Question

Possible Duplicate:
Java Integer Division, How do you produce a double?

double wang = 3 / 2;
Log.v("TEST", "Wang: " + Double.toString(wang));

Logcat output…

07-04 09:01:03.908: VERBOSE/TEST(28432): Wang: 1.0

I’m sure there’s an obvious answer to this and probably I’m just tired from coding all night but this has me stumped.

Answer 1

In many languages, Java being one of them, the way you write a number in an expression decides what type it gets. In Java, a few of the common number types behave like this¹:

// In these cases the specs are obviously redundant, since all values will be
// cast correctly anyway, but it was the easiest way to show how to get to the
// different data types :P
int i = 1;
long l = 1L;
float f = 1.0f;   // I believe the f and d for float and double are optional, but
double d = 1.0d;  // I wouldn't bet on what the default is if they're omitted...

Thus, when you declare 3 / 2, you’re really saying (the integer 3) / (the integer 2). Java performs the division, and finds the result to be 1 (i.e. the integer 1…) since that’s the result of dividing 3 and 2 as integers. Finally, the integer 1 is cast to the double 1.0d which is stored in your variable.

To work around this, you should (as many others have suggested) instead calculate the quotient of

(the double 3) / (the double 2)

or, in Java syntax,

double wang = 3.0 / 2.0;

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¹ Source: The Java Tutorial from Oracle