return stat(f.getAbsolutePath(), STAT_EXISTS) == 1;
return access(f.getAbsolutePath(), ACCESS_F_OK) == 0;
  public static boolean exists(File f) {    if (f.getPath().length() == 0) return false;    SecurityManager security = System.getSecurityManager();    if (security != null)      security.checkRead(f.getPath());    return stat(f.getAbsolutePath(), STAT_EXISTS) == 1;  }