explicit conversion integer float System.out in Java

Question

Hey guys I'm a new Java learner. I have a problem with this code: I dont see why it prints only the value of a, and not of ((9/5)*a+32) for example if a = 50 , ((9/5)*a+32) = 82 but when I compile this it prints a=50 and ((9/5)*a+32)=82.

    Scanner tt = new Scanner(System.in);
            a = tt.nextInt();
            System.out.println(a + " degrees °C match  " + ((9/5)*a+32) + "°F");

Can someone explain this to me?!

is there any relation between your title and description of question ? — Suresh Atta, Jul 01 '14 at 12:52
I would love if the compiler would flag `9/5` at least as a warning, was there is hardly a reason where you want this to become 1. — Fabian, Jul 01 '14 at 12:53

score 1 · Answer 1 · edited Jul 01 '14 at 13:37

1

9/5 is being done using integer maths. In integer, 9/5 is 1.

Try:

(9*a)/5+32

or:

(int)((9.0/5)*a+32)

edited Jul 01 '14 at 13:37

Vito Gentile

13,336
9
61
96

answered Jul 01 '14 at 12:49

Tim B

40,716
16
83
128

3

That should be a comment – Denys Séguret Jul 01 '14 at 12:50
2

@dystroy No it shouldn't. It's an answer to the question. – Tim B Jul 01 '14 at 12:51
It is now that the question completely changed ^^ – Denys Séguret Jul 01 '14 at 12:51

score 0 · Answer 2 · answered Jul 01 '14 at 12:51

0

try using

 1.80 * a + 32

or

 9 / 5.0 * a + 32

what happens in your code is that you are dividing an integer by integer and

integer / integer = integer

it leads to precision loss..so you have to convert it to float or double type.

answered Jul 01 '14 at 12:51

rock321987

10,942
1
30
43

score 0 · Answer 3 · answered Jul 01 '14 at 12:52

0

You are performing integer division, I believe you wanted

System.out.println(a + " degrees °C match  "
    + ((((double) 9) / 5) * a + 32) + "°F");

answered Jul 01 '14 at 12:52

Elliott Frisch

198,278
20
158
249

explicit conversion integer float System.out in Java

3 Answers3