Collections: SequencedSet keeps order and uniqueness

LinkedHashSet implements SequencedSet in Java 21, so it now supports addFirst, getLast and reversed() directly.

Code

SequencedSet<String> tags = new LinkedHashSet<>(List.of("java", "spring"));

tags.addFirst("featured");
tags.addLast("kafka");
tags.addFirst("java");            // moves the existing element to the front

System.out.println(tags);
System.out.println("first = " + tags.getFirst() + ", last = " + tags.getLast());
System.out.println("reversed = " + tags.reversed());

Output

[java, featured, spring, kafka]
first = java, last = kafka
reversed = [kafka, spring, featured, java]

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Published 2026-07-30