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Java sealed classes enable exhaustive pattern matching without a default case

neilmadden.blog 3 min read Editor score 6/10

The examples show sealed interfaces limiting permitted subtypes so a switch can handle every case without a default branch. This helps Java engineers make type changes easier to catch during compilation.

What

- Java sealed classes let developers explicitly list the permitted subtypes of an interface or base class.

How

- The compiler checks whether a switch covers every subtype; adding a subtype can break consumers that omit a case.

Why it matters

- For public APIs, adding a sealed subtype may require a major version bump; separately compiled consumers can instead fail at runtime.

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