Immutable list creation

Code Comparison

List<String> list =
    Collections.unmodifiableList(
        new ArrayList<>(
            Arrays.asList("a", "b", "c")
        )
    );

List<String> list =
    List.of("a", "b", "c");

Why the modern way wins

📏

One call

Replace three nested calls with a single factory method.

🔒

Truly immutable

Not just a wrapper — the list itself is immutable.

🛡️

Null-safe

Rejects null elements at creation time, failing fast.

Old Approach

Verbose Wrapping

Modern Approach

List.of()

JDK Support

Immutable list creation

Available

Widely available since JDK 9 (Sept 2017)

How it works

List.of() creates a truly immutable list — no wrapping, no defensive copy. It's null-hostile (rejects null elements) and structurally immutable. The old way required three nested calls.