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Claude bc91b9c8d0 Add patterns module: pattern matching from JDK 21 to 27

Type, record and primitive patterns, guards, sealed exhaustiveness, MatchException via separate compilation, and eight captured transcripts.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01TF9JWFvJSNm6HVzswzZU5a

2026-09-24 11:50:40 +00:00

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patterns — Pattern matching from JDK 21 to 27

Companion code for the ankurm.com article Pattern Matching in Java: switch, Record Patterns and Primitive Patterns (JDK 21 to 27). The explanation lives in the article; this folder holds the runnable sources and the transcripts they produced.

JDK25=/path/to/jdk-25 JDK27=/path/to/jdk-27 [JDK21=/path/to/jdk-21] ./run.sh    # regenerates output/*.txt

src/ compiles and runs on 21, 25 and 27 (except Unnamed.java, which needs 22 or later).
broken/ fails to compile on purpose.
preview/ uses primitive patterns (JEP 532, preview in 27) and needs --enable-preview --release N.
sep/ is a sealed hierarchy compiled in two versions, to show the one runtime failure an exhaustive switch cannot prevent.

Tested on Temurin 25.0.4.1+1 and 27+35, and OpenJDK 21.0.10 for the baseline.

865 B Raw Permalink Blame History

patterns — Pattern matching from JDK 21 to 27

865 B

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