Question

My goal is to find the package (as string) of a Java source file, given as plaintext and not already sorted in folders.

I can’t just locate the first instance of the keyword package in the file, because it may appear inside a comment. So I was thinking about two alternatives:

• Scan the file word-by-word, maintaining an “inside-a-comment” flag for the scanner. The first time the package keyword is encountered while not inside a comment, stop the scanning and report the result.
• Use a regex – should be theoretically possible because block comments do not next in Java, but I tried making such a regex and it turned out to be quite complicated – for me, at least.

Another difference between the two approaches is that when scanning manually I can stop the scan when I can be certain the package keyword can no longer appear, saving some time… and I’m not sure I can do something similar with regexes. On the other hand, the decision “when it can no longer appear” is not necessarily simple, though I could use some heuristic for that.

I would like to hear any input on this problem, and would welcome any help with the regex. My solution is written in Java as well.

EDIT: to those suggesting actually parsing the file – it’s definitely a viable option, thank you, but it feels a bit of an overkill for me to parse the whole file for just the package. I’ll do it if there’s no simpler alternative.

Answer 1

I solved this problem by using a java parser. For my purpose javaparser was the best fit.

CompilationUnit cu = JavaParser.parse( file );
String packageName = cu.getPackage().getName().toString();