Added in API level 1

SortedSet

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

java.util.SortedSet<E>


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.

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

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:
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