sS combineToJavaTokPattern(S a, S b) {
  if (a == null || b == null) null;
  L<S> tok1 = javaTok(a);
  L<S> tok2 = javaTok(b);
  if (l(tok1) != l(tok2)) null;
  new L<S> out;
  for i over tok1: {
    S t = tok1.get(i);
    bool eq = eq(t, tok2.get(i));
    if (even(i) && !eq) null; // N tokens must be equal
    out.add(eq ? t : "*");
  }
  ret join(out);
}

sS combineToJavaTokPattern(LS l) {
  ret foldl_noSeed(func(S a, S b) -> S { combineToJavaTokPattern(a, b) }, l);
}