Added in API level 9

Summary: Methods | Inherited Methods

NavigableSet

public interface NavigableSet
implements SortedSet<E>

java.util.NavigableSet<E>

Known indirect subclasses

ConcurrentSkipListSet<E>	A scalable concurrent `NavigableSet` implementation based on a `ConcurrentSkipListMap`.
TreeSet<E>	A `NavigableSet` implementation based on a `TreeMap`.

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

From interface


        
          java.util.SortedSet

`default void`	`addFirst(E e)` Throws `UnsupportedOperationException`.
`default void`	`addLast(E e)` Throws `UnsupportedOperationException`.
`abstract 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.
`abstract 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.
`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.
`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 SortedSet<E>`	`reversed()` Returns a reverse-ordered view of this collection.
`default 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.
`static <E> Set<E>`	`copyOf(Collection<? extends E> coll)` Returns an unmodifiable Set containing the elements of the given 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.
`static <E> Set<E>`	`of(E e1, E e2, E e3)` Returns an unmodifiable set containing three elements.
`static <E> Set<E>`	`of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9)` Returns an unmodifiable set containing nine elements.
`static <E> Set<E>`	`of(E e1, E e2, E e3, E e4, E e5)` Returns an unmodifiable set containing five elements.
`static <E> Set<E>`	`of(E e1, E e2, E e3, E e4, E e5, E e6)` Returns an unmodifiable set containing six elements.
`static <E> Set<E>`	`of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8)` Returns an unmodifiable set containing eight elements.
`static <E> Set<E>`	`of(E... elements)` Returns an unmodifiable set containing an arbitrary number of elements.
`static <E> Set<E>`	`of()` Returns an unmodifiable set containing zero elements.
`static <E> Set<E>`	`of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10)` Returns an unmodifiable set containing ten elements.
`static <E> Set<E>`	`of(E e1, E e2)` Returns an unmodifiable set containing two elements.
`static <E> Set<E>`	`of(E e1, E e2, E e3, E e4, E e5, E e6, E e7)` Returns an unmodifiable set containing seven elements.
`static <E> Set<E>`	`of(E e1, E e2, E e3, E e4)` Returns an unmodifiable set containing four elements.
`static <E> Set<E>`	`of(E e1)` Returns an unmodifiable set containing one element.
`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).
`default Spliterator<E>`	`spliterator()` Creates a `Spliterator` over the elements in this set.
`abstract Object[]`	`toArray()` Returns an array containing all of 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.

From interface


        
          java.util.SequencedSet


        abstract
        
        
        
        
        SequencedSet<E>


      reversed()

Returns a reverse-ordered view of this collection.

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.
`default 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).
`default 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.
`default Spliterator<E>`	`spliterator()` Creates a `Spliterator` over the elements in this collection.
`default 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.
`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.

From interface


        
          java.util.SequencedCollection

`default void`	`addFirst(E e)` Adds an element as the first element of this collection (optional operation).
`default void`	`addLast(E e)` Adds an element as the last element of this collection (optional operation).
`default E`	`getFirst()` Gets the first element of this collection.
`default E`	`getLast()` Gets the last element of this collection.
`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).
`abstract SequencedCollection<E>`	`reversed()` Returns a reverse-ordered view of this collection.

From interface


        
          java.lang.Iterable

`default 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`.
`default Spliterator<E>`	`spliterator()` Creates a `Spliterator` over the elements described by this `Iterable`.

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