private static int choosePrime(Random rnd){
  return Primes.FIRST_PRIMES[rnd.nextInt(10)];
}

private static int choosePrime ( Random rnd ) { return Primes . FIRST_PRIMES [ rnd . nextInt ( 10 ) ] ; }
choose a random prime . we try to avoid the later primes , as they are known to cause too correlated data .
