Java sealed classes and exhaustive pattern matching

Java 17's sealed classes enable exhaustive pattern matching by restricting which types can implement an interface or extend a class, allowing the compiler to verify that all possible cases are handled in switch expressions without requiring a default clause. However, adding new subtypes to a sealed class becomes a breaking change that can cause compile-time errors for consumers, and if consumers aren't recompiled, a runtime MatchException may occur. This trade-off between safety and flexibility is an important consideration for APIs that export sealed types.