How Java generates a 6-digit verification code randomly

Case: Send SMS Verification Code, verification code when the random 6-digit number:

The code is as follows:

Getrandnum (max) {
    randnum = min + (int) (Math.random () * ((max-min) + 1));
     randnum;
}
@Test
rand () {
    System.  out. println (+ getrandnum (1,999999));
}

After execution, the log is: random number 781457

Math.random () method generates a random number, the random number is a double between 0-1, we can multiply him by a certain number, say 100, he is a random number within 100