How do you produce a double in Java

Question

I have the following code where the value of d is 0.0. 

For this code block:

int num = 5;
int denom = 7;
double d = num / denom;

I want to force cast this:

double d = ((double) num) / denom;

Can someone tell me is this the correct way?

Answer 1

double num = 5;

When you do this, it avoids the casting. For more information, you can check the casting conventions here: https://docs.oracle.com/javase/specs/jls/se7/html/index.html

According to convention 5.2:

Widening primitive conversions do not lose information about the overall magnitude of a numeric value.

[...]

Conversion of an int or a long value to float, or of a long value to double, may result in loss of precision-that is, the result may lose some of the least significant bits of the value. In this case, the resulting floating-point value will be a correctly rounded version of the integer value, using IEEE 754 round-to-nearest mode (§4.2.4).

Thus you can express 5 exactly as a double.