How do I make the data values to be in three decimal places?

Question

This app is almost over, but I need the output data values to be in three decimal places for the output file. So far, the final output is the one I need (square rooted of the data values from the asset file). Here is the code that I wrote for the app:

public void srAndSave(View view)
{
    EditText edt1;
    EditText edt2;
    TextView tv;

    String infilename; 
    String outfilename;

    tv = (TextView) findViewById(R.id.text_status);

    //Get the name of the input file and output file
    edt1 = (EditText) findViewById(R.id.edit_infile);
    edt2 = (EditText) findViewById(R.id.edit_outfile);

    infilename = edt1.getText().toString();
    outfilename = edt2.getText().toString();

    //Create an array that stores double values (up to 20)
    double double_nums[] = new double[20];
    int n = 0;//For storing the number of data values in the array


    //Open the data file from the asset directory
    //and make sure the data file exists
    AssetManager assetManager = getAssets();

    try
    {
        Scanner fsc = new Scanner(assetManager.open(infilename));

        //Get the data values from the file
        //and store them in the array double_nums
        n = 0;
        while(fsc.hasNext()){
            double_nums[n] = fsc.nextDouble();
            n++;
        }

        //Calls on square_root_it method
        square_root_it(double_nums, n);

        //Display that the file has been opened
        tv.setText("Opening the input file and reading the file were "
                + " successful.");

        fsc.close();

    }
    catch(IOException e)
    {
        tv.setText("Error: File " + infilename + " does not exist");

    }

    //Write the data to the output file and
    //also make sure that the existence of the file
    File outfile = new File(getExternalFilesDir(null), outfilename);
    try
    {
        FileWriter fw = new FileWriter(outfile); 

        BufferedWriter bw = new BufferedWriter(fw);

        PrintWriter pw = new PrintWriter(bw); 

        int x;

        for(x=0;x < n;x++)
            pw.println(double_nums[x]); //Write the data values that are stored in
                                        //the array, double_nums after the method call
                                        //for square_root_it

        pw.close();
    }
    catch(IOException e)
    {
        System.out.println("Error! Output file does already exist! You will overwrite"
                + " this file!");
    }

} //end srAndSave

public static void square_root_it(double[] a, int num_items)
{
    int i;

    for(i=0; i < num_items; i++)
        a[i] = Math.sqrt(a[i]); //Initialize the array a[i] to have the square root of
                                //the double values stored in double_nums[] array, and
                                //then return a[i]


} //end square_root_it

possible duplicate of [How to round a number to n decimal places in Java](http://stackoverflow.com/questions/153724/how-to-round-a-number-to-n-decimal-places-in-java) — Tim, Feb 16 '15 at 00:18

score 0 · Accepted Answer · answered Feb 16 '15 at 00:13

0

You can format a double, specifying the number of decimal places as follows:

    double d = 1.234567;
    DecimalFormat df = new DecimalFormat("#.###");
    System.out.print(df.format(d));

answered Feb 16 '15 at 00:13

BrentM

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How do I make the data values to be in three decimal places?

1 Answers1