How to generate OTP Number with 6 digits

Question

What is an OTP number in a login authentication system? Is there any specific algorithm for generating OTP numbers using java (android). Or is an OTP something like random n

Answer 1

Easiest way is to just use DecimalFormat with Random class.

String otp= new DecimalFormat("000000").format(new Random().nextInt(999999));
System.out.println(otp);

Sample Outputs,

002428
445307
409185
989828
794486
213934