Division in Java always results in zero (0)?

Question

The function below gets two values from sharedpreferences, weight and height, and I use these to calculate the BMI, When I print the content of the values I get the values i have entered in the sharedprefs ( which is good) but then when i run a division operation on them, I always get 0 as a result.. Where is the error?

public int computeBMI(){
    SharedPreferences customSharedPreference = getSharedPreferences(
            "myCustomSharedPrefs", Activity.MODE_PRIVATE);

    String Height = customSharedPreference.getString("heightpref", "");
    String Weight = customSharedPreference.getString("weightpref", "");

    int weight = Integer.parseInt(Weight);
    int height = Integer.parseInt(Height);
    Toast.makeText(CalculationsActivity.this, Height+" "+ Weight , Toast.LENGTH_LONG).show();

    int bmi = weight/(height*height);
    return bmi;

}

You're doing integer division. Multiply by 1.0 to make it floating point. — Paul Tomblin, May 04 '12 at 20:27

score 55 · Accepted Answer · answered May 04 '12 at 20:27

55

You're doing integer division.

You need to cast one operand to double.

answered May 04 '12 at 20:27

SLaks

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score 23 · Answer 2 · edited May 23 '17 at 12:34

23

You are doing an integer division, cast the values to float and change the datatype of the variable bmi to float.

Like this:

float bmi = (float)weight/(float)(height*height);

You should also change the return type of your method public int computeBMI() to float.

I recommend you to read this stackoverflow question.

Here you have a list of the Primitive Data Types in Java with its full description.

Hope it helps!

edited May 23 '17 at 12:34

Community

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answered May 04 '12 at 20:28

Cacho Santa

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why float and not double? – Ungeheuer Jun 10 '15 at 02:48
depends on your needs and what kind of precision you need when storing that value @JohnnyCoder – Cacho Santa Jun 10 '15 at 16:48
but float might be enough for some cases – Cacho Santa Jun 10 '15 at 16:48

score 2 · Answer 3 · answered May 04 '12 at 20:30

2

Because bmi is an integer. Either declare bmi or Weight, Height as floating point numbers. When you use integers in a division, you will get integer division. When you use doubles/floats, you will get floating point division

answered May 04 '12 at 20:30

Piyush Mattoo

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Division in Java always results in zero (0)?

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