Added in API level 1

Summary: Methods | Inherited Methods

SortedSet

public interface SortedSet
implements Set<E>, SequencedSet<E>

java.util.SortedSet<E>

Known indirect subclasses

ConcurrentSkipListSet<E>, NavigableSet<E>, TreeSet<E>

ConcurrentSkipListSet<E>	A scalable concurrent `NavigableSet` implementation based on a `ConcurrentSkipListMap`.
NavigableSet<E>	A `SortedSet` extended with navigation methods reporting closest matches for given search targets.
TreeSet<E>	A `NavigableSet` implementation based on a `TreeMap`.

A Set that further provides a total ordering on its elements. The elements are ordered using their ordering, or by a Comparator typically provided at sorted set creation time. The set's iterator will traverse the set in ascending element order. Several additional operations are provided to take advantage of the ordering. (This interface is the set analogue of SortedMap.)

All elements inserted into a sorted set must implement the Comparable interface (or be accepted by the specified comparator). Furthermore, all such elements must be mutually comparable: e1.compareTo(e2) (or comparator.compare(e1, e2)) must not throw a ClassCastException for any elements e1 and e2 in the sorted set. Attempts to violate this restriction will cause the offending method or constructor invocation to throw a ClassCastException.

Note that the ordering maintained by a sorted set (whether or not an explicit comparator is provided) must be consistent with equals if the sorted set is to correctly implement the Set interface. (See the Comparable interface or Comparator interface for a precise definition of consistent with equals.) This is so because the Set interface is defined in terms of the equals operation, but a sorted set performs all element comparisons using its compareTo (or compare) method, so two elements that are deemed equal by this method are, from the standpoint of the sorted set, equal. The behavior of a sorted set is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the Set interface.

All general-purpose sorted set implementation classes should provide four "standard" constructors: 1) A void (no arguments) constructor, which creates an empty sorted set sorted according to the natural ordering of its elements. 2) A constructor with a single argument of type Comparator, which creates an empty sorted set sorted according to the specified comparator. 3) A constructor with a single argument of type Collection, which creates a new sorted set with the same elements as its argument, sorted according to the natural ordering of the elements. 4) A constructor with a single argument of type SortedSet, which creates a new sorted set with the same elements and the same ordering as the input sorted set. There is no way to enforce this recommendation, as interfaces cannot contain constructors.

Note: several methods return subsets with restricted ranges. Such ranges are half-open, that is, they include their low endpoint but not their high endpoint (where applicable). If you need a closed range (which includes both endpoints), and the element type allows for calculation of the successor of a given value, merely request the subrange from lowEndpoint to successor(highEndpoint). For example, suppose that s is a sorted set of strings. The following idiom obtains a view containing all of the strings in s from low to high, inclusive:

   SortedSet<String> sub = s.subSet(low, high+"\0");

A similar technique can be used to generate an open range (which contains neither endpoint). The following idiom obtains a view containing all of the Strings in s from low to high, exclusive:

   SortedSet<String> sub = s.subSet(low+"\0", high);

This interface is a member of the Java Collections Framework.

See also:

Summary

Public methods
`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`.

Inherited methods

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

addFirst

Added in API level 35

public void addFirst (E e)

Throws UnsupportedOperationException. The encounter order induced by this set's comparison method determines the position of elements, so explicit positioning is not supported.

Implementation Requirements:

The implementation in this interface always throws UnsupportedOperationException.

Parameters
`e`	`E`: the element to be added

Throws
`UnsupportedOperationException`	always

addLast

Added in API level 35

public void addLast (E e)

Throws UnsupportedOperationException. The encounter order induced by this set's comparison method determines the position of elements, so explicit positioning is not supported.

Implementation Requirements:

The implementation in this interface always throws UnsupportedOperationException.

Parameters
`e`	`E`: the element to be added.

Throws
`UnsupportedOperationException`	always

comparator

Added in API level 1

public 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.

Returns
`Comparator<? super E>`	the comparator used to order the elements in this set, or `null` if this set uses the natural ordering of its elements

first

Added in API level 1

public abstract E first ()

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

Returns
`E`	the first (lowest) element currently in this set

Throws
`NoSuchElementException`	if this set is empty

getFirst

Added in API level 35

public E getFirst ()

Gets the first element of this collection.

Implementation Requirements:

The implementation in this interface returns the result of calling the first method.

Returns
`E`	the retrieved element

Throws
`NoSuchElementException`

getLast

Added in API level 35

public E getLast ()

Gets the last element of this collection.

Implementation Requirements:

The implementation in this interface returns the result of calling the last method.

Returns
`E`	the retrieved element

Throws
`NoSuchElementException`

headSet

Added in API level 1

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.

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`	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

last

Added in API level 1

public abstract E last ()

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

Returns
`E`	the last (highest) element currently in this set

Throws
`NoSuchElementException`	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:

The implementation in this interface calls the first method to obtain the first element, then it calls remove(element) to remove the element, and then it returns the element.

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:

The implementation in this interface calls the last method to obtain the last element, then it calls remove(element) to remove the element, and then it returns the element.

Returns
`E`	the removed element

Throws
`NoSuchElementException`
`UnsupportedOperationException`

reversed

Added in API level 35

public SortedSet<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.

Implementation Requirements:

The implementation in this interface returns a reverse-ordered SortedSet view. The reversed() method of the view returns a reference to this SortedSet. Other operations on the view are implemented via calls to public methods on this SortedSet. The exact relationship between calls on the view and calls on this SortedSet is unspecified. However, order-sensitive operations generally delegate to the appropriate method with the opposite orientation. For example, calling getFirst on the view results in a call to getLast on this SortedSet.

Returns
`SortedSet<E>`	a reverse-ordered view of this collection, as a `SortedSet`

spliterator

Added in API level 24

public Spliterator<E> spliterator ()

Creates a Spliterator over the elements in this sorted set.

The Spliterator reports Spliterator#DISTINCT, Spliterator#SORTED and Spliterator#ORDERED. Implementations should document the reporting of additional characteristic values.

The spliterator's comparator (see Spliterator.getComparator()) must be null if the sorted set's comparator (see comparator()) is null. Otherwise, the spliterator's comparator must be the same as or impose the same total ordering as the sorted set's comparator.

Implementation Requirements:

The default implementation creates a late-binding spliterator from the sorted set's Iterator. The spliterator inherits the fail-fast properties of the set's iterator. The spliterator's comparator is the same as the sorted set's comparator.
The created Spliterator additionally reports Spliterator#SIZED.

Implementation Note:

The created Spliterator additionally reports Spliterator#SUBSIZED.

Returns
`Spliterator<E>`	a `Spliterator` over the elements in this sorted set

subSet

Added in API level 1

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.

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`	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

tailSet

Added in API level 1

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.

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`	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