Code:
/**
** Java Program to Implement Fermat Primality Test Algorithm
**/
import java.util.Scanner;
import java.util.Random;
/** Class FermatPrimality **/
public class FermatPrimality
{
/** 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;
if (modPow(a, n - 1, n) != 1)
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("Fermat Primality Algorithm Test\n");
/** Make an object of FermatPrimality class **/
FermatPrimality fp = new FermatPrimality();
/** 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 = fp.isPrime(num, k);
if (prime)
System.out.println("\n"+ num +" is prime");
else
System.out.println("\n"+ num +" is composite");
}
}
Output:
Fermat Primality Algorithm Test
Enter number
999983
Enter number of iterations
2
999983 is prime
More Java Programs:
