How to make a random number 4 characters long - Java

I need to generate a random number between 0 and 9999 and then I need to make the numbers all four characters long - so if 1238 is generated its fine, but if 96 is generated it needs to display 0096, or 3 will be 0003

Here is my code so far...

public static void main(String[] args) {
    Random randomGenerator = new Random();

    for (int i = 0; i < 5; i = i++) {
        int randomInteger = randomGenerator.nextInt(9999);
        System.out.println(randomInteger);
    }

}

}