Wrong output from an double operation

Question

I'm a beginner in Java programming. When I coded a simple console app it gave an output which was not what I wanted. My code is:

class myClass{
    public static void main(String[] args) {
        int ballsPlayed = 100;

        double o = (double)(( ballsPlayed / 6 )  + ( ( ballsPlayed % 6) / 10 ));
        System.out.println(o);
    }
}

( ( ballsPlayed % 6) / 10) should be 0.4 since remainder of 100/6 is 4 and 4/10 must give 0.4. Then the variable 'o' must give 16.4(16+0.4). But I am getting 16.0 as an output from console. What is the mistake I committed?

What do you mean by "it gave an output which was not wanted"? Was there an error, was the answer different than you were expecting? — Kmeixner
– Kmeixner, Commented May 1, 2015 at 14:08
A double isn't required to have a decimal point when instantiated :) You can declare double ballsPlayed = 100; — CubeJockey
– CubeJockey, Commented May 1, 2015 at 14:14

Md. Nasir Uddin Bhuiyan · Accepted Answer · 2015-05-01 14:18:27Z

1

You must Typecast the ballsPlayed to double because ballsPlayed is an integer. It returns the integer part of (ballsPlayed % 6) / 10. Thus you got 0 except 0.4.

Try this,

double o = (double)(( ballsPlayed / 6 )  + ((double) ( ballsPlayed % 6) / 10 ));

Here you will get 16 + 0.4 = 16.4

edited May 1, 2015 at 14:18

answered May 1, 2015 at 14:07

Md. Nasir Uddin Bhuiyan

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Comments

techPackets · Accepted Answer · 2015-05-01 14:12:21Z

1

Just change the ballsPlayed variable from int to

double ballsPlayed = 100;

this will obviate the need for multiple casts. The output of (( ballsPlayed % 6) / 10 )) will be 0 not 0.4 because the compiler is dealing with an int value.

answered May 1, 2015 at 14:12

techPackets

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Masudul · Accepted Answer · 2015-05-01 14:09:35Z

0

The output of (( ballsPlayed % 6) / 10 )) is 0 not 0.4 because all values in here is int. You need one double value for / operation to get double output. To get desired output change like

 ( (double)( ballsPlayed % 6) / 10 ))

or

(( ballsPlayed % 6) / 10.0 )) // Make 10 as double

answered May 1, 2015 at 14:09

Masudul

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DaveH · Accepted Answer · 2015-05-01 14:16:20Z

0

Your problem starts here ballsPlayed / 6

An integer divided by an integer gives an integer - casting it to double is too late, you'll just get a double representation if the truncated result from the first integer division

If you want to get a fractional result from this, you need to cast ( or declare ) one of the numbers involved in the calculation in to a floating point data type.

This is pretty much what every one else has said ....

answered May 1, 2015 at 14:16

DaveH

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Syam S · Accepted Answer · 2015-05-01 14:18:00Z

0

ballsPlayed is int so by default ballsPlayed/6 will give you int only so that is 16. Similar is the case with ballsPlayed % 6 which will give int and again division by 10 will give int which will result in 0.

Here you want the first division to be int and second division to be treated as double.. So just put the casting for second operation as

double o = (( ballsPlayed / 6 )  + ( ( (double)ballsPlayed % 6) / 10 ));

here the ballsPlayed % 6 will be 4 and (double)ballsPlayed % 6) will be 4.0, a double. You can also do the casting after division

double o = (( ballsPlayed / 6 )  + ( (double)( ballsPlayed % 6) / 10 ));

answered May 1, 2015 at 14:18

Syam S

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