Java 21 sealed types and pattern matching offer a modern alternative to Visitor pattern.

A developer article argues the Visitor pattern is outdated for designing domain-specific abstract syntax trees (ASTs). It proposes using Java 21's sealed classes and pattern matching instead. This approach models the AST as a sealed hierarchy and uses exhaustive switch expressions for operations. The method eliminates boilerplate code and allows the compiler to enforce operation completeness. It results in more concise and maintainable code compared to traditional double-dispatch.