      Description copied from interface: SortedSet
      Returns the comparator used to order the elements in this set, ornull if this set uses thenatural ordering of its elements.
      Specified by:
      comparator in interface SortedSet<E>
      Returns:
      the comparator used to order the elements in this set, ornull if this set uses the natural ordering of its elements

    • first

      public E first()
      Description copied from interface: SortedSet
      Returns the first (lowest) element currently in this set.
      Specified by:
      first in interface SortedSet<E>
      Returns:
      the first (lowest) element currently in this set
      Throws:
      NoSuchElementException - if this set is empty

    • last

      public E last()
      Description copied from interface: SortedSet
      Returns the last (highest) element currently in this set.
      Specified by:
      last in interface SortedSet<E>
      Returns:
      the last (highest) element currently in this set
      Throws:
      NoSuchElementException - if this set is empty

    • lower

      public E lower(E e)
      Description copied from interface: NavigableSet
      Returns the greatest element in this set strictly less than the given element, ornull if there is no such element.
      Specified by:
      lower in interface NavigableSet<E>
      Parameters:
      e - the value to match
      Returns:
      the greatest element less thane, ornull if there is no such element
      Throws:
      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 elements
      Since:
      1.6

    • floor

      public E floor(E e)
      Description copied from interface: NavigableSet
      Returns the greatest element in this set less than or equal to the given element, ornull if there is no such element.
      Specified by:
      floor in interface NavigableSet<E>
      Parameters:
      e - the value to match
      Returns:
      the greatest element less than or equal toe, ornull if there is no such element
      Throws:
      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 elements
      Since:
      1.6

    • ceiling

      public E ceiling(E e)
      Description copied from interface: NavigableSet
      Returns the least element in this set greater than or equal to the given element, ornull if there is no such element.
      Specified by:
      ceiling in interface NavigableSet<E>
      Parameters:
      e - the value to match
      Returns:
      the least element greater than or equal toe, ornull if there is no such element
      Throws:
      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 elements
      Since:
      1.6

    • higher

      public E higher(E e)
      Description copied from interface: NavigableSet
      Returns the least element in this set strictly greater than the given element, ornull if there is no such element.
      Specified by:
      higher in interface NavigableSet<E>
      Parameters:
      e - the value to match
      Returns:
      the least element greater thane, ornull if there is no such element
      Throws:
      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 elements
      Since:
      1.6

    • pollFirst

      public E pollFirst()
      Description copied from interface: NavigableSet
      Retrieves and removes the first (lowest) element, or returnsnull if this set is empty (optional operation).
      Specified by:
      pollFirst in interface NavigableSet<E>
      Returns:
      the first element, ornull if this set is empty
      Since:
      1.6

    • pollLast

      public E pollLast()
      Description copied from interface: NavigableSet
      Retrieves and removes the last (highest) element, or returnsnull if this set is empty (optional operation).
      Specified by:
      pollLast in interface NavigableSet<E>
      Returns:
      the last element, ornull if this set is empty
      Since:
      1.6

    • addFirst

      public void addFirst(E e)
      ThrowsUnsupportedOperationException. The encounter order induced by this set's comparison method determines the position of elements, so explicit positioning is not supported.
      Specified by:
      addFirst in interface SequencedCollection<E>
      Specified by:
      addFirst in interface SortedSet<E>
      Parameters:
      e - the element to be added
      Throws:
      UnsupportedOperationException - always
      Since:
      21

    • addLast

      public void addLast(E e)
      ThrowsUnsupportedOperationException. The encounter order induced by this set's comparison method determines the position of elements, so explicit positioning is not supported.
      Specified by:
      addLast in interface SequencedCollection<E>
      Specified by:
      addLast in interface SortedSet<E>
      Parameters:
      e - the element to be added.
      Throws:
      UnsupportedOperationException - always
      Since:
      21

    • clone

      public Object clone()
      Returns a shallow copy of thisTreeSet instance. (The elements themselves are not cloned.)
      Overrides:
      clone in class Object
      Returns:
      a shallow copy of this set
      See Also:

    • spliterator

      public Spliterator<E> spliterator()
      Creates alate-binding andfail-fastSpliterator over the elements in this set.

      TheSpliterator reportsSpliterator.SIZED,Spliterator.DISTINCT,Spliterator.SORTED, andSpliterator.ORDERED. Overriding implementations should document the reporting of additional characteristic values.

      The spliterator's comparator (seeSpliterator.getComparator()) isnull if the tree set's comparator (seecomparator()) isnull. Otherwise, the spliterator's comparator is the same as or imposes the same total ordering as the tree set's comparator.

      Specified by:
      spliterator in interface Collection<E>
      Specified by:
      spliterator in interface Iterable<E>
      Specified by:
      spliterator in interface Set<E>
      Specified by:
      spliterator in interface SortedSet<E>
      Returns:
      aSpliterator over the elements in this set
      Since:
      1.8