Regex for files in a directory

Question

Is it possible to use a regular expression to get filenames for files matching a given pattern in a directory without having to manually loop through all the files.

Answer 1

implement FileFilter (just requires that you override the method

public boolean accept(File f)

then, every time that you'll request the list of files, jvm will compare each file against your method. Regex cannot and shouldn't be used as java is a cross platform language and that would cause implications on different systems.

Answer 2

You could use File.listFiles(FileFilter):

public static File[] listFilesMatching(File root, String regex) {
    if(!root.isDirectory()) {
        throw new IllegalArgumentException(root+" is no directory.");
    }
    final Pattern p = Pattern.compile(regex); // careful: could also throw an exception!
    return root.listFiles(new FileFilter(){
        @Override
        public boolean accept(File file) {
            return p.matcher(file.getName()).matches();
        }
    });
}

EDIT

So, to match files that look like: TXT-20100505-XXXX.trx where XXXX can be any four successive digits, do something like this:

listFilesMatching(new File("/some/path"), "XT-20100505-\\d{4}\\.trx")