Faster Random Number Generator

I am a really really new noobie high school student in java and we're currently optimizing a project but I'm stuck now. I think one of the problems is about picking random numbers between 1 and 4. I'm currently using splittable

// a was instantiated   
int i = a.nextInt(1, 5);

but I still can't speed my code up to the benchmark. is there any other way that's faster? (I searched about xoroshiro but don't know how to use it. can anyone provide an example of how to do it from importing and something like that?)

thanks a lot.