Java, returning a value from a method

Question

Im doing a simple piece of java code here, it is a method being called to convert Fahrenheit into Celsius. However when ever i run it, the output is always 0.0.

I cant get it to output the correct calculation. There is probably some silly little thing i have forgotten to do, can someone please help me?

public class ExampleQ {

    public static void main(String[] args) {

        System.out.println(Celsius(50));
    }

    public static double Celsius(double F)
    {
        return (5 / 9) * (F - 32);
    }
}

you'd be surprised, but 5/9 == 0 in Java :) 5.0/9 is not though.. — denis.solonenko, Apr 10 '13 at 06:26

score 7 · Accepted Answer · edited May 23 '17 at 11:49

7

The error is Integer division.

In Java 5 / 9 = 0

Try:

return (5.0 / 9) * (F - 32);

edited May 23 '17 at 11:49

Community

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answered Apr 10 '13 at 06:25

BobTheBuilder

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Awesome, i knew it was something small like that, i dont usually get stumped on things like that. Thanks – drcoding Apr 10 '13 at 06:30

score 5 · Answer 2 · answered Apr 10 '13 at 06:31

5

(5/9) produce an integer division with the result "0". As a result it produce 0 for whole expression. Try

return (5.0 / 9) * (F - 32);

answered Apr 10 '13 at 06:31

Imtiaz Zaman Nishith

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Nikhil Agrawal · Answer 3 · 2013-04-10T06:52:02.780

4

Here is the solution. Tested at online compiler Ideone http://ideone.com/zRyG80

Just replace return (5 / 9) * (F - 32); with return (F - 32) * 5 / 9;

Because the reason is in the order of operators execution. In your code division is performed before multiplication which is making 5/9 = 0.

class Main {
    public static void main(String[] args) throws java.lang.Exception {

        System.out.println(Celsius(50));
    }

    public static double Celsius(double F) {
        return (F - 32) * 5 / 9;
    }
}

Output

10.0

edited Apr 10 '13 at 06:52

answered Apr 10 '13 at 06:35

Nikhil Agrawal

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+1 for provinding link of an online compiler and debugging tool – Ram Dutt Shukla Apr 10 '13 at 06:46

score 3 · Answer 4 · answered Apr 10 '13 at 06:27

3

5 / 9 returns 0, since you're performing integer division.

Use 5.0 / 9.0 instead

answered Apr 10 '13 at 06:27

PM 77-1

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score 2 · Answer 5 · answered Apr 10 '13 at 06:28

2

(5/9) is interpreted as integer and rounded to 0.0.

To avoid integer you can replace it with (5.0/9).

answered Apr 10 '13 at 06:28

Matt

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score 2 · Answer 6 · answered Apr 10 '13 at 06:28

2

Or else you can use below code

return (5d / 9d) * (F - 32);

answered Apr 10 '13 at 06:28

Ankit HTech

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Java, returning a value from a method

6 Answers6