java - In Maven, Why Run 'mvn clean'?

Question

I am wondering what the major difference between running mvn compile and mvn clean compile are, in practicality.

I understand what the actual difference is, that mvn clean compile deletes all the generated files and starts again from scratch, but why would we want to do this? I can assume mvn compile will regenerate files if it's necessary, right?

One thing I noticed in my project was that if you had deleted a source file, without running clean, the compiled file remains, which usually wouldn't be a problem, but could be I suppose.

Answer 1

For example: If you rename a class, the previous compiled version will remain in target/classes until you run clean. This maybe completely harmless, but it could cause issues if it is autodetected by classpath scanning and the like.