It doesn't depend on modules. And in fact, you don't even have to wait until runtime and throw an exception: plugins like https://github.com/basepom/duplicate-f

It doesn't depend on modules. And in fact, you don't even have to wait until runtime and throw an exception: plugins like https://github.com/basepom/duplicate-finder-maven-plugin/wiki https://github.com/basepom/duplicate-finder-maven-plugin/wik... can enforce this at build time, with neat features like allowing two classes with the same name as long as their contents are 100% identical, or allowing specific exceptions where you can confirm they aren't going to cause problems. We run this plugin where I work. We have no plans to modularize our build since the duplicate class protection would just be worse that this plugin.