CODEWITHSUNDEEP
javaandroidarrays
António Paulo
António Paulo

Reputation: 351

Java average returns me infinity

my program use a Write to save a double(ratingbar.rating) and a read to put the saved file inside a array. Then, with the array, I do an average of the numbers inside the array. In the read code, when I had getResources("raw.file") was working fine and the return was correct, but now I need to write the numbers and for that I can't use the res folder, so now I'm using the Internal Storage and my average returns me INFINITY. The average is called in a button OnClickListener. I'll post the code:

Write

private void writeMyArray(double rate){
    //PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("arraymedia.txt", true)));
    //.println(rate);
    double ratex2 = rate * 2;
    int erate = (int)ratex2;
        try{
            OutputStreamWriter outputStreamWriter = new OutputStreamWriter(openFileOutput("myarray.txt", Context.MODE_APPEND));
            outputStreamWriter.append(Integer.toString(erate));
            outputStreamWriter.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
}

Read

private void readMyArray(ArrayList<Double>array){
    String ret = "";
    try {
        InputStream inputStream = openFileInput("myarray.txt");

        if (inputStream != null) {
            InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
            String receiveString = "";
            StringBuilder stringBuilder = new StringBuilder();
            int enc = 0;
            while ((receiveString = bufferedReader.readLine()) != null) {
                stringBuilder.append(receiveString);
                array.add(enc, Double.parseDouble(receiveString));
                ++enc;
            }
            inputStream.close();
        }
    } catch (FileNotFoundException e) {
            e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Average

private double media(ArrayList<Double>array)
{
    double total = 0;
    double media;
    int a = 1;
    for (int i=0; i<array.size(); i++)
    {
        total = total + array.get(i);
        a=i;
    }
    media = total / a;
    return media;
}

Button

button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            rating = ratingbar.getRating();

           writeMyArray(rating);
            readMyArray(arraydays);
            button.setText(getText(R.string.obrigado) + "!" + media(arraydays));
            //button.setText(getText(R.string.obrigado)+"!");
            ratingbar.setEnabled(false);
            button.setEnabled(false);
        }
    });

Upvotes: 2

Views: 433

Answers (3)

Jordi Castilla
Jordi Castilla

Reputation: 26961

In your loop there is a mistake, dont use a=i, that cause (if only one element) a=0 with result of infinity. use i+1 instead to add 1 in each iteration

int i = 0;
for (i=0; i<array.size(); i++)
{
    total = total + array.get(i);
    // a=i;  // wrong
}
media = total / (i + 1);
return media;

Upvotes: 0

Danielson
Danielson

Reputation: 2696

private double media(ArrayList<Double>array){
    double total = 0;
    double media;
    int a = array.size(); // set to size of array, instead of setting to i
    for (int i=0; i<array.size(); i++) {
        total = total + array.get(i);
    }
    if(a==0) //if a == 0 // divide by 0 -> infinity
        media = 0;
    else
        media = total / a;
    return media;
}

Upvotes: 0

Raman Shrivastava
Raman Shrivastava

Reputation: 2953

Division amounts to infinity in java if your denominator is 0.0 (0 in float or double). Please check before dividing.

Upvotes: 3

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