SequencedSet (Java SE 25 & JDK 25)
Description: declaration: module: java.base, package: java.util, interface: SequencedSet
Keywords: java.util.SequencedSet interface

# Interface SequencedSet<E>

Type Parameters:
  `E` - the type of elements in this sequenced set

All Superinterfaces:
  `Collection<E>, Iterable<E>, SequencedCollection<E>, Set<E>`

All Known Subinterfaces:
  `NavigableSet<E>, SortedSet<E>`

All Known Implementing Classes:
  `ConcurrentSkipListSet, LinkedHashSet, TreeSet`

public interface SequencedSet<E> extends SequencedCollection<E>, Set<E>
A collection that is both a `SequencedCollection` and a `Set`. As such, it can be thought of either as a `Set` that also has a well-defined encounter order, or as a `SequencedCollection` that also has unique elements.

This interface has the same requirements on the `equals` and `hashCode` methods as defined by `Set.equals` and `Set.hashCode`. Thus, a `Set` and a `SequencedSet` will compare equals if and only if they have equal elements, irrespective of ordering.

`SequencedSet` defines the `reversed()` method, which provides a reverse-ordered view of this set. The only difference from the `SequencedCollection.reversed` method is that the return type of `SequencedSet.reversed` is `SequencedSet`.

This class is a member of the Java Collections Framework.

Since:
  21

- ## Method Summary

  Modifier and Type
  Method
  Description
  `SequencedSet<E>`
  `reversed()`
  Returns a reverse-ordered view of this collection.

  ### Methods declared in interface Collection

  `parallelStream, removeIf, stream, toArray`

  ### Methods declared in interface Iterable

  `forEach`

  ### Methods declared in interface SequencedCollection

  `addFirst, addLast, getFirst, getLast, removeFirst, removeLast`

  ### Methods declared in interface Set

  `add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, spliterator, toArray, toArray`

- ## Method Details

  - ### reversed

    SequencedSet<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.
    Specified by:
      `reversed` in interface `SequencedCollection<E>`
    Returns:
      a reverse-ordered view of this collection, as a `SequencedSet`