Returns a BigInteger whose value is <code>(this<sup>exponent</sup>)</code>.
Note that {@code exponent} is an integer rather than a BigInteger.
@param exponent exponent to which this BigInteger is to be raised.
@return <code>this<sup>exponent</sup></code>
@throws ArithmeticException {@code exponent} is negative. (This would
cause the operation to yield a non-integer value.)
Returns a BigInteger whose value is <code>(this<sup>exponent</sup>)</code>. Note that {@code exponent} is an integer rather than a BigInteger.
@param exponent exponent to which this BigInteger is to be raised. @return <code>this<sup>exponent</sup></code> @throws ArithmeticException {@code exponent} is negative. (This would cause the operation to yield a non-integer value.)