Question

I want to create 10 random numbers in the range 0-500. But the problem is that I want those numbers to be unique. For 2 random numbers i could create something as the following:

int randomItem1 = r.nextInt(500);
int randomItem2 = r.nextInt(500);
while(randomItem1==randomItem2){
    randomItem1=randomItem();
    randomItem2=randomItem();
}

But if I do this for 10, I think that the while it will stack. And I’m saying this because I’m trying to create a huge algorithm which is trying to make continuous evaluations and i want continously to take 10 random and unique numbers. I don’t know what to do. Any ideas or suggestions?

Answer 1

Make a LinkedList of the numbers from 1-500 and shuffle one out of them each time you use a number using The Fisher-Yates shuffle.

This will give you guaranteed sane (constant time) performance for each number pulled.