Bug in random numbers in Android

Question

TreeSet myNumbers = new TreeSet();
Random randGen = new Random();

for (int i = 1; i <= 16; i++) {
    // number generation here
    int randNum = randGen.nextInt(16          


        

Answer 1

To generate a random number in a range, it is like:

int min = ...
int max = ...
int randNumber = min + new Random().nextInt(max - min + 1);

So in your example where you want to generate a random number from [1, 16], it would look like:

int randNumber = 1 + new Random().nextInt(16 - 1 + 1);

Or if you choose to simplify:

int randNumber = 1 + new Random().nextInt(16);

Also, you should really be using a while loop instead of an infinite for loop:

    final TreeSet myNumbers = new TreeSet<>();
    final Random rand = new Random();
    for(int i = 0; i < 16; i++){
        int n = 1 + rand.nextInt(16);
        while(!myNumbers.add(n))
            n = 1 + rand.nextInt(16);
    }