What is pmd?

PMD is a tool that automatically reviews your source code and flags common mistakes before they cause problems. Think of it as a spell-checker for programmers: it scans your codebase and points out issues like variables that were declared but never used, empty error-handling blocks that silently swallow failures, or places where the code creates objects unnecessarily and slows things down. It also ships with a companion feature called CPD, which finds duplicated code, so if you copied and pasted the same 50 lines into multiple files, CPD will catch it and help you clean it up. The tool works across a wide range of languages. For static analysis, it supports Java, JavaScript, Scala, PLSQL, XML, and a few others including Salesforce-specific languages like Apex and Visualforce. The copy-paste detector covers an even broader list, C, C++, C#, Python, Ruby, Go, Swift, PHP, Kotlin, and more. You run it against your code, it reads through the source files, applies a set of rules, and produces a report of what it found. This is most useful for teams that want to keep their codebase clean and maintainable without relying solely on manual code reviews. A team lead might run it as part of their build process so that every time someone submits new code, the tool automatically checks for sloppy patterns. A developer working alone could use it to catch habits they didn't realize they had. For Salesforce developers in particular, it's one of the few open-source tools that specifically supports Apex and Visualforce. The project is built in Java and is designed to be extensible, you can write your own custom rules if the built-in ones don't cover your needs. There's also a separate companion project called the PMD Rule Designer, which helps you create and test those custom rules visually. The README doesn't go into detail on how to set it up or integrate it into your workflow, but the project's website has full documentation.