public String check(){
    if (!myFile.exists())
      throw new FileDoesNotExistException(myFile);
    long realIfMod=myFile.lastModified();
    if (realIfMod==ifModifiedSince)
      return null;
    try {
      return Loader.loadString(new FileInputStream(myFile), 512);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }