public static BigInteger probablePrime(int bitLength, Random rnd)

import java.math.*;
import java.util.Random;
import java.util.Scanner;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        Scanner sc = new Scanner(System.in);
  
        // create a BigInteger object
        BigInteger biginteger;
  
        // create a integer value for bitLength
        int length = 4;
  
        // create a random object
        Random random = new Random();
  
        // call probablePrime method to find next probable prime
        // whose bit length is equal to bitLength provided as parameter.
        biginteger = BigInteger.probablePrime(length, random);
  
        String result = "ProbablePrime whose bit length is "
                        + length + " = " + biginteger;
  
        // print result value
        System.out.println(result);
    }
}

ProbablePrime whose bit length is 4 = 13