Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary: [Methods](https://developer.android.com/reference/java/util/NavigableSet#pubmethods) \| [Inherited Methods](https://developer.android.com/reference/java/util/NavigableSet#inhmethods)

# NavigableSet


`
public


interface
NavigableSet
`


`


implements

https://developer.android.com/reference/java/util/SortedSet<E>


`

|---|
| java.util.NavigableSet\<E\> |

|---|
| Known indirect subclasses [ConcurrentSkipListSet](https://developer.android.com/reference/java/util/concurrent/ConcurrentSkipListSet)\<E\>, [TreeSet](https://developer.android.com/reference/java/util/TreeSet)\<E\> |---|---| | [ConcurrentSkipListSet](https://developer.android.com/reference/java/util/concurrent/ConcurrentSkipListSet)\<E\> | A scalable concurrent `https://developer.android.com/reference/java/util/NavigableSet` implementation based on a `https://developer.android.com/reference/java/util/concurrent/ConcurrentSkipListMap`. | | [TreeSet](https://developer.android.com/reference/java/util/TreeSet)\<E\> | A `https://developer.android.com/reference/java/util/NavigableSet` implementation based on a `https://developer.android.com/reference/java/util/TreeMap`. | |

<br />

*** ** * ** ***

A `https://developer.android.com/reference/java/util/SortedSet` extended with navigation methods reporting
closest matches for given search targets. Methods `https://developer.android.com/reference/java/util/NavigableSet#lower(E)`,
`https://developer.android.com/reference/java/util/NavigableSet#floor(E)`, `https://developer.android.com/reference/java/util/NavigableSet#ceiling(E)`, and `https://developer.android.com/reference/java/util/NavigableSet#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 `https://developer.android.com/reference/java/util/NavigableSet#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 `https://developer.android.com/reference/java/util/NavigableSet#pollFirst()` and `https://developer.android.com/reference/java/util/NavigableSet#pollLast()` that return and remove the lowest
and highest element, if one exists, else returning `null`.
Methods
`https://developer.android.com/reference/java/util/NavigableSet#subSet(E,%20boolean,%20E,%20boolean)`,
`https://developer.android.com/reference/java/util/NavigableSet#headSet(E,%20boolean)`, and
`https://developer.android.com/reference/java/util/NavigableSet#tailSet(E,%20boolean)`
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 `https://developer.android.com/reference/java/lang/Comparable` elements intrinsically do not permit `null`.)

Methods
`https://developer.android.com/reference/java/util/NavigableSet#subSet(E,%20E)`,
`https://developer.android.com/reference/java/util/NavigableSet#headSet(E)`, and
`https://developer.android.com/reference/java/util/NavigableSet#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` | ` https://developer.android.com/reference/java/util/NavigableSet#ceiling(E)(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 https://developer.android.com/reference/java/util/Iterator<E>` | ` https://developer.android.com/reference/java/util/NavigableSet#descendingIterator()() ` Returns an iterator over the elements in this set, in descending order. |
| ` abstract https://developer.android.com/reference/java/util/NavigableSet<E>` | ` https://developer.android.com/reference/java/util/NavigableSet#descendingSet()() ` Returns a reverse order view of the elements contained in this set. |
| ` abstract E` | ` https://developer.android.com/reference/java/util/NavigableSet#floor(E)(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 https://developer.android.com/reference/java/util/NavigableSet<E>` | ` https://developer.android.com/reference/java/util/NavigableSet#headSet(E,%20boolean)(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 https://developer.android.com/reference/java/util/SortedSet<E>` | ` https://developer.android.com/reference/java/util/NavigableSet#headSet(E)(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` | ` https://developer.android.com/reference/java/util/NavigableSet#higher(E)(E e) ` Returns the least element in this set strictly greater than the given element, or `null` if there is no such element. |
| ` abstract https://developer.android.com/reference/java/util/Iterator<E>` | ` https://developer.android.com/reference/java/util/NavigableSet#iterator()() ` Returns an iterator over the elements in this set, in ascending order. |
| ` abstract E` | ` https://developer.android.com/reference/java/util/NavigableSet#lower(E)(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` | ` https://developer.android.com/reference/java/util/NavigableSet#pollFirst()() ` Retrieves and removes the first (lowest) element, or returns `null` if this set is empty (optional operation). |
| ` abstract E` | ` https://developer.android.com/reference/java/util/NavigableSet#pollLast()() ` Retrieves and removes the last (highest) element, or returns `null` if this set is empty (optional operation). |
| ` default E` | ` https://developer.android.com/reference/java/util/NavigableSet#removeFirst()() ` Removes and returns the first element of this collection (optional operation). |
| ` default E` | ` https://developer.android.com/reference/java/util/NavigableSet#removeLast()() ` Removes and returns the last element of this collection (optional operation). |
| ` default https://developer.android.com/reference/java/util/NavigableSet<E>` | ` https://developer.android.com/reference/java/util/NavigableSet#reversed()() ` Returns a reverse-ordered [view](https://developer.android.com/reference/java/util/Collection#view) of this collection. This method is equivalent to `https://developer.android.com/reference/java/util/NavigableSet#descendingSet()`. |
| ` abstract https://developer.android.com/reference/java/util/NavigableSet<E>` | ` https://developer.android.com/reference/java/util/NavigableSet#subSet(E,%20boolean,%20E,%20boolean)(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 https://developer.android.com/reference/java/util/SortedSet<E>` | ` https://developer.android.com/reference/java/util/NavigableSet#subSet(E,%20E)(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 https://developer.android.com/reference/java/util/SortedSet<E>` | ` https://developer.android.com/reference/java/util/NavigableSet#tailSet(E)(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 https://developer.android.com/reference/java/util/NavigableSet<E>` | ` https://developer.android.com/reference/java/util/NavigableSet#tailSet(E,%20boolean)(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 ` https://developer.android.com/reference/java/util/SortedSet ` |---|---| | ` default void` | ` https://developer.android.com/reference/java/util/SortedSet#addFirst(E)(E e) ` Throws `UnsupportedOperationException`. | | ` default void` | ` https://developer.android.com/reference/java/util/SortedSet#addLast(E)(E e) ` Throws `UnsupportedOperationException`. | | ` abstract https://developer.android.com/reference/java/util/Comparator<? super E>` | ` https://developer.android.com/reference/java/util/SortedSet#comparator()() ` Returns the comparator used to order the elements in this set, or `null` if this set uses the [natural ordering](https://developer.android.com/reference/java/lang/Comparable) of its elements. | | ` abstract E` | ` https://developer.android.com/reference/java/util/SortedSet#first()() ` Returns the first (lowest) element currently in this set. | | ` default E` | ` https://developer.android.com/reference/java/util/SortedSet#getFirst()() ` Gets the first element of this collection. | | ` default E` | ` https://developer.android.com/reference/java/util/SortedSet#getLast()() ` Gets the last element of this collection. | | ` abstract https://developer.android.com/reference/java/util/SortedSet<E>` | ` https://developer.android.com/reference/java/util/SortedSet#headSet(E)(E toElement) ` Returns a view of the portion of this set whose elements are strictly less than `toElement`. | | ` abstract E` | ` https://developer.android.com/reference/java/util/SortedSet#last()() ` Returns the last (highest) element currently in this set. | | ` default E` | ` https://developer.android.com/reference/java/util/SortedSet#removeFirst()() ` Removes and returns the first element of this collection (optional operation). | | ` default E` | ` https://developer.android.com/reference/java/util/SortedSet#removeLast()() ` Removes and returns the last element of this collection (optional operation). | | ` default https://developer.android.com/reference/java/util/SortedSet<E>` | ` https://developer.android.com/reference/java/util/SortedSet#reversed()() ` Returns a reverse-ordered [view](https://developer.android.com/reference/java/util/Collection#view) of this collection. | | ` default https://developer.android.com/reference/java/util/Spliterator<E>` | ` https://developer.android.com/reference/java/util/SortedSet#spliterator()() ` Creates a `Spliterator` over the elements in this sorted set. | | ` abstract https://developer.android.com/reference/java/util/SortedSet<E>` | ` https://developer.android.com/reference/java/util/SortedSet#subSet(E,%20E)(E fromElement, E toElement) ` Returns a view of the portion of this set whose elements range from `fromElement`, inclusive, to `toElement`, exclusive. | | ` abstract https://developer.android.com/reference/java/util/SortedSet<E>` | ` https://developer.android.com/reference/java/util/SortedSet#tailSet(E)(E fromElement) ` Returns a view of the portion of this set whose elements are greater than or equal to `fromElement`. | ||
| From interface ` https://developer.android.com/reference/java/util/SequencedSet ` |---|---| | ` abstract https://developer.android.com/reference/java/util/SequencedSet<E>` | ` https://developer.android.com/reference/java/util/SequencedSet#reversed()() ` Returns a reverse-ordered [view](https://developer.android.com/reference/java/util/Collection#view) of this collection. | ||
| From interface ` https://developer.android.com/reference/java/util/Set ` |---|---| | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#add(E)(E e) ` Adds the specified element to this set if it is not already present (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#addAll(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/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` | ` https://developer.android.com/reference/java/util/Set#clear()() ` Removes all of the elements from this set (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#contains(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Returns `true` if this set contains the specified element. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#containsAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Returns `true` if this set contains all of the elements of the specified collection. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#copyOf(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/Collection<? extends E> coll) ` Returns an [unmodifiable Set](https://developer.android.com/reference/java/util/NavigableSet#unmodifiable) containing the elements of the given Collection. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Compares the specified object with this set for equality. | | ` abstract int` | ` https://developer.android.com/reference/java/util/Set#hashCode()() ` Returns the hash code value for this set. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#isEmpty()() ` Returns `true` if this set contains no elements. | | ` abstract https://developer.android.com/reference/java/util/Iterator<E>` | ` https://developer.android.com/reference/java/util/Set#iterator()() ` Returns an iterator over the elements in this set. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E)(E e1, E e2, E e3) ` Returns an unmodifiable set containing three elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E,%20E,%20E,%20E,%20E,%20E)(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> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E,%20E)(E e1, E e2, E e3, E e4, E e5) ` Returns an unmodifiable set containing five elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E,%20E,%20E)(E e1, E e2, E e3, E e4, E e5, E e6) ` Returns an unmodifiable set containing six elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E,%20E,%20E,%20E,%20E)(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> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E[])(E... elements) ` Returns an unmodifiable set containing an arbitrary number of elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of()() ` Returns an unmodifiable set containing zero elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E,%20E,%20E,%20E,%20E,%20E,%20E)(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> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E)(E e1, E e2) ` Returns an unmodifiable set containing two elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E,%20E,%20E,%20E)(E e1, E e2, E e3, E e4, E e5, E e6, E e7) ` Returns an unmodifiable set containing seven elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E,%20E,%20E,%20E)(E e1, E e2, E e3, E e4) ` Returns an unmodifiable set containing four elements. | | ` static <E> https://developer.android.com/reference/java/util/Set<E>` | ` https://developer.android.com/reference/java/util/Set#of(E)(E e1) ` Returns an unmodifiable set containing one element. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#remove(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Removes the specified element from this set if it is present (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#removeAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Removes from this set all of its elements that are contained in the specified collection (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Set#retainAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Retains only the elements in this set that are contained in the specified collection (optional operation). | | ` abstract int` | ` https://developer.android.com/reference/java/util/Set#size()() ` Returns the number of elements in this set (its cardinality). | | ` default https://developer.android.com/reference/java/util/Spliterator<E>` | ` https://developer.android.com/reference/java/util/Set#spliterator()() ` Creates a `Spliterator` over the elements in this set. | | ` abstract https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/util/Set#toArray()() ` Returns an array containing all of the elements in this set. | | ` abstract <T> T[]` | ` https://developer.android.com/reference/java/util/Set#toArray(T[])(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 ` https://developer.android.com/reference/java/util/SequencedCollection ` |---|---| | ` default void` | ` https://developer.android.com/reference/java/util/SequencedCollection#addFirst(E)(E e) ` Adds an element as the first element of this collection (optional operation). | | ` default void` | ` https://developer.android.com/reference/java/util/SequencedCollection#addLast(E)(E e) ` Adds an element as the last element of this collection (optional operation). | | ` default E` | ` https://developer.android.com/reference/java/util/SequencedCollection#getFirst()() ` Gets the first element of this collection. | | ` default E` | ` https://developer.android.com/reference/java/util/SequencedCollection#getLast()() ` Gets the last element of this collection. | | ` default E` | ` https://developer.android.com/reference/java/util/SequencedCollection#removeFirst()() ` Removes and returns the first element of this collection (optional operation). | | ` default E` | ` https://developer.android.com/reference/java/util/SequencedCollection#removeLast()() ` Removes and returns the last element of this collection (optional operation). | | ` abstract https://developer.android.com/reference/java/util/SequencedCollection<E>` | ` https://developer.android.com/reference/java/util/SequencedCollection#reversed()() ` Returns a reverse-ordered [view](https://developer.android.com/reference/java/util/Collection#view) of this collection. | ||
| From interface ` https://developer.android.com/reference/java/util/Collection ` |---|---| | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#add(E)(E e) ` Ensures that this collection contains the specified element (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#addAll(java.util.Collection<?%20extends%20E>)(https://developer.android.com/reference/java/util/Collection<? extends E> c) ` Adds all of the elements in the specified collection to this collection (optional operation). | | ` abstract void` | ` https://developer.android.com/reference/java/util/Collection#clear()() ` Removes all of the elements from this collection (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#contains(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Returns `true` if this collection contains the specified element. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#containsAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Returns `true` if this collection contains all of the elements in the specified collection. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Compares the specified object with this collection for equality. | | ` abstract int` | ` https://developer.android.com/reference/java/util/Collection#hashCode()() ` Returns the hash code value for this collection. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#isEmpty()() ` Returns `true` if this collection contains no elements. | | ` abstract https://developer.android.com/reference/java/util/Iterator<E>` | ` https://developer.android.com/reference/java/util/Collection#iterator()() ` Returns an iterator over the elements in this collection. | | ` default https://developer.android.com/reference/java/util/stream/Stream<E>` | ` https://developer.android.com/reference/java/util/Collection#parallelStream()() ` Returns a possibly parallel `Stream` with this collection as its source. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#remove(java.lang.Object)(https://developer.android.com/reference/java/lang/Object o) ` Removes a single instance of the specified element from this collection, if it is present (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#removeAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Removes all of this collection's elements that are also contained in the specified collection (optional operation). | | ` default boolean` | ` https://developer.android.com/reference/java/util/Collection#removeIf(java.util.function.Predicate<?%20super%20E>)(https://developer.android.com/reference/java/util/function/Predicate<? super E> filter) ` Removes all of the elements of this collection that satisfy the given predicate (optional operation). | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/Collection#retainAll(java.util.Collection<?>)(https://developer.android.com/reference/java/util/Collection<?> c) ` Retains only the elements in this collection that are contained in the specified collection (optional operation). | | ` abstract int` | ` https://developer.android.com/reference/java/util/Collection#size()() ` Returns the number of elements in this collection. | | ` default https://developer.android.com/reference/java/util/Spliterator<E>` | ` https://developer.android.com/reference/java/util/Collection#spliterator()() ` Creates a `https://developer.android.com/reference/java/util/Spliterator` over the elements in this collection. | | ` default https://developer.android.com/reference/java/util/stream/Stream<E>` | ` https://developer.android.com/reference/java/util/Collection#stream()() ` Returns a sequential `Stream` with this collection as its source. | | ` abstract <T> T[]` | ` https://developer.android.com/reference/java/util/Collection#toArray(T[])(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 https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/util/Collection#toArray()() ` Returns an array containing all of the elements in this collection. | | ` default <T> T[]` | ` https://developer.android.com/reference/java/util/Collection#toArray(java.util.function.IntFunction<T[]>)(https://developer.android.com/reference/java/util/function/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 ` https://developer.android.com/reference/java/lang/Iterable ` |---|---| | ` default void` | ` https://developer.android.com/reference/java/lang/Iterable#forEach(java.util.function.Consumer<?%20super%20T>)(https://developer.android.com/reference/java/util/function/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 https://developer.android.com/reference/java/util/Iterator<E>` | ` https://developer.android.com/reference/java/lang/Iterable#iterator()() ` Returns an iterator over elements of type `T`. | | ` default https://developer.android.com/reference/java/util/Spliterator<E>` | ` https://developer.android.com/reference/java/lang/Iterable#spliterator()() ` Creates a `https://developer.android.com/reference/java/util/Spliterator` over the elements described by this `Iterable`. | ||

## Public methods

### ceiling

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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.

<br />

| Parameters ||
|---|---|
| `e` | `E`: the value to match <br /> |

| Returns ||
|---|---|
| `E` | the least element greater than or equal to `e`, or `null` if there is no such element <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/ClassCastException` | if the specified element cannot be compared with the elements currently in the set |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null and this set does not permit null elements |

### descendingIterator

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract Iterator<E> descendingIterator ()
```

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

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/Iterator<E>` | an iterator over the elements in this set, in descending order <br /> |

### descendingSet

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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
`https://developer.android.com/reference/java/util/Collections#reverseOrder(java.util.Comparator<T>)``(comparator())`.
The expression `s.descendingSet().descendingSet()` returns a
view of `s` essentially equivalent to `s`.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/NavigableSet<E>` | a reverse order view of this set <br /> |

### floor

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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.

<br />

| Parameters ||
|---|---|
| `e` | `E`: the value to match <br /> |

| Returns ||
|---|---|
| `E` | the greatest element less than or equal to `e`, or `null` if there is no such element <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/ClassCastException` | if the specified element cannot be compared with the elements currently in the set |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null and this set does not permit null elements |

### headSet

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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.

<br />

| Parameters ||
|---|---|
| `toElement` | `E`: high endpoint of the returned set <br /> |
| `inclusive` | `boolean`: `true` if the high endpoint is to be included in the returned view <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/NavigableSet<E>` | a view of the portion of this set whose elements are less than (or equal to, if `inclusive` is true) `toElement` <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/ClassCastException` | if `toElement` is not compatible with this set's comparator (or, if the set has no comparator, if `toElement` does not implement `https://developer.android.com/reference/java/lang/Comparable`). Implementations may, but are not required to, throw this exception if `toElement` cannot be compared to elements currently in the set. |
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if this set itself has a restricted range, and `toElement` lies outside the bounds of the range |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if `toElement` is null and this set does not permit null elements |

### headSet

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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)`.

<br />

| Parameters ||
|---|---|
| `toElement` | `E`: high endpoint (exclusive) of the returned set <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/SortedSet<E>` | a view of the portion of this set whose elements are strictly less than `toElement` <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/ClassCastException` |   |
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` |   |
| `https://developer.android.com/reference/java/lang/NullPointerException` |   |

### higher

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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.

<br />

| Parameters ||
|---|---|
| `e` | `E`: the value to match <br /> |

| Returns ||
|---|---|
| `E` | the least element greater than `e`, or `null` if there is no such element <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/ClassCastException` | if the specified element cannot be compared with the elements currently in the set |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null and this set does not permit null elements |

### iterator

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract Iterator<E> iterator ()
```

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

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/Iterator<E>` | an iterator over the elements in this set, in ascending order <br /> |

### lower

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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.

<br />

| Parameters ||
|---|---|
| `e` | `E`: the value to match <br /> |

| Returns ||
|---|---|
| `E` | the greatest element less than `e`, or `null` if there is no such element <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/ClassCastException` | if the specified element cannot be compared with the elements currently in the set |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the specified element is null and this set does not permit null elements |

### pollFirst

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract E pollFirst ()
```

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

<br />

| Returns ||
|---|---|
| `E` | the first element, or `null` if this set is empty <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` | if the `pollFirst` operation is not supported by this collection |

### pollLast

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract E pollLast ()
```

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

<br />

| Returns ||
|---|---|
| `E` | the last element, or `null` if this set is empty <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` | if the `pollLast` operation is not supported by this collection |

### removeFirst

Added in [API level 35](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public E removeFirst ()
```

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

<br />

##### 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 <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` |   |
| `https://developer.android.com/reference/java/util/NoSuchElementException` |   |

### removeLast

Added in [API level 35](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public E removeLast ()
```

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

<br />

##### 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 <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` |   |
| `https://developer.android.com/reference/java/util/NoSuchElementException` |   |

### reversed

Added in [API level 35](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public NavigableSet<E> reversed ()
```

Returns a reverse-ordered [view](https://developer.android.com/reference/java/util/Collection#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 `https://developer.android.com/reference/java/util/NavigableSet#descendingSet()`.

<br />

##### Implementation Requirements:

- The implementation in this interface returns the result of calling the `descendingSet` method.

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/NavigableSet<E>` | a reverse-ordered view of this collection, as a `NavigableSet` <br /> |

### subSet

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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.

<br />

| Parameters ||
|---|---|
| `fromElement` | `E`: low endpoint of the returned set <br /> |
| `fromInclusive` | `boolean`: `true` if the low endpoint is to be included in the returned view <br /> |
| `toElement` | `E`: high endpoint of the returned set <br /> |
| `toInclusive` | `boolean`: `true` if the high endpoint is to be included in the returned view <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/NavigableSet<E>` | a view of the portion of this set whose elements range from `fromElement`, inclusive, to `toElement`, exclusive <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/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. |
| `https://developer.android.com/reference/java/lang/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. |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if `fromElement` or `toElement` is null and this set does not permit null elements |

### subSet

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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)`.

<br />

| Parameters ||
|---|---|
| `fromElement` | `E`: low endpoint (inclusive) of the returned set <br /> |
| `toElement` | `E`: high endpoint (exclusive) of the returned set <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/SortedSet<E>` | a view of the portion of this set whose elements range from `fromElement`, inclusive, to `toElement`, exclusive <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/ClassCastException` |   |
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` |   |
| `https://developer.android.com/reference/java/lang/NullPointerException` |   |

### tailSet

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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)`.

<br />

| Parameters ||
|---|---|
| `fromElement` | `E`: low endpoint (inclusive) of the returned set <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/SortedSet<E>` | a view of the portion of this set whose elements are greater than or equal to `fromElement` <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/ClassCastException` |   |
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` |   |
| `https://developer.android.com/reference/java/lang/NullPointerException` |   |

### tailSet

Added in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
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.

<br />

| Parameters ||
|---|---|
| `fromElement` | `E`: low endpoint of the returned set <br /> |
| `inclusive` | `boolean`: `true` if the low endpoint is to be included in the returned view <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/NavigableSet<E>` | a view of the portion of this set whose elements are greater than or equal to `fromElement` <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/ClassCastException` | if `fromElement` is not compatible with this set's comparator (or, if the set has no comparator, if `fromElement` does not implement `https://developer.android.com/reference/java/lang/Comparable`). Implementations may, but are not required to, throw this exception if `fromElement` cannot be compared to elements currently in the set. |
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | if this set itself has a restricted range, and `fromElement` lies outside the bounds of the range |
| `https://developer.android.com/reference/java/lang/NullPointerException` | if `fromElement` is null and this set does not permit null elements |