Java math isnt making sense

Question

OK so this is a problem in a larger piece of code which does'nt seem to make sense. below is the code which is the problem... It prints Ratio = 0.0 the console when launched it should be equal to ~0,348.

public class MathTest {

    public static void main(String[] args) {

        double ratio = 29511 / 84812;
        System.out.println("Ratio = "+ ratio);

    }

}

Edit:

What if the code is this:

public class MathTest {

    public static void main(String[] args) {
        int int1 = 7;
        int int2 = 13;
        double double1 = int1/int2;
        System.out.println("double1 = "+ double1);

    }

}

It again prints "0.0".

score 6 · Accepted Answer · answered May 20 '13 at 17:46

6

You have unwittingly used integer division when you say 29511 / 84812, which in Java, loses the decimal points. Use double literals (with .0 added) instead:

double ratio = 29511.0 / 84812.0;

Other solutions that work here:

Cast one of them to a double: (double) 29511 / 84812
Use 'D' as another way to indicate a Java double literal: 29511D / 84812D

answered May 20 '13 at 17:46

rgettman

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2

Or double ratio = 29511D / 84812D; – Mena May 20 '13 at 17:47
What if there are two ints such as int int1 = 7; int int2 = 13; double double1 = int1/int2; System.out.println("double1 = "+ double1); – user2313066 May 20 '13 at 17:49
@Mean Correct, that's another way. – rgettman May 20 '13 at 17:50
Thanks 6 mins till i can mark sloved :) – user2313066 May 20 '13 at 17:54

score 3 · Answer 2 · answered May 20 '13 at 17:47

3

You are doing integer division because 29511 and 84812 are ints. The result of the division is 0, and you are saving it as a double so it becomes 0.0.

To fix this, cast one of the operands on the right side of the assignment to a double.

double ratio = (double)29511 / 84812;

answered May 20 '13 at 17:47

Colin D

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Thanks this solved the second problem – user2313066 May 20 '13 at 17:53

score 0 · Answer 3 · answered May 20 '13 at 17:47

0

Replace double ratio = 29511 / 84812 with double ratio = 29511.0 / 84812.0;

answered May 20 '13 at 17:47

Adam Siemion

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score 0 · Answer 4 · answered May 20 '13 at 17:47

0

It make perfect sense. You are dividing two integers to get an integer. This means 0 in this case.

answered May 20 '13 at 17:47

Peter Lawrey

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Java math isnt making sense

4 Answers4