Shuffle/Random comparator

Question

IS there any way to emulate the behavior of Collections.shuffle without a comparator being vulnerable to the sorting algorithm implementation for the result to be safe?

Answer 1

A bit more generic to the previous answer, when the type of element is not known:

public static  Comparator shuffle() {
    final Map uniqueIds = new IdentityHashMap<>();
    return Comparator.comparing(e -> uniqueIds.computeIfAbsent(e, k -> UUID.randomUUID()));
}

can be used in streams as well:

list.stream().sorted(Streams.shuffle()).collect(Collectors.toList())

there might be collisions somehow, so it can be extended using a HashSet for the UUID to check this case