Robin Miller Primality Test

RobinMillerPrimalityTest.java

import java.math.BigInteger;
import java.util.Random;
import java.util.Scanner;

public class RobinMillerPrimalityTest {
    private static final BigInteger ONE = new BigInteger("1");
    private static final BigInteger TWO = new BigInteger("2");

    public static void main(String[] args) {

        // Initialize the scanner class for user input
        Scanner scanner = new Scanner(System.in);

        // take the input from the user
        System.out.println("Enter the odd number : ");
        BigInteger odd = new BigInteger(String.valueOf(scanner.nextInt()));
        System.out.println("Enter the security parameter: ");
        int securityParameter = scanner.nextInt();

        // exponent and odd number
        BigInteger oddMinusOne = odd.subtract(ONE);
        BigInteger oddMinusTwo = odd.subtract(TWO);
        int exponentU = oddMinusOne.getLowestSetBit();

        BigInteger oddNumberR = odd.divide(TWO.pow(exponentU));

        for (int i = 1; i < securityParameter; i++) {
            // Pick a random number a such that {2, ...., oddMinusTwo}
            Random rand = new Random();
            BigInteger randomA;
            do{
                randomA = new BigInteger(odd.bitLength(), rand);
            }while (randomA.compareTo(oddMinusOne) >= 0 || randomA.compareTo(TWO) == -1);

            BigInteger resultPowModulo = randomA.modPow(oddMinusOne, odd);

            if (!resultPowModulo.equals(ONE)){
                System.out.println("p(tilda) is composite!");
                System.exit(0);
            }

            for (int j = 1; j < exponentU; j++) {
                // BigInteger resultModuloDouble = randomA.modPow(oddNumberR.multiply(new BigInteger(String.valueOf(doubleJ))))
                if (randomA.modPow(TWO.pow(j).multiply(oddNumberR), odd).equals(ONE) && randomA.modPow(TWO.pow(j).subtract(ONE).multiply(oddNumberR), odd) != ONE){
                    System.out.println("p(tilda) is composite");
                    System.exit(0);
                }
            }
        }
        System.out.println("p(tilda) is likely a prime");
    }
}