How to be sure that random numbers are unique and not duplicated?

Question

I have a simple code which generates random numbers

SecureRandom random = new SecureRandom();
...
public int getRandomNumber(int maxValue) {
    return rando         


        

Answer 1

For such a small number of possible values, a trivial implementation would be to put your 1000 integers in a list, and have a loop which, at each iteration, generates a random number between 0 and list.size(), pick the number stored at this index, and remove it from the list.