Check for duplicates while populating an array

Question

I have an array that I populate with 6 randomly generated numbers. First it generates a random number between 1 and 49 and then checks it against the numbers in the array. If it finds a duplicate it should generate a random number again and then perform the check once again. If there are no duplicates then the number is added to the array.

Here's the code:

public void populateArray()
{
    for(int i = 0; i < numberLine.length; i++)
    {
        randomNumber = 1 + randomGen.nextInt(49);
        for(int j = 0; j < i; j++)
        {
            if (numberLine[j] == randomNumber)
            {
                i--;
            }
            else
            {
                continue;
            }
        }
        if(i >= 0)
        {
            numberLine[i] = randomNumber;
        }
        else
        {
            continue;
        }
    }
    Arrays.sort(numberLine);
}

However, for some reason this still lets in a duplicate, though rarely (about 1 in 50 arrays), such as 6 6 16 24 34 46. But when I try to duplicate this by taking out the random number element and using a number like 30, I am unable to reproduce the result. What's going wrong?

Answer 1

It would be a lot easier with collections, for example a TreeSet which is both sorted and without duplicate

Set<Integer> set = new TreeSet<Integer>();
while (set.length() < 6) {
    set.add(randomGen.nextInt(49));
} 

Use toArray() after that if you really want to have an array.