Java Docs

Java Documentation (Javadoc) Best Practices

Principles

• Document only what the code actually does: read the implementation, callers and tests first. Never invent behaviour, thresholds, thread-safety, nullability or exceptions you have not verified; if unsure, leave it out or ask.

• Keep the existing documentation style of the project (language, tag order, comment form /** */ vs ///). Do not rewrite existing comments, or mass-document a codebase, unless the user asks; limit changes to the requested scope.

• Check the JDK level (maven.compiler.release, toolchain, java -version) before using newer features, and stay within it.

Conventions

• @since only with the real version in which the API was introduced; @deprecated with a reason and replacement, together with @Deprecated.

• @author and @version only if the project already uses them.

• Code blocks, by JDK level:

  • Any JDK: <pre>{@code ... }</pre> (escape @ at line start, balance braces).

  • JDK 18+: {@snippet : ... } for inline code, or {@snippet file="Example.java" region="demo"} with files in snippet-files/ (preferred for examples; javadoc does not compile or validate the snippet source, so compile and test the files in a separate build/test source set if you need that guarantee). Use // @highlight substring="x" and // @replace markup as needed.

  • JDK 23+ only (JEP 467): Markdown doc comments with ///, using [Type#member] for links and fenced code blocks. Use them only if the project already does or the user asks, and the build runs a JDK 23+ javadoc.

Verify

• Run mvn -q javadoc:javadoc (or ./gradlew javadoc) and for single files javadoc -Xdoclint:all -d target/javadoc-check <files>; fix every warning/error you introduced (missing @param, bad HTML, unresolved {@link}, unknown tags).

• Report what was documented and the commands run; state any claims you could not verify from the code.