File find in Java

The other day I wanted to search a directory and get a list of files that match a pattern. Basically the find command. I was very annoyed that Java didn't have anything like this built into the File API. So this little method does the trick. You might use it like

  findFiles(new File("/home/blambi/workspace"),
            File.separator,
            ".*\\.class");

to find all the class files in /home/blambi/workspace.

/**
 * Recursively searches a directory for filenames matching pattern and 
 * uses delim as the file seperator.
 * @param dir dir to search
 * @param delim file seperator
 * @param pattern string to match against
 * @return a list of strings that are the filenames that match pattern
 */
List<String> findFiles(File dir, String delim, String pattern)
{
 List<String> ls = new ArrayList<String>();
 String[] dirs = dir.list();
 for (String x:dirs)
 {
  File tmp = new File(dir,x);
  if (tmp.isDirectory())
  {
   List<String> fs = findFiles(tmp,delim,pattern);
   for (String y:fs)
   {
    ls.add(x + delim + y);
   }
  }
  else if (x.matches(pattern))
  {
   ls.add(x);
  }
 }
 return ls;
}