Java does not print decimal places

Question

I'm trying to do a very basic operation as follows:

double a=21/5;
System.out.println(a);

However, each time I get 4.0 as the output and not 4.2. I'm encountering this for the first time. I've been using Java for years, but never came across this obscurity.

The division is an Integer division, so 21/5 = 4, then casted to Double, so 4.0. — Sotirios Delimanolis, Mar 01 '13 at 16:24
@SotiriosDelimanolis: Obviously! Damn my brain. Thanks for rescuing it. — xan, Mar 01 '13 at 16:25
@SotiriosDelimanolis: That was an *answer*, not a comment. One I'd've upvoted. :-) — T.J. Crowder, Mar 01 '13 at 16:26
@SotiriosDelimanolis: None which bothered to explain what was going on, though, you see. :-) (Even now, the edited versions of the ones there are still not nearly as good.) That's why I made the comment, nice to see *good* answers. — T.J. Crowder, Mar 01 '13 at 16:37
`int` / `int` = `int`. You are then casting the `int` result to a `double` — Steve Kuo, Mar 01 '13 at 17:01

score 10 · Answer 1 · answered Mar 01 '13 at 16:24

10

You are using integer division, which result will always be integer You should use something like this.

double a=(double)21/5;

answered Mar 01 '13 at 16:24

Arsen Alexanyan

3,061
5
25
45

score 3 · Answer 2 · answered Mar 01 '13 at 16:25

3

You are doing integer division...

Try:

double a = 21.0/5;

answered Mar 01 '13 at 16:25

RudolphEst

1,240
13
21

score 0 · Answer 3 · answered Mar 01 '13 at 16:24

0

Cast the division or specify one of the arguments as a decimal to force the return as a double:

double a = (double)21/5;

-or-

double a = 21.0/5;

answered Mar 01 '13 at 16:24

ryrich

2,164
16
24

score 0 · Answer 4 · answered Mar 01 '13 at 16:24

0

Just cast one of the numbers to double:

double a = 21/5.0;

answered Mar 01 '13 at 16:24

kamituel

34,606
6
81
98

score 0 · Answer 5 · answered Mar 01 '13 at 16:25

0

Force the cast to double. double a = 21.0/5

This is called Arithmetic promotion. This means that all terms in an equation are made equal to the variable type with the highest precision. In this case double.

answered Mar 01 '13 at 16:25

christopher

26,815
5
55
89

Java does not print decimal places

5 Answers5