Randomizing a long array with only unique digits

I'm trying to make a long array composed of the digits 0 - 9 in a random order, meaning there would be no duplicates of the same digit. I'm a novice coder, and this is what I tried to come up with.

    public static void shuffle() 
{
    long[] rn = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

    Random rand = new Random();

    for (int i = 0; i < 10; i++) {
        int n;
        n = rand.nextInt(10) + 0;

        for (int j = 0; j < 10; j++) 
        {
            if (n != rn[j]) 
            {
               j++; 
            }
            else if (n == rn[j]) 
            {

                n = rand.nextInt(10) + 0;
                if (j > 0) 
                {
                    j--;
                }
            }
        }
        rn[i] = n;
    }

    for (int l = 0; l < 10; l++) 
    {
        System.out.print(rn[l]);
    }
    System.out.println();

}

By my understanding, this shouldn't let any duplicate digits pass, yet it does. Did I do something wrong?

PS: I'm not allowed to use collections or array lists. I'm using the Ready To Program IDE which apparently doesn't support those.