Java Comparator.comparing not comparing?

Question

Following this question about sorting a list by another list, I tried to do the same thing - but from some reason it doesn\'t work for me. What am I missing?

Answer 1

You are sorting the numbers by their position in the order list, but none of the numbers occur in the order list. In this case, indexOf will return -1 for everything, meaning everything is equal to everything else. In such a case, the resulting sort order is unspecified - though you may realistically assume that it would not change.