Developers · Updated 18 Oct, 08:17 pm IST

Java 17 adds sealed classes to enable exhaustive pattern matching

Why it matters for readers: It shows how Java is adopting ideas from functional languages to make pattern matching more precise.

Sealed classes let an interface or base class explicitly list its permitted subtypes.1
Using sealed classes with switch expressions enables compiler exhaustiveness checking so a default clause is not required if all cases are handled.1
The article demonstrates sealed interfaces combined with record types and a switch expression example that returns values for each case.1
The feature is compared to algebraic datatype declarations in functional languages like Haskell and ML.1

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