Java double number problem

Question

why when i do 15.7 * 3
the output is 47.0999999999944
but in regular calculator it is 47.1?

Answer 1

Floating point numbers, including doubles, are just inaccurate when stored in computers.

Answer 2

I'm guessing it's because the regular calculator did round the number, the double type is more precise on the fractals I suppose, hence the lengthy digits.