ConcurrentSkipListSet

public class ConcurrentSkipListSet extends AbstractSet<E>
implements NavigableSet<E> Cloneable Serializable

A scalable concurrent NavigableSet implementation based on a ConcurrentSkipListMap. The elements of the set are kept sorted according to their {@linkplain Comparable natural ordering}, or by a Comparator provided at set creation time, depending on which constructor is used.

This implementation provides expected average log(n) time cost for the contains, add, and remove operations and their variants. Insertion, removal, and access operations safely execute concurrently by multiple threads.

Iterators and spliterators are weakly consistent.

Ascending ordered views and their iterators are faster than descending ones.

Beware that, unlike in most collections, the size method is not a constant-time operation. Because of the asynchronous nature of these sets, determining the current number of elements requires a traversal of the elements, and so may report inaccurate results if this collection is modified during traversal. Additionally, the bulk operations addAll, removeAll, retainAll, containsAll, equals, and toArray are not guaranteed to be performed atomically. For example, an iterator operating concurrently with an addAll operation might view only some of the added elements.

This class and its iterators implement all of the optional methods of the Set and Iterator interfaces. Like most other concurrent collection implementations, this class does not permit the use of null elements, because null arguments and return values cannot be reliably distinguished from the absence of elements.

Public Constructor Summary

	ConcurrentSkipListSet() Constructs a new, empty set that orders its elements according to their {@linkplain Comparable natural ordering}.
	ConcurrentSkipListSet(Comparator<? super E> comparator) Constructs a new, empty set that orders its elements according to the specified comparator.
	ConcurrentSkipListSet(Collection<? extends E> c) Constructs a new set containing the elements in the specified collection, that orders its elements according to their {@linkplain Comparable natural ordering}.
	ConcurrentSkipListSet(SortedSet<E> s) Constructs a new set containing the same elements and using the same ordering as the specified sorted set.

Public Method Summary

boolean	add(E e) Adds the specified element to this set if it is not already present.
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.
ConcurrentSkipListSet<E>	clone() Returns a shallow copy of this ConcurrentSkipListSet instance.
Comparator<? super E>	comparator() Returns the comparator used to order the elements in this set, or null if this set uses the {@linkplain Comparable 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.
boolean	equals(Object o) Compares the specified object with this set for equality.
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.
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.
NavigableSet<E>	headSet(E toElement) Returns a view of the portion of this set whose elements are strictly less than toElement. Equivalent to headSet(toElement, false).
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.
boolean	removeAll(Collection<?> c) Removes from this set all of its elements that are contained in the specified collection.
int	size() Returns the number of elements in this set.
Spliterator<E>	spliterator() Returns a 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 from fromElement to toElement.
NavigableSet<E>	subSet(E fromElement, E toElement) Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive. Equivalent to subSet(fromElement, true, toElement, false).
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.
NavigableSet<E>	tailSet(E fromElement) Returns a view of the portion of this set whose elements are greater than or equal to fromElement. Equivalent to tailSet(fromElement, true).

Inherited Method Summary

From class java.util.AbstractSet

boolean	equals(Object o) Compares the specified object with this set for equality.
int	hashCode() Returns the hash code value for this set.
boolean	removeAll(Collection<?> c) Removes from this set all of its elements that are contained in the specified collection (optional operation).

From class java.util.AbstractCollection

boolean	add(E e) Ensures that this collection contains the specified element (optional operation). This implementation always throws an UnsupportedOperationException.
boolean	addAll(Collection<? extends E> c) Adds all of the elements in the specified collection to this collection (optional operation). This implementation iterates over the specified collection, and adds each object returned by the iterator to this collection, in turn.
void	clear() Removes all of the elements from this collection (optional operation). This implementation iterates over this collection, removing each element using the Iterator.remove operation.
boolean	contains(Object o) Returns true if this collection contains the specified element. This implementation iterates over the elements in the collection, checking each element in turn for equality with the specified element.
boolean	containsAll(Collection<?> c) Returns true if this collection contains all of the elements in the specified collection. This implementation iterates over the specified collection, checking each element returned by the iterator in turn to see if it's contained in this collection.
boolean	isEmpty() Returns true if this collection contains no elements. This implementation returns size() == 0.
abstract Iterator<E>	iterator() Returns an iterator over the elements contained in this collection.
boolean	remove(Object o) Removes a single instance of the specified element from this collection, if it is present (optional operation). This implementation iterates over the collection looking for the specified element.
boolean	removeAll(Collection<?> c) Removes all of this collection's elements that are also contained in the specified collection (optional operation). This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection.
boolean	retainAll(Collection<?> c) Retains only the elements in this collection that are contained in the specified collection (optional operation). This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection.
abstract int	size() Returns the number of elements in this collection.
<T> T[]	toArray(T[] contents) Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. This implementation returns an array containing all the elements returned by this collection's iterator in the same order, stored in consecutive elements of the array, starting with index 0.
Object[]	toArray() Returns an array containing all of the elements in this collection. This implementation returns an array containing all the elements returned by this collection's iterator, in the same order, stored in consecutive elements of the array, starting with index 0.
String	toString() Returns a string representation of this collection.

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.util.Set

abstract boolean	add(E e) Adds the specified element to this set if it is not already present (optional operation).
abstract boolean	addAll(Collection<? extends E> c) Adds all of the elements in the specified collection to this set if they're not already present (optional operation).
abstract void	clear() Removes all of the elements from this set (optional operation).
abstract boolean	contains(Object o) Returns true if this set contains the specified element.
abstract boolean	containsAll(Collection<?> c) Returns true if this set contains all of the elements of the specified collection.
abstract boolean	equals(Object o) Compares the specified object with this set for equality.
abstract int	hashCode() Returns the hash code value for this set.
abstract boolean	isEmpty() Returns true if this set contains no elements.
abstract Iterator<E>	iterator() Returns an iterator over the elements in this set.
abstract boolean	remove(Object o) Removes the specified element from this set if it is present (optional operation).
abstract boolean	removeAll(Collection<?> c) Removes from this set all of its elements that are contained in the specified collection (optional operation).
abstract boolean	retainAll(Collection<?> c) Retains only the elements in this set that are contained in the specified collection (optional operation).
abstract int	size() Returns the number of elements in this set (its cardinality).
Spliterator<E>	spliterator() Creates a Spliterator over the elements in this set.
abstract <T> T[]	toArray(T[] a) Returns an array containing all of the elements in this set; the runtime type of the returned array is that of the specified array.
abstract Object[]	toArray() Returns an array containing all of the elements in this set.

From interface java.util.Collection

abstract boolean	add(E e) Ensures that this collection contains the specified element (optional operation).
abstract boolean	addAll(Collection<? extends E> c) Adds all of the elements in the specified collection to this collection (optional operation).
abstract void	clear() Removes all of the elements from this collection (optional operation).
abstract boolean	contains(Object o) Returns true if this collection contains the specified element.
abstract boolean	containsAll(Collection<?> c) Returns true if this collection contains all of the elements in the specified collection.
abstract boolean	equals(Object o) Compares the specified object with this collection for equality.
abstract int	hashCode() Returns the hash code value for this collection.
abstract boolean	isEmpty() Returns true if this collection contains no elements.
abstract Iterator<E>	iterator() Returns an iterator over the elements in this collection.
Stream<E>	parallelStream() Returns a possibly parallel Stream with this collection as its source.
abstract boolean	remove(Object o) Removes a single instance of the specified element from this collection, if it is present (optional operation).
abstract boolean	removeAll(Collection<?> c) Removes all of this collection's elements that are also contained in the specified collection (optional operation).
boolean	removeIf(Predicate<? super E> filter) Removes all of the elements of this collection that satisfy the given predicate.
abstract boolean	retainAll(Collection<?> c) Retains only the elements in this collection that are contained in the specified collection (optional operation).
abstract int	size() Returns the number of elements in this collection.
Spliterator<E>	spliterator() Creates a Spliterator over the elements in this collection.
Stream<E>	stream() Returns a sequential Stream with this collection as its source.
abstract <T> T[]	toArray(T[] a) Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.
abstract Object[]	toArray() Returns an array containing all of the elements in this collection.

From interface java.util.NavigableSet

abstract 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.
abstract Iterator<E>	descendingIterator() Returns an iterator over the elements in this set, in descending order.
abstract NavigableSet<E>	descendingSet() Returns a reverse order view of the elements contained in this set.
abstract 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.
abstract 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.
abstract SortedSet<E>	headSet(E toElement) Returns a view of the portion of this set whose elements are strictly less than toElement. Equivalent to headSet(toElement, false).
abstract 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.
abstract Iterator<E>	iterator() Returns an iterator over the elements in this set, in ascending order.
abstract 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.
abstract E	pollFirst() Retrieves and removes the first (lowest) element, or returns null if this set is empty.
abstract E	pollLast() Retrieves and removes the last (highest) element, or returns null if this set is empty.
abstract 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.
abstract 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. Equivalent to subSet(fromElement, true, toElement, false).
abstract SortedSet<E>	tailSet(E fromElement) Returns a view of the portion of this set whose elements are greater than or equal to fromElement. Equivalent to tailSet(fromElement, true).
abstract 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.

From interface java.lang.Iterable

void	forEach(Consumer<? super T> action) Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception.
abstract Iterator<E>	iterator() Returns an iterator over elements of type T.
Spliterator<E>	spliterator() Creates a Spliterator over the elements described by this Iterable.

From interface java.util.SortedSet

abstract Comparator<? super E>	comparator() Returns the comparator used to order the elements in this set, or null if this set uses the {@linkplain Comparable natural ordering} of its elements.
abstract E	first() Returns the first (lowest) element currently in this set.
abstract SortedSet<E>	headSet(E toElement) Returns a view of the portion of this set whose elements are strictly less than toElement.
abstract E	last() Returns the last (highest) element currently in this set.
Spliterator<E>	spliterator() Creates a Spliterator over the elements in this sorted set.
abstract 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.
abstract SortedSet<E>	tailSet(E fromElement) Returns a view of the portion of this set whose elements are greater than or equal to fromElement.

Public Constructors

public ConcurrentSkipListSet ()

Constructs a new, empty set that orders its elements according to their {@linkplain Comparable natural ordering}.

public ConcurrentSkipListSet (Comparator<? super E> comparator)

Constructs a new, empty set that orders its elements according to the specified comparator.

Parameters

comparator	the comparator that will be used to order this set. If null, the {@linkplain Comparable natural ordering} of the elements will be used.

public ConcurrentSkipListSet (Collection<? extends E> c)

Constructs a new set containing the elements in the specified collection, that orders its elements according to their {@linkplain Comparable natural ordering}.

Parameters

c	The elements that will comprise the new set

Throws

ClassCastException	if the elements in c are not Comparable, or are not mutually comparable
NullPointerException	if the specified collection or any of its elements are null

public ConcurrentSkipListSet (SortedSet<E> s)

Constructs a new 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 or any of its elements are null

Public Methods

public boolean add (E 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 e.equals(e2). If this set already contains the element, the call leaves the set unchanged and returns false.

Parameters

e	element to be added to this set

Returns

• true if this set did not already contain the specified element

Throws

ClassCastException	if e cannot be compared with the elements currently in this set
NullPointerException	if the specified element is null

public 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.

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
NullPointerException	if the specified element is null

public void clear ()

Removes all of the elements from this set.

public ConcurrentSkipListSet<E> clone ()

Returns a shallow copy of this ConcurrentSkipListSet instance. (The elements themselves are not cloned.)

Returns

• a shallow copy of this set

public Comparator<? super E> comparator ()

Returns the comparator used to order the elements in this set, or null if this set uses the {@linkplain Comparable natural ordering} of its elements.

Returns

• the comparator used to order the elements in this set, or null if this set uses the natural ordering of its elements

public boolean contains (Object 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 o.equals(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 element cannot be compared with the elements currently in this set
NullPointerException	if the specified element is null

public Iterator<E> descendingIterator ()

Returns an iterator over the elements in this set in descending order.

Returns

• an iterator over the elements in this set in descending order

public NavigableSet<E> 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.

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.

Returns

• a reverse order view of this set

public boolean equals (Object o)

Compares the specified object with this set for equality. Returns true if the specified object is also a set, the two sets have the same size, and every member of the specified set is contained in this set (or equivalently, every member of this set is contained in the specified set). This definition ensures that the equals method works properly across different implementations of the set interface.

Parameters

o	the object to be compared for equality with this set

Returns

• true if the specified object is equal to this set

public E first ()

Returns the first (lowest) element currently in this set.

Returns

• the first (lowest) element currently in this set

Throws

NoSuchElementException

public 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.

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
NullPointerException	if the specified element is null

public 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. 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.

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
NullPointerException	if toElement is null
IllegalArgumentException

public NavigableSet<E> headSet (E 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).

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
NullPointerException	if toElement is null
IllegalArgumentException

public 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.

Parameters

e	the value to match

Returns

• the least element greater than e, or null if there is no such element

Throws

ClassCastException
NullPointerException	if the specified element is null

public boolean isEmpty ()

Returns true if this set contains no elements.

Returns

• true if this set contains no elements

public Iterator<E> iterator ()

Returns an iterator over the elements in this set in ascending order.

Returns

• an iterator over the elements in this set in ascending order

public E last ()

Returns the last (highest) element currently in this set.

Returns

• the last (highest) element currently in this set

Throws

NoSuchElementException

public 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.

Parameters

e	the value to match

Returns

• the greatest element less than e, or null if there is no such element

Throws

ClassCastException
NullPointerException	if the specified element is null

public E pollFirst ()

Retrieves and removes the first (lowest) element, or returns null if this set is empty.

Returns

• the first element, or null if this set is empty

public E pollLast ()

Retrieves and removes the last (highest) element, or returns null if this set is empty.

Returns

• the last element, or null if this set is empty

public boolean remove (Object o)

Removes the specified element from this set if it is present. More formally, removes an element e such that 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.)

Parameters

o	object to be removed from this set, if present

Returns

• true if this set contained the specified element

Throws

ClassCastException	if o cannot be compared with the elements currently in this set
NullPointerException	if the specified element is null

public boolean removeAll (Collection<?> c)

Removes from this set all of its elements that are contained in the specified collection. If the specified collection is also a set, this operation effectively modifies this set so that its value is the asymmetric set difference of the two sets.

Parameters

c	collection containing elements to be removed from this set

Returns

• true if this set changed as a result of the call

Throws

ClassCastException	if the class of an element of this set is incompatible with the specified collection (optional)
NullPointerException	if the specified collection or any of its elements are null

public int size ()

Returns the number of elements in this set. If this set contains more than Integer.MAX_VALUE elements, it returns Integer.MAX_VALUE.

Beware that, unlike in most collections, this method is NOT a constant-time operation. Because of the asynchronous nature of these sets, determining the current number of elements requires traversing them all to count them. Additionally, it is possible for the size to change during execution of this method, in which case the returned result will be inaccurate. Thus, this method is typically not very useful in concurrent applications.

Returns

• the number of elements in this set

public Spliterator<E> spliterator ()

Returns a Spliterator over the elements in this set.

The Spliterator reports Spliterator.CONCURRENT, Spliterator.NONNULL, Spliterator.DISTINCT, Spliterator.SORTED and Spliterator.ORDERED, with an encounter order that is ascending order. Overriding implementations should document the reporting of additional characteristic values.

The spliterator's comparator (see Spliterator.getComparator()) is null if the set's comparator (see comparator()) is null. Otherwise, the spliterator's comparator is the same as or imposes the same total ordering as the set's comparator.

Returns

• a Spliterator over the elements in this set

public 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. 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.

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
NullPointerException	if fromElement or toElement is null
IllegalArgumentException

public NavigableSet<E> subSet (E fromElement, E 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).

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
NullPointerException	if fromElement or toElement is null
IllegalArgumentException

public 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. 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.

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
NullPointerException	if fromElement is null
IllegalArgumentException

public NavigableSet<E> tailSet (E 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).

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
NullPointerException	if fromElement is null
IllegalArgumentException