We monitor the general source code quality at three places:
codacy is a hosted service to monitor code quality. It thereby combines the results of available open source code quality checkers such as Checkstyle or PMD. The code quality analysis for JabRef is available at https://app.codacy.com/gh/JabRef/jabref/dashboard, especially the list of open issues. In case a rule feels wrong, it is most likely a PMD rule. The JabRef team can change the configuration at https://app.codacy.com/p/306789/patterns/list?engine=9ed24812-b6ee-4a58-9004-0ed183c45b8f.
Teamscale is a popular German product analyzing code quality. The analysis results are available at https://demo.teamscale.com/findings.html#/jabref/?.
We strongly recommend to read following two books on code quality:
Java by Comparison is a book by three JabRef developers which focuses on code improvements close to single statements. It is fast to read and one gains much information from each recommendation discussed in the book.
Effective Java is the standard book for advanced Java programming. Did you know that
enum is the recommended way to enforce a singleton instance of a class? Did you know that one should refer to objects by their interfaces?
The principles we follow to ensure high code quality in JabRef is stated at our Development Strategy.