Added in API level 9

NavigableSet

public interface NavigableSet
implements SortedSet<E>

java.util.NavigableSet<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.

Summary

Public methods

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.

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.

This method is equivalent to descendingSet.

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 methods

Public methods

ceiling

Added in API level 9
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 E: the value to match

Returns
E 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

descendingIterator

Added in API level 9
public abstract Iterator<E> descendingIterator ()

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

Returns
Iterator<E> an iterator over the elements in this set, in descending order

descendingSet

Added in API level 9
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
NavigableSet<E> a reverse order view of this set

floor

Added in API level 9
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 E: the value to match

Returns
E 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

headSet

Added in API level 9
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 E: high endpoint of the returned set

inclusive boolean: true if the high endpoint is to be included in the returned view

Returns
NavigableSet<E> 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

headSet

Added in API level 9
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 E: high endpoint (exclusive) of the returned set

Returns
SortedSet<E> a view of the portion of this set whose elements are strictly less than toElement

Throws
ClassCastException
NullPointerException
IllegalArgumentException

higher

Added in API level 9
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 E: the value to match

Returns
E 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

iterator

Added in API level 9
public abstract Iterator<E> iterator ()

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

Returns
Iterator<E> an iterator over the elements in this set, in ascending order

lower

Added in API level 9
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 E: the value to match

Returns
E 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

pollFirst

Added in API level 9
public abstract E pollFirst ()

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

Returns
E the first element, or null if this set is empty

pollLast

Added in API level 9
public abstract E pollLast ()

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

Returns
E the last element, or null if this set is empty

removeFirst

Added in API level 35
public E removeFirst ()

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

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
E the removed element

Throws
NoSuchElementException
UnsupportedOperationException

removeLast

Added in API level 35
public E removeLast ()

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

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
E the removed element

Throws
NoSuchElementException
UnsupportedOperationException

reversed

Added in API level 35
public 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.

Implementation Requirements:
  • The implementation in this interface returns the result of calling the descendingSet method.
Returns
NavigableSet<E> a reverse-ordered view of this collection, as a NavigableSet

subSet

Added in API level 9
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 E: low endpoint of the returned set

fromInclusive boolean: true if the low endpoint is to be included in the returned view

toElement E: high endpoint of the returned set

toInclusive boolean: true if the high endpoint is to be included in the returned view

Returns
NavigableSet<E> 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.

subSet

Added in API level 9
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 E: low endpoint (inclusive) of the returned set

toElement E: high endpoint (exclusive) of the returned set

Returns
SortedSet<E> a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive

Throws
ClassCastException
NullPointerException
IllegalArgumentException

tailSet

Added in API level 9
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 E: low endpoint (inclusive) of the returned set

Returns
SortedSet<E> a view of the portion of this set whose elements are greater than or equal to fromElement

Throws
ClassCastException
NullPointerException
IllegalArgumentException

tailSet

Added in API level 9
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 E: low endpoint of the returned set

inclusive boolean: true if the low endpoint is to be included in the returned view

Returns
NavigableSet<E> 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