// TODO: line comments inside of /* */ comments (super-special case)
static LS getJavaLineComments(S s) {
  LS tok = javaTok(s);
  new LS out;
  for (int i = 0; i < l(tok); i += 2)
    out.addAll(regexpFirstGroups("//(.*?)[\r\n]", tok.get(i)));
  ret out;
}