Question

All,

I have implemented a code that generates 2 random prime numbers and the multiplication of these 2 numbers should pass the Miller Rabin primality test. However, my code keeps looping all the time trying to find a number that passes Miller rabin test and ends up with a Stackoverflow exception. Here is the code:

private void populateRandomPrimes()
{
    onePrimeValue = RandomPrime.getValue();

    do
    {
        secondPrimeValue= RandomPrime.getValue();
    }while(onePrimeValue == secondPrimeValue);

    BigInteger calcNum = new BigInteger(Integer.toString(onePrimeValue*secondPrimeValue));

    try
    {
        **if (calcNum.isProbablePrime(20))**
            populateMultiplicativeForPlayer();
        else
            populateRandomPrimes();
    }
    catch (Exception io)
    {
        io.printStackTrace();
    }
}

In the code above:
1 > RandomPrime class returns a random prime number
2 > Both onePrimeValue and secondPrimeValue should be different
3 > Since the code line : if (calcNum.isProbablePrime(20)) never returns a true, I end up calling the same till I get Stackoverflow exception

Can anyone suggest me how to get around with this issue?

Answer 1

Please see my comment below your question…

private void populateRandomPrimes()
{
    while (true){
      onePrimeValue = RandomPrime.getValue();

      do
      {
          secondPrimeValue= RandomPrime.getValue();
      }while(onePrimeValue == secondPrimeValue);

      BigInteger calcNum = new BigInteger(Integer.toString(onePrimeValue*secondPrimeValue));

      try
      {
          if (calcNum.isProbablePrime(20)){
              populateMultiplicativeForPlayer();
              return;
          }
      }
      catch (Exception io)
      {
          io.printStackTrace();
      }
    }
}