Java: Why can't I declare integer types using scientific notation?
I can easily read 2e15 as "two quadrillion" at a glance, but for 2000000000000000 I have to count the zeroes, which takes longer and can lead to errors.
Why can't I declare an int or long using a literal such as 2e9 or 1.3e6? I understand that a negative power of 10, such as 2e-3, or a power of 10 that is less than the number of decimal places, such as 1.0003e3, would produce a floating point number, but why doesn't Java allow such declarations, and simply truncate the floating-point part and issue a mild warning in cases where the resulting value is non-integral?
Is there a technical reason why this is a bad idea, or is this all about type-safety? Wouldn't it be trivial for the compiler to simply parse a statement like
long x = 2e12 as long x = 2000000000000 //OK for long
and int y = 2.1234e3 as int y = 2123.4 //warning: loss of precision
Answer
It's because when you use the scientific notation you create a floating point number (a double in your example). And you can't assign a floating point to an integer (that would be a narrowing primitive conversion, which is not a valid assignment conversion).
So this would not work either for example:
int y = 2d; //can't convert double to int
You have a few options:
- explicitly cast the floating point to an integer:
int y = (int) 2e6; - with Java 7+ use a thousand separator:
int y = 2_000_000;