What's wrong with this division? [duplicate]

Answer 1

The first one is 0 because it is doing integer division. -1 and 9 and integers and when divided equal 0. The result is then converted into a double so it can be stored in fraction. The easiest solution is this:

fraction = -1.0/9;

Answer 2

1 and 9 are both integer. Try

1.0/9

This is why it works for fraction/9, since fraction is a double.

Answer 3

It's doing integer division in the first example as this is the default type for a numeric literal. Try changing it to -1.0/9 (or 1d/9d - the d suffix indicates a double) and you should get the same answer.

Answer 4

When you do -1/9, it says "-1, that's an int. 9, that's an int. -1 / 9 in integer division is 0. Oh, now I need to cast to double."

Changing it to -1.0 / 9 should solve the problem.

Answer 5

Try wrapping the "-1/9" in brackets.

Answer 6

Because -1 and 9 are integers, so -1/9 is an integer division (with the result 0, which when cast to double is 0.0).

To do a floating point division, you should convert one of the numbers to double, (double) 9, 9d or simply 9.0.

In the latter case, fraction is already double (-1.0) so fraction/9 is a floating point division.