public File makeAcceptable(File pathname){
  if (accept(pathname)) {
    return pathname;
  }
 else {
    return new File(pathname.getPath() + '.' + defaultExtension);
  }
}

public File makeAcceptable ( File pathname ) { if ( accept ( pathname ) ) { return pathname ; } else { return new File ( pathname . getPath ( ) + '.' + defaultExtension ) ; } }
appends the extension to the filename , in case it is missing .
