JDK 25 refresh: declare the Java version, build it, and prove it

[watson-ki7mt]

No source file is touched. The examples compile unchanged on JDK 25 — written against Java 8 in 2017, clean today with zero errors. What had rotted was everything around them.

What was actually wrong

The README told readers to install Java 8 Update 151 — October 2017. For a repo aimed at students that's the line that matters, because a beginner installs exactly what the README says. That was the whole security story here: no third-party dependencies, no network or file I/O, no deserialization, nothing for a CVE to attach to. Just an instruction to install an eight-year-old JDK.

There was no build file, so the Java version was whatever JDK happened to be installed.

39 of 53 files are CRLF from the original Windows authoring, with no .gitattributes declaring intent — whole-file diffs for anyone on Linux or macOS.

What this adds

pom.xml + two module poms	Java version declared once; a future release is a one-line change, not 47 edits
.github/workflows/build.yml	Linux, Windows, macOS — on push, PR, and monthly
.gitattributes	line endings, going forward
README	JDK 25 LTS, plus command-line build and run instructions

Sources stay in src/ rather than moving to src/main/java — the layout is part of what the examples teach, and moving 38 files would bury the change.

The monthly cron matters more than it looks: it's what makes the next incompatibility show up as a red build rather than a discovery in 2034.

Verified, not assumed

mvn clean compile          # JDK 25.0.4.1, exit 0, 43 classes (27 console + 16 GUI)
javac --release 25         # exit 0, 10 lint warnings, no errors

And the commands the README now documents were run as written:

java -cp ConsoleApps/target/classes beam.example.radio.station.RadioStationDriver
  Station Call ....: KI7MT
  Operator ........: Greg Beam, KI7MT

Left alone deliberately

• The code, including style, Javadoc headers and Allman braces.
• 10 lint warnings — [serial] and [this-escape] in the two Swing frames. Cosmetic, and this-escape is arguably a teaching point rather than a defect. Happy to address separately if wanted.
• Existing line endings — .gitattributes fixes intent without rewriting every line of blame. A git add --renormalize . would clean them in one commit if you'd rather.
• Eclipse/IntelliJ project files — still work; .idea/workspace.xml is per-user state that could come out of version control separately.

🤖 Generated with Claude Code

[watson-ki7mt]

Took option A, plus the two cleanups. Three commits now, each one reviewable on its own.

fe572ac — the refresh: Maven, CI, README, .gitattributes. No source touched.

0e227d1 — line endings, content-free and provable. 39 files were CRLF from the 2017 Windows authoring. git diff -w across the change is empty and every file has equal insertion/deletion counts. Also untracks .idea/workspace.xml (one person's window layout and local paths); misc.xml, modules.xml, uiDesigner.xml and vcs.xml stay, since those are shared project config.

Doing this piecemeal wasn't an option: with text=auto in place, any file anyone edits normalises on commit, so the choice was once-and-done or a permanently half-converted repo. I hit it immediately — the first warning fix came out as a 31 KB whole-file diff, which is why the ordering is renormalise first, then edit.

e7ca239 — warnings, 7 lines across the two Swing frames:

Fix	Removes	Why it's honest, not a silencer
final on FireFighterCostGUI, ButtonFrame	[this-escape]	Constructors call setLayout/setResizable before a subclass would finish initialising. Nothing extends either, and neither is meant to be — they're the app's own windows
transient on 5 fields	[serial]	JFrame is Serializable, so subclasses inherit the contract regardless of intent. These hold non-serializable working state that was never part of a persisted form

10 warnings → 3. The remaining three are [dangling-doc-comments], in files whose Javadoc header sits above the imports rather than against the class. That's the repository's comment style and it's deliberate, so they stay — three explained warnings teach a student more than ten unexplained ones.

Verified after every commit: javac --release 25 -Xlint:all exit 0, mvn clean compile 43 classes, and the examples still run.