static bool equalsIgnoreCase(S a, S b) {
  ret a == null ? b == null : a.equalsIgnoreCase(b);
}

static bool equalsIgnoreCase(char a, char b) {
  if (a == b) true;
  char u1 = Character.toUpperCase(a);
  char u2 = Character.toUpperCase(b);
  if (u1 == u2) true;
  ret Character.toLowerCase(u1) == Character.toLowerCase(u2);
}