How do I evaluate this equation?

Question

I think its pretty self explanatory from the code. Obviously I'm no evaluating the same thing over and over, its just example numbers to explain my problem. I'm guessing its over/underflow but I don't know how to deal with it.

double d = (1 / (684985+157781));

System.out.println(d); // returns 0.0
System.out.println(Math.log(d)); // returns -Infinity.

Answer 1

(1 / (684985+157781)) is an integer expression, so it will come out to 0 . The zero then gets assigned to the double d , as 0.0 .

Try changing the 1 to 1.0 to force that expression to be a float, or 1.0D to force it to double.

Answer 2

另一个人通过整数除法完成：

double d = (1.0 / (684985.0+157781.0));

Answer 3

不，在Java中，如果使用整数，除法的结果将再次为整数，您必须将至少一个操作数转换为double。

double d = (1 / (double)(684985+157781));

Answer 4

Try using double d = (1.0 / (684985+157781));

Note the 1.0 part: you want to force the double evaluation.

Answer 5

That first expression is computed in integer arithmetic. To get the answer you're expecting, you need to compute it in floating-point arithmetic, thus:

double d = (1.0 / (684985.0+157781.0));