code: public static FileFilter getFileFilter() {
          return new FileFilter() {
  
              @Override
              public boolean accept(File pathname) {
                  //Accept if input  is a non-hidden file with registered extension
                  //or if a non-hidden and not-ignored directory
                  return !pathname.isHidden() && (pathname.isFile()
                      && Engines.getRecognizedExtensions().contains(fileExt(pathname))) || (directoryOnlyIfNotIgnored(pathname));
              }
          };
      }
docs: Filters files based on their file extension.
  
  @return Object for filtering files