Enums on steroids - let's look at sealed classes!
summary
Claim: sealed classes plus records and pattern matching replace enums to model mutually exclusive outcomes. Implementation uses Java 17+ features: a sealed Response interface with three permitted records Approval, Refusal, Suspension and a pattern‑matching switch. Built a loan evaluator returning three concrete types (three surprising benefits: no instanceof casts, no default branch, and simpler tests). Pattern matching is still a preview feature so Maven/Gradle flags are required to compile, but the example compiles and runs and removes the previous response class smell.
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chapters (13)
- 0:00Introduction
- 1:51Problem with enums
- 3:15First solution attempt
- 5:41Code smell in response class
- 7:29Introducing class hierarchy
- 8:54Using records for immutable data
- 9:35Pattern matching in Java
- 10:38Preview feature disclaimer
- 11:22Improved loan application
- 12:06Sealed classes introduction
- 13:54Final solution with sealed classes
- 15:41Testing improvements
- 16:04GitHub repository and Q&A
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