Question

I would like to build a regexp in Java that would be passed in a FilenameFilter to filter the files in a dir.

The problem is that I can’t get the hang of the regexp ‘mind model’ 🙂

This is the regexp that I came up with to select the files that I would like to exclude

((ABC|XYZ))+\w*Test.xml

What I would like to do is to select all the files that end with Test.xml but do not start with ABC or XYZ.

Could you please add any resources that could help me in my battle with regexps.

Thanks

The following resource explains a lot of things about regexp regular-expressions.info

Answer 1

What I would like to do is to select all the files that end with Test.xml but do not start with ABC or XYZ.

Either you match all your files with this regex:

^(?:(?:...)(?<!ABC|XYZ).*?)?Test\.xml$ 

or you do the opposite, and take every file that does not match:

^(?:ABC|XYZ).*?Test\.xml$ 

Personally, I find the second alternative much simpler.

 ABC_foo_Test.xml   // #2 matches XYZ_foo_Test.xml   // #2 matches ABCTest.xml        // #2 matches  XYZTest.xml        // #2 matches DEF_foo_Test.xml   // #1 matches DEFTest.xml        // #1 matches Test.xml           // #1 matches