Help for developing JOpt Simple

This page has notes and hints for contributing to JOpt Simple, mostly around getting started and style questions.

Code Style

Style is important. Why? Chiefly to aid merges. Reformatting code makes merging more difficult. When needing to reformat unchanged code, please do so on a separate commit with a clear commit message indicating a non-code change.

In general use the Eclipse formatter (there is a plugin for IntelliJ IDEA). See jopt-simple-eclipse-formatting.xml and jopt-simple.importorder in the project root.

The ultimate arbiter of good style is Paul Holser.


  • Yes:
    for (int i = 0; i < 10; ++i) {
        if (i < 5)
  • No:
    for (int i = 0; i < 10; ++i)
        if (i < 5)


There are no integration tests. Your typical command line is:

$ mvn clean test

Before pushing commits, please check that the site fully builds:

$ mvn clean post-site