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NavigableSet (Java SE 26 & JDK 26)

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Hide sidebar Show sidebar Type Parameters: E - the type of elements maintained by this set All Superinterfaces: Collection<E>, Iterable<E>, SequencedCollection<E>, SequencedSet<E>, Set<E>, SortedSet<E> All Known Implementing Classes: ConcurrentSkipListSet, TreeSet

public interface NavigableSet<E> extends SortedSet<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.

This interface is a member of the Java Collections Framework.

Since: 1.6

Method Summary

All MethodsInstance MethodsAbstract MethodsDefault Methods

Modifier and Type

Method

Description

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.

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

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.

Iterator<E>

iterator()

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

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 (optional operation).

E

pollLast()

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

default E

removeFirst()

Removes and returns the first element of this collection (optional operation).

default E

removeLast()

Removes and returns the last element of this collection (optional operation).

default NavigableSet<E>

reversed()

Returns a reverse-ordered view of this collection.

NavigableSet<E>

subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)

Returns a view of the portion of this set whose elements range from fromElement to toElement.

SortedSet<E>

subSet(E fromElement, E toElement)

Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive.

SortedSet<E>

tailSet(E fromElement)

Returns a view of the portion of this set whose elements are greater than or equal to fromElement.

NavigableSet<E>

tailSet(E fromElement, boolean inclusive)

Returns a view of the portion of this set whose elements are greater than (or equal to, if inclusive is true) fromElement.

Methods declared in interface Collection
parallelStream, removeIf, stream, toArray

Modifier and Type

Method

Description

default Stream<E>

parallelStream()

Returns a possibly parallel Stream with this collection as its source.

default boolean

removeIf(Predicate<? super E> filter)

Removes all of the elements of this collection that satisfy the given predicate (optional operation).

default Stream<E>

stream()

Returns a sequential Stream with this collection as its source.

default <T> T[]

toArray(IntFunction<T[]> generator)

Returns an array containing all of the elements in this collection, using the provided generator function to allocate the returned array.

Methods declared in interface Iterable
forEach

Modifier and Type

Method

Description

default void

forEach(Consumer<? super E> action)

Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception.

Methods declared in interface Set
add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, remove, removeAll, retainAll, size, toArray, toArray

Modifier and Type

Method

Description

boolean

add(E e)

Adds the specified element to this set if it is not already present (optional operation).

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).

void

clear()

Removes all of the elements from this set (optional operation).

boolean

contains(Object o)

Returns true if this set contains the specified element.

boolean

containsAll(Collection<?> c)

Returns true if this set contains all of the elements of the specified collection.

boolean

equals(Object o)

Compares the specified object with this set for equality.

int

hashCode()

Returns the hash code value for this set.

boolean

isEmpty()

Returns true if this set contains no elements.

boolean

remove(Object o)

Removes the specified element from this set if it is present (optional operation).

boolean

removeAll(Collection<?> c)

Removes from this set all of its elements that are contained in the specified collection (optional operation).

boolean

retainAll(Collection<?> c)

Retains only the elements in this set that are contained in the specified collection (optional operation).

int

size()

Returns the number of elements in this set (its cardinality).

Object[]

toArray()

Returns an array containing all of the elements in this set.

<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.

Methods declared in interface SortedSet
addFirst, addLast, comparator, first, getFirst, getLast, last, spliterator

Modifier and Type

Method

Description

default void

addFirst(E e)

Throws UnsupportedOperationException.

default void

addLast(E e)

Throws UnsupportedOperationException.

Comparator<? super E>

comparator()

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

E

first()

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

default E

getFirst()

Gets the first element of this collection.

default E

getLast()

Gets the last element of this collection.

E

last()

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

default Spliterator<E>

spliterator()

Creates a Spliterator over the elements in this sorted set.

Method Details
- lower
  
  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
- floor
  
  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
- ceiling
  
  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
- higher
  
  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
- pollFirst
  
  E pollFirst()
  
  Retrieves and removes the first (lowest) element, or returns null if this set is empty (optional operation).
  Returns: the first element, or null if this set is empty Throws: UnsupportedOperationException - if the pollFirst operation is not supported by this collection
- pollLast
  
  E pollLast()
  
  Retrieves and removes the last (highest) element, or returns null if this set is empty (optional operation).
  Returns: the last element, or null if this set is empty Throws: UnsupportedOperationException - if the pollLast operation is not supported by this collection
- iterator
  
  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 Set<E> Returns: an iterator over the elements in this set, in ascending order
- descendingSet
  
  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
- descendingIterator
  
  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
- subSet
  
  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.
- headSet
  
  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
- tailSet
  
  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
- subSet
  
  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).
  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 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
- headSet
  
  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).
  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 than 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
- tailSet
  
  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).
  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 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
- removeFirst
  
  default E removeFirst()
  
  Removes and returns the first element of this collection (optional operation).
  Specified by: removeFirst in interface SequencedCollection<E> Specified by: removeFirst in interface SortedSet<E> Implementation Requirements: If this set is not empty, the implementation in this interface returns the result of calling the pollFirst method. Otherwise, it throws NoSuchElementException. Returns: the removed element Throws: NoSuchElementException - if this collection is empty UnsupportedOperationException - if this collection implementation does not support this operation Since: 21
- removeLast
  
  default E removeLast()
  
  Removes and returns the last element of this collection (optional operation).
  Specified by: removeLast in interface SequencedCollection<E> Specified by: removeLast in interface SortedSet<E> Implementation Requirements: If this set is not empty, the implementation in this interface returns the result of calling the pollLast method. Otherwise, it throws NoSuchElementException. Returns: the removed element Throws: NoSuchElementException - if this collection is empty UnsupportedOperationException - if this collection implementation does not support this operation Since: 21
- reversed
  
  default NavigableSet<E> reversed()
  
  Returns a reverse-ordered view of this collection. The encounter order of elements in the returned view is the inverse of the encounter order of elements in this collection. The reverse ordering affects all order-sensitive operations, including those on the view collections of the returned view. If the collection implementation permits modifications to this view, the modifications "write through" to the underlying collection. Changes to the underlying collection might or might not be visible in this reversed view, depending upon the implementation.
  This method is equivalent to descendingSet.
  Specified by: reversed in interface SequencedCollection<E> Specified by: reversed in interface SequencedSet<E> Specified by: reversed in interface SortedSet<E> Implementation Requirements: The implementation in this interface returns the result of calling the descendingSet method. Returns: a reverse-ordered view of this collection, as a NavigableSet Since: 21

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Interface NavigableSet<E>

Method Summary

Methods declared in interface Collection

Methods declared in interface Iterable

Methods declared in interface Set

Methods declared in interface SortedSet

Method Details

lower

floor

ceiling

higher

pollFirst

pollLast

iterator

descendingSet

descendingIterator

subSet

headSet

tailSet

subSet

headSet

tailSet

removeFirst

removeLast

reversed