CasLubbers The Boy Scout Rule in Java
Leave the code cleaner than you found it. Not rewritten — cleaner. Small, safe, obviously-correct improvements made in passing keep a codebase from decaying, without turning every ticket into a refactor.
The bargain
While making the change you were asked for, fix what is in front of you. Do not go looking.
In scope — the method you are editing, the ones it calls, the file you are already in. Out of scope — the rest of the package, unrelated files, anything needing its own test plan.
Safe cleanups
Each of these is verifiable by the existing test suite and reviewable in seconds:
| Cleanup | Skill |
|---|---|
| Rename a cryptic variable or method | java-clean-names |
| Delete a redundant or stale comment | java-clean-comments |
| Delete commented-out code | java-clean-comments |
| Extract a named method from a long one | java-clean-functions |
| Replace a magic number with a constant | java-clean-general |
| Replace nesting with a guard clause | java-clean-functions |
Return Optional or an empty list instead of null |
java-clean-functions |
Add final to a field that never changes |
java-clean-general |
Replace an instanceof chain with a sealed switch |
java-clean-general |
| Add the missing boundary test you noticed | java-clean-tests |
Add @Disabled reason text |
java-clean-tests |
| Delete a genuinely unused private method | java-clean-functions |
Stop here
Leave these for their own change, and mention them instead of doing them:
- Changing behaviour, or anything a test does not cover
- Restructuring a class hierarchy or moving code between packages
- Changing a public API or method signature others call
- Upgrading a dependency or a framework annotation style
- Reformatting a whole file — it buries the real change in the diff
Keep the diff readable
The reviewer must be able to see the actual change. If the cleanup is bigger than the fix, split it into a second commit: fix: reject zero-amount transfers, then refactor: extract validateAmount. Two small commits review faster than one mixed one.
Never mix a cleanup with a behaviour change in the same commit. When something breaks, the bisect must land on one or the other.
When you find something too big
Say it, do not silently absorb it:
Fixed the rounding bug.
PaymentProcessoralso builds its ownHttpClientin three places and can't be tested without a network — worth a follow-up, too big for this change.
Run the tests
A cleanup that breaks a test was not a cleanup. Run the suite before and after; if a rename touched a reflection-based framework binding, the compiler will not catch it.