svoid test_javaTok_onReader() {
  S s = "Hello /* comment */ world. \"String\" 'c' '\\u1234' 123 [[hello\n]] [=[long]= ]=]";
  Producer<S> p = javaTok_onReader(new BufferedReader(new StringReader(s)));
  S t;
  new LS tok;
  while ((t = p.next()) != null) {
    tok.add(t);
    print(quote(t));
  }
  assertEquals(tok, javaTok(s));
  print("OK");
}