java - BigInteger.pow(BigInteger)?

Question

I'm playing with numbers in Java, and want to see how big a number I can make. It is my understanding that BigInteger can hold a number of infinite size, so long as my computer has enough Memory to hold such a number, correct?

My problem is that BigInteger.pow accepts only an int, not another BigInteger, which means I can only use a number up to 2,147,483,647 as the exponent. Is it possible to use the BigInteger class as such?

BigInteger.pow(BigInteger)

Thanks.

Answer 1

You can write your own, using repeated squaring:

BigInteger pow(BigInteger base, BigInteger exponent) {
  BigInteger result = BigInteger.ONE;
  while (exponent.signum() > 0) {
    if (exponent.testBit(0)) result = result.multiply(base);
    base = base.multiply(base);
    exponent = exponent.shiftRight(1);
  }
  return result;
}

might not work for negative bases or exponents.