Collections: LinkedHashSet keeps insertion order

LinkedHashSet de-duplicates like HashSet but preserves the order elements were first added - the usual choice for stable, unique output.

Code

var seen = new LinkedHashSet<String>();
for (String s : List.of("delta", "alpha", "delta", "charlie", "alpha")) {
    seen.add(s);
}
System.out.println("LinkedHashSet: " + seen);
System.out.println("TreeSet      : " + new TreeSet<>(seen));

Output

LinkedHashSet: [delta, alpha, charlie]
TreeSet      : [alpha, charlie, delta]

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Published 2026-07-30