Setting a seed to shuffle ArrayList in Java deterministically

Question

I have a list of integers (currently using cern.colt.list.IntArrayList). I can call \"shuffle()\" and randomly shuffle them. I would like to be able to reproduce a shuffle.

Answer 1

there is an alternative method which takes a Random as source

Answer 2

This is possible by using the shuffle method that allows you to provide the backing Random instance: Collections.shuffle(List<?> list, Random rnd):

Example:

Collections.shuffle(yourList, new Random(somePredefinedSeed));

Answer 3

You can specify the Random instance with a seed value using public static void shuffle(List list, Random rnd). For the Random(long seed) constructor you can specify a seed.

From Java Docs:

Randomly permute the specified list using the specified source of randomness. All permutations occur with equal likelihood assuming that the source of randomness is fair.