Decimal Format Issues Java

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I wrote a snippet of code and i can't get it to be formatted (decimal).

Here is my code:
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Java

import java.text.DecimalFormat;
import java.util.*;
public class Mean {
    public static void main(String [] args){
        Scanner s = new Scanner(System.in);
            double[]x = new double[10];
            int i;
            for(i = 0;i < 10; i++){
                x[i] = s.nextDouble();
            }
            double mean = mean(x, i);
            double deviation = var(x);
            System.out.println("The mean is " + mean); 
            System.out.println("The standard deviation is " + deviation);
    }
public static double sum(double[] a) {
        double sum = 0.0;
        for (int i = 0; i < a.length; i++) {
            sum += a[i];
        }
        return sum;
    } 
    public static double mean(double[]x, double i){ 
        if (x.length == 0) return Double.NaN;
        double sum = sum(x);
        return sum / x.length;
    } 
    public static double var(double[] x) {
        if (x.length == 0) return Double.NaN;
        double avg = mean(x, 10);
        double sum = 0.0;
        for (int i = 0; i < x.length; i++) {
            sum += (x[i] - avg) * (x[i] - avg);
        }
        DecimalFormat myFormatter = new DecimalFormat("#,##0.00");
        return sum / myFormatter.format((Math.sqrt(x.length - 1)));
    }
}

Posted 21-Dec-13 16:08pm

Wombooo

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Comments

Sergey Alexandrovich Kryukov 21-Dec-13 23:08pm

Not a good question.

You need to do the following:

If the behavior of your code does not match what you expected, use the debugger and fix it. If you failed to do so, describe what did you want to achieve, what's expected behavior, what is observed behavior, why do you feel it's wrong. If you have some exceptions, describe steps to reproduce, complete exception information. Comment the points in code related to exception throwing/propagation. Post all what's relevant. See also: http://www.sscce.org.

—SA

Richard MacCutchan 22-Dec-13 3:51am

The statement return sum / myFormatter.format((Math.sqrt(x.length - 1))); does not look right.

2 solutions

Solution 2

it's alright buddy, i already figured it out... ;D

Posted 22-Dec-13 22:25pm

Wombooo

Comments

Sergey Alexandrovich Kryukov 29-Dec-13 19:55pm

Posting such things as is considered as abuse. Do do it.
—SA

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Peter Leow · Accepted Answer · 2013-12-21T23:37:00

Your formula for standard deviation seems odd, you may want to check with google. However, that is not issue here.
You should only do the formatting on the return double value in the calling method not in the called method. See the changes below, I am assuming you want double with 2 decimal places, if not you can always ask google.

C#

public static void main(String [] args){
             
          // your other code
          double deviation = var(x);
          DecimalFormat df = new DecimalFormat("#.##");
          System.out.println("The standard deviation is " + df.format(deviation));
    }

    public static double var(double[] x) {
        // your other code
        double deviation = Math.sqrt(sum/(x.length - 1));
        return deviation;
        //DecimalFormat myFormatter = new DecimalFormat("#,##0.00");
        //return sum / myFormatter.format((Math.sqrt(x.length - 1)));
    }