Friday, August 11, 2017

How to write clean Java

I cannot tell you how to write good Java, but I can help you write clean Java. As usual, automation is key. It's all about the tooling.

The best thing about good tooling is that they work together: each covers a different area, does not impeded another tool, and fixing one complaint a tool reveals often fixes complaints from other tools.

This advice applies to any programming language, not just Java. Java, having the most mature ecosystem, is instructive.

The tools

Use good source control
Git is your best choice. Use either trunk-based development with feature toggles (feature flags), or gitflow patterns, depending on your needs and organization. Require full builds and testing before pushing to a shared repository; hooks can help together with your build tool.
Use good build automation
Maven or Gradle are your best choices; either is excellent. Teach the tool to be strict and fail builds if anything is not just right. Treat your build configuration as code, part of the same repository and held to the same hygiene standards. Keep your local build fast.
Use a good editor
IntelliJ is the best choice. Use inspections, intentions, and reformatting obsessively: code diffs should only show real changes, not whitespace or formatting. Use plugins to ease integrating IntelliJ with other tooling.
Keep your style consistent
Checkstyle is your best choice; other choices are needed for non-Java JVM languages. Fail your build if checkstyle complains. Keep your IntelliJ formatting and Checkstyle rules consistent. Generally, choose either Sun or Google coding standards, and be leary of deviating from them; if unsure, pick Sun.
Fully test your code
JaCoCo works well. Fail your build if coverage drops below a threshhold; rachet up the threshhold as coverage improves. Start low and aim for a 95%+ threshhold. Follow the Test Pyramid; save your end-to-end tests for CI, or run locally only once before pushing commits.
Be zealous in looking for problems
FindBugs, PMD, or Error Prone are your best choices (pick one); other choices may work better for non-Java JVM languages. Fail your build if your choice complains. Be judicious in disabling complaints (for example, FindBugs "experimental" checks, should likely be disabled).
Use code generation
Lombok is your first choice. Add others as needed (or build domain-specific code generators). Generated code does not need test coverage, style checks, or bug detection if the generator is clean and well-tested: trust it.


Dan Wallach reminded me of Error Prone, added above.

Cygwin terminal in IntelliJ

IntelliJ sports an excellent terminal emulator (the "Terminal" tab at bottom of the editor). By default it brings up a terminal native to your Operating System: CMD.EXE on Windows, $SHELL on Linux and Mac.

However I prefer Cygwin when I work on Windows. WSL is incredible, but there are still interoperability issues between its filesystem and Windows-native programs, and IntelliJ (which relies on java.exe, a Windows-native program) is still working on it.

So, how to open a Cygwin terminal in IntelliJ? Setting the program to start in Settings|Tools|Terminal|Shell path, the most obvious thing to do, does not quite work:


This is a non-interactive shell, and does not source your profile. The next try is:

C:\cygwin64\bin\bash.exe --login -i

This produces an error from IntelliJ that it cannot start the program correctly. A little checking says the leading command needs to be quoted, else IntelliJ treats the entire line as the name of the command, not as a command followed by flags. OK:

"C:\cygwin64\bin\bash.exe" --login -i

Hey, I have a shell! Unfortunately, it starts in my home directory, not in my project root. Starting in the project root is one of the nice features of the terminal in IntelliJ. Finally, two changes. First the IntelliJ setting:

"C:\cygwin64\bin\bash" -c "exec /usr/bin/env INTELLIJ=true $SHELL --login -i"

And an addition to my ~/.bashrc:

${INTELLIJ-false} && cd ${OLDPWD-.}

Ipso presto!