public boolean isProbablePrime (int certainty)

Returns true if this BigInteger is probably prime, false if it's definitely composite. If certainty is ≤ 0, true is returned.

Parameters:
certainty    a measure of the uncertainty that the caller is willing to tolerate: if the call returns true the probability that this BigInteger is prime exceeds (1 - 1/2 certainty). The execution time of this method is proportional to the value of this parameter.

Returns:  true if this BigInteger is probably prime, false if it's definitely composite.