RandomNumberUtil

public class RandomNumberUtil { 

    public static String getRandomNumber(){
        String[] beforeShuffle = new String[] {"0","1","2","3","4","5","6","7","8","9"}; 
        List list = Arrays.asList(beforeShuffle); 
        Collections.shuffle(list);
        StringBuilder sb = new StringBuilder(); 
        for (int i = 0; i < list.size(); i++) { 
            sb.append(list.get(i));
        }
        String afterShuffle = sb.toString(); 
        return afterShuffle.substring(3, 9) ;
    }
    public static void main(String[] args) {
        System.out.println(getRandomNumber());
    }

}