static L<S> replaceSublist(L<S> l, L<S> x, L<S> y) {
  if (x == null) ret l;
  
  int i = 0;
  while (true) {
    i = indexOfSubList(l, x, i);
    if (i < 0) break;
    
    // It's inefficient :D
    for (int j = 0; j < l(x); j++) l.remove(i);
    l.addAll(i, y);
    i += l(y);
  }
  ret l;
}