# 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.

```bash
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.