NavigableSet

public interface NavigableSet implements SortedSet<E>

Known Indirect Subclasses

ConcurrentSkipListSet<E>, TreeSet<E>

A SortedSet extended with navigation methods reporting closest matches for given search targets. Methods lower(E), floor(E), ceiling(E), and higher(E) return elements respectively less than, less than or equal, greater than or equal, and greater than a given element, returning null if there is no such element.

A NavigableSet may be accessed and traversed in either ascending or descending order. The descendingSet() method returns a view of the set with the senses of all relational and directional methods inverted. The performance of ascending operations and views is likely to be faster than that of descending ones. This interface additionally defines methods pollFirst() and pollLast() that return and remove the lowest and highest element, if one exists, else returning null. Methods subSet(E, boolean, E, boolean), headSet(E, boolean), and tailSet(E, boolean) differ from the like-named SortedSet methods in accepting additional arguments describing whether lower and upper bounds are inclusive versus exclusive. Subsets of any NavigableSet must implement the NavigableSet interface.

The return values of navigation methods may be ambiguous in implementations that permit null elements. However, even in this case the result can be disambiguated by checking contains(null). To avoid such issues, implementations of this interface are encouraged to not permit insertion of null elements. (Note that sorted sets of Comparable elements intrinsically do not permit null.)

Methods subSet(E, E), headSet(E), and tailSet(E) are specified to return SortedSet to allow existing implementations of SortedSet to be compatibly retrofitted to implement NavigableSet, but extensions and implementations of this interface are encouraged to override these methods to return NavigableSet.

Public Method Summary

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`.

Inherited Method Summary

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`.

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.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`.

Public Methods

public 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.

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	if the specified element cannot be compared with the elements currently in the set
NullPointerException	if the specified element is null and this set does not permit null elements

public abstract Iterator<E> descendingIterator ()

Returns an iterator over the elements in this set, in descending order. Equivalent in effect to descendingSet().iterator().

Returns

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

public abstract 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. 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(comparator()). The expression s.descendingSet().descendingSet() returns a view of s essentially equivalent to s.

Returns

a reverse order view of this set

public 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.

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	if the specified element cannot be compared with the elements currently in the set
NullPointerException	if the specified element is null and this set does not permit null elements

public 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. 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	if `toElement` is not compatible with this set's comparator (or, if the set has no comparator, if `toElement` does not implement `Comparable`). Implementations may, but are not required to, throw this exception if `toElement` cannot be compared to elements currently in the set.
NullPointerException	if `toElement` is null and this set does not permit null elements
IllegalArgumentException	if this set itself has a restricted range, and `toElement` lies outside the bounds of the range

public abstract SortedSet<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
IllegalArgumentException

public 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.

Parameters

e	the value to match

Returns

the least element greater than e, or null 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 does not permit null elements

public abstract 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 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.

Parameters

e	the value to match

Returns

the greatest element less than e, or null 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 does not permit null elements

public abstract 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 abstract 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 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. 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	if `fromElement` and `toElement` cannot be compared to one another using this set's comparator (or, if the set has no comparator, using natural ordering). Implementations may, but are not required to, throw this exception if `fromElement` or `toElement` cannot be compared to elements currently in the set.
NullPointerException	if `fromElement` or `toElement` is null and this set does not permit null elements
IllegalArgumentException	if `fromElement` is greater than `toElement`; or if this set itself has a restricted range, and `fromElement` or `toElement` lies outside the bounds of the range.

public 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. (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
IllegalArgumentException

public abstract SortedSet<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
IllegalArgumentException

public 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. 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	if `fromElement` is not compatible with this set's comparator (or, if the set has no comparator, if `fromElement` does not implement `Comparable`). Implementations may, but are not required to, throw this exception if `fromElement` cannot be compared to elements currently in the set.
NullPointerException	if `fromElement` is null and this set does not permit null elements
IllegalArgumentException	if this set itself has a restricted range, and `fromElement` lies outside the bounds of the range