How to support unique no generator with both sequential increment and random number generator option in java using redis

I have a requirement where we need to support generation of unique number with both sequential and random increment option with or within range of numbers. Currently we support only sequential using redis so that we don’t need to handle multi-threading and multiple instances. Can someone please give some insight on how to support random number generator with/within range in redis as well? Any specific fast performing algorithm to support both case in java?

Thanks Ray