Code:
/**
** Java Program to Implement SolovayStrassen Primality Test Algorithm
**/
import java.util.Scanner;
import java.util.Random;
/** Class SolovayStrassen **/
public class SolovayStrassen
{
/** Function to calculate jacobi (a/b) **/
public long Jacobi(long a, long b)
{
if (b <= 0 || b % 2 == 0)
return 0;
long j = 1L;
if (a < 0)
{
a = -a;
if (b % 4 == 3)
j = -j;
}
while (a != 0)
{
while (a % 2 == 0)
{
a /= 2;
if (b % 8 == 3 || b % 8 == 5)
j = -j;
}
long temp = a;
a = b;
b = temp;
if (a % 4 == 3 && b % 4 == 3)
j = -j;
a %= b;
}
if (b == 1)
return j;
return 0;
}
/** Function to check if prime or not **/
public boolean isPrime(long n, int iteration)
{
/** base case **/
if (n == 0 || n == 1)
return false;
/** base case - 2 is prime **/
if (n == 2)
return true;
/** an even number other than 2 is composite **/
if (n % 2 == 0)
return false;
Random rand = new Random();
for (int i = 0; i < iteration; i++)
{
long r = Math.abs(rand.nextLong());
long a = r % (n - 1) + 1;
long jacobian = (n + Jacobi(a, n)) % n;
long mod = modPow(a, (n - 1)/2, n);
if(jacobian == 0 || mod != jacobian)
return false;
}
return true;
}
/** Function to calculate (a ^ b) % c **/
public long modPow(long a, long b, long c)
{
long res = 1;
for (int i = 0; i < b; i++)
{
res *= a;
res %= c;
}
return res % c;
}
/** Main function **/
public static void main (String[] args)
{
Scanner scan = new Scanner(System.in);
System.out.println("SolovayStrassen Primality Algorithm Test\n");
/** Make an object of SolovayStrassen class **/
SolovayStrassen ss = new SolovayStrassen();
/** Accept number **/
System.out.println("Enter number\n");
long num = scan.nextLong();
/** Accept number of iterations **/
System.out.println("\nEnter number of iterations");
int k = scan.nextInt();
/** check if prime **/
boolean prime = ss.isPrime(num, k);
if (prime)
System.out.println("\n"+ num +" is prime");
else
System.out.println("\n"+ num +" is composite");
}
}
Output:
SolovayStrassen Primality Algorithm Test
Enter number
9997777
Enter number of iterations
1
9997777 is prime
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