高手进！！！

Question

package rsa;
import java.math.*;
import java.util.*;
import java.security.*;
public class Main
{
      final public static int bitLength=300;
      final public static SecureRandom rnd=new SecureRandom();
      public static void main(String[] args)
           {
                Scanner cin=new Scanner(System.in);
                BigInteger  p,q;
                q=BigInteger.probablePrime(bitLength,rnd);
                p=BigInteger.probablePrime(bitLength,rnd);
                System.out.println(p);
                System.out.println(q);
           }
}    
要求产生一个素数p 且（p-1）/2 也是素数
怎么修改啊？？急！！