Powerful digit sum is a problem in which one must find the maximum digital sum considering natural numbers of the form, a^b, where a, b < 100.
Since we are dealing with big numbers, we should use BigIntegers. This library has the method pow() which makes our life easier when calculating powers of BigIntegers.
Then, it is just a matter of calculating the sum of all the digits in the BigInteger, and returning the maximum.
The full solution can be found here.