Under some conditions, javac could have modified jar or zip files places on the classpath, by writing classfile(s) to them.

The specific conditions are:
- no output directory specified (i.e. no `-d` option)
- no `-sourcepath` specified
- the jar or zip file on the classpath contains source file(s), which are compiled implicitly

This is no longer the case. Classfiles will never be written to jar or zip files, and those that would be written into the jar or zip file will be placed to the current working directory. This mimics the JDK 8 behavior.