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Java / Java 21 Collection Framework features Interview questions

List the collection classes that implement SequencedCollection in Java 21?

Every implementation of List qualifies, since a list's index order is already a well-defined encounter order - that includes ArrayList, LinkedList, Vector, Stack, and CopyOnWriteArrayList.

Every implementation of Deque also qualifies, because Deque itself now extends SequencedCollection - that covers ArrayDeque, LinkedList (again, since it implements both List and Deque), ConcurrentLinkedDeque, and LinkedBlockingDeque.

Because SequencedSet and SequencedMap both extend or relate back to this same lineage, classes like LinkedHashSet, TreeSet, LinkedHashMap, and TreeMap gain sequenced behavior indirectly through their more specific interfaces.

SequencedCollection is implemented directly by:
LinkedList qualifies as a SequencedCollection because it implements:

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