Interface NavigableSet<E>

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 interfaceNavigableSet<E>extendsSortedSet<E>
ASortedSet extended with navigation methods reporting closest matches for given search targets. Methodslower(E),floor(E),ceiling(E), andhigher(E) return elements respectively less than, less than or equal, greater than or equal, and greater than a given element, returningnull if there is no such element.

ANavigableSet may be accessed and traversed in either ascending or descending order. ThedescendingSet() 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 methodspollFirst() andpollLast() that return and remove the lowest and highest element, if one exists, else returningnull. MethodssubSet(E, boolean, E, boolean),headSet(E, boolean), andtailSet(E, boolean) differ from the like-namedSortedSet methods in accepting additional arguments describing whether lower and upper bounds are inclusive versus exclusive. Subsets of anyNavigableSet must implement theNavigableSet interface.

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

MethodssubSet(E, E),headSet(E), andtailSet(E) are specified to returnSortedSet to allow existing implementations ofSortedSet to be compatibly retrofitted to implementNavigableSet, but extensions and implementations of this interface are encouraged to override these methods to returnNavigableSet.

This interface is a member of the Java Collections Framework.

Since:
1.6

  • Method Summary

    Modifier and Type
    Method
    Description
    Returns the least element in this set greater than or equal to the given element, ornull if there is no such 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.
    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.
    Returns an iterator over the elements in this set, in ascending order.
    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).
    defaultE
    Removes and returns the first element of this collection (optional operation).
    defaultE
    Removes and returns the last element of this collection (optional operation).
    defaultNavigableSet<E>
    Returns a reverse-orderedview of this collection.
    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 interface java.util.Collection

    parallelStream,removeIf,stream,toArray

    Methods declared in interface java.lang.Iterable

    forEach

    Methods declared in interface java.util.SortedSet

    addFirst,addLast,comparator,first,getFirst,getLast,last,spliterator

  • Method Details

    • lower

      E lower(E e)
      Returns the greatest element in this set strictly less than the given element, ornull if there is no such element.
      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 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, ornull if there is no such element.
      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 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, ornull if there is no such element.
      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 does not permit null elements

    • higher

      E higher(E e)
      Returns the least element in this set strictly greater than the given element, ornull if there is no such element.
      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 does not permit null elements

    • pollFirst

      E pollFirst()
      Retrieves and removes the first (lowest) element, or returnsnull if this set is empty (optional operation).
      Returns:
      the first element, ornull if this set is empty
      Throws:
      UnsupportedOperationException - if thepollFirst operation is not supported by this collection

    • pollLast

      E pollLast()
      Retrieves and removes the last (highest) element, or returnsnull if this set is empty (optional operation).
      Returns:
      the last element, ornull if this set is empty
      Throws:
      UnsupportedOperationException - if thepollLast 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 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.

      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 todescendingSet().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 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.

      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 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

      NavigableSet<E> 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. 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.

      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 does not permit null elements
      IllegalArgumentException - if this set itself has a restricted range, andtoElement 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, 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.

      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 does not permit null elements
      IllegalArgumentException - if this set itself has a restricted range, andfromElement 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 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 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 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

      SortedSet<E> headSet(E toElement)
      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 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 does not permit null elements
      IllegalArgumentException - if this set itself has a restricted range, andtoElement 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 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 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 does not permit null elements
      IllegalArgumentException - if this set itself has a restricted range, andfromElement 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 thepollFirst method. Otherwise, it throwsNoSuchElementException.
      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 thepollLast method. Otherwise, it throwsNoSuchElementException.
      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-orderedview 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 todescendingSet.

      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 thedescendingSet method.
      Returns:
      a reverse-ordered view of this collection, as aNavigableSet
      Since:
      21