Android Studio Random Number with range and no dublicates

i was working on a quizz app in android studio..

• I have 2 tables which are the solutions and questions..
• In my game activity i wanna create a random number in range of this table without dublicates..
• with this random number i update my questions and anwsers..

I try this code now to create numbers(with dublicates):

---

Random rand = new Random();

n = rand.nextInt(QuestionLibrary.mChoices.length) + 1;

---