Interpreter Pattern In Light of Java 21
summary
Classic Interpreter bakes evaluation into mutable domain objects so changing interpretation forces edits and mixing of concerns; modern Java 21 split solves that by modeling expressions as a sealed hierarchy of records (Constant, Sum, Subtract, Multiply) and writing external interpreters implemented with sealed classes, pattern matching and switch expressions to produce evaluators that return values, pretty-printed strings, or asynchronous results via CompletableFuture. Examples show a runner evaluating RPN-style expressions, an async evaluator, and notes on bringing in monadic types like Either/Option and type-class-style flatMap to move map/flatMap outside the model.
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chapters (9)
- 0:00Introduction to patterns
- 2:39The classic interpreter
- 12:17Modernizing the approach
- 19:25Sealed classes and pattern matching
- 25:40Advanced pattern matching
- 31:00Externalizing interpretations
- 37:11Functional concepts
- 43:00Scala and monadic patterns
- 53:58Future perspectives
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