Intro to Java - What's wrong?

Question

First of all, I'm very new. So, I was able to get this to run when everything was int, but for some reason changing it to double, I can only input the first value and it errors. I don't understand why I can't do this:

        int datVal = Integer.parseInt(inNum);

        double [] iOne;
        iOne = new double[datVal];

There is no error until I run it or debug it. Here's what I've got:

import java.util.Arrays;

import javax.swing.JOptionPane;

public class arStats2 {
    public static void main(String[] args) {
        double med, men, min, max;
        String inNum = JOptionPane.showInputDialog("Enter the number of data values:");

        int datVal = Integer.parseInt(inNum);

        double [] iOne;
        iOne = new double[datVal];

        double [] iTwo;
        iTwo = new double[datVal];

        int index=0;

        for (index=0; index < iOne.length; index++) {

            String value = JOptionPane.showInputDialog("Input a data value:");
            int valIn = Integer.parseInt(value);
            iOne[index] = valIn;
        }

        System.arraycopy(iOne, 0, iTwo, 0, iOne.length);
        Arrays.sort(iOne);

        String out1 = "Sorted data: ";
        for (int i=0; i<iOne.length; i++) {
            out1 = out1 +iOne[i]+"";
        }
        out1 = out1 +"\n";

        String out2 = "Original data: ";
        for (int i2=0; i2<iTwo.length; i2++) {
            out2 = out2 +iTwo[i2] + "";
        }
        out2 = out2 +"\n";

        med = median(iOne);
        men = mean(iTwo);
        max = computeMax(iOne);
        min = computeMin(iOne);

        JOptionPane.showMessageDialog(null, out2 +out1 +"Min Value: " +min +"\n"
                                        +"Max value: " +max +"\n"
                                        +"Median value: " +med +"\n"
                                        +"Mean value: " +men +"\n");
        }

    public static double median(double[] iOne) {

        double med;
        int index, indexHi, indexLo;
        if ((iOne.length %2) !=0) {
            index = iOne.length / 2;
            med = iOne[index];
        }
        else {
            indexHi = iOne.length / 2;
            indexLo = indexHi = 1;
            med = (iOne[indexLo] + iOne[indexHi])/2;
        }
        return med;
    }

    public static double mean(double[] iOne) {
        double sum = 0;
        for (int i = 0; i < iOne.length; i++) {
            sum += iOne[i];
        }
        return sum / iOne.length;
    }

    public static double computeMax(double[] iOne) {
        double max = (iOne.length - 1);
        return max;
    }

    public static double computeMin(double[] iOne) {
        double min;
        min = iOne[0];
        return min;
    }
    }

The error is:

Exception in thread "main" java.lang.NumberFormatException: For input string: "7.2"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
    at java.lang.Integer.parseInt(Integer.java:456)
    at java.lang.Integer.parseInt(Integer.java:497)
    at arStats2.main(arStats2.java:25)

Might help you understand your error better if you research runtime vs compile time. http://stackoverflow.com/questions/846103/runtime-vs-compile-time — ddavison, Apr 29 '13 at 20:09
I updated the question with the error. Sorry for excluding that when posting! — Smeaux, Apr 29 '13 at 21:43

score 2 · Accepted Answer · answered Apr 29 '13 at 20:05

2

You need to parse the values as double here:

 for (index=0; index < iOne.length; index++) {

        String value = JOptionPane.showInputDialog("Input a data value:");
        double valIn = Double.parseDouble(value); // this line is changed
        iOne[index] = valIn;
    }

This will make it work with double values, but there are also other problems in your code, as pointed out by ValarDohaeris.

answered Apr 29 '13 at 20:05

NoToast

98
5
15

I tried parsing it as double before posting this. When I do that, it prompts me at the line: iOne = new double[datVal]; to change datVal to int. – Smeaux Apr 29 '13 at 20:53
I copy-pasted your code and added my modification. The output doesn't seem to be correct, but there are no warnings or errors in the code for me. – NoToast Apr 29 '13 at 20:57
So what you did looks like this: `double med, men, min, max; String inNum = JOptionPane.showInputDialog("Enter the number of data values:"); double datVal = Double.parseDouble(inNum); iOne[index] = datVal; double [] iOne; iOne = new double[datVal];` Sorry. Like I said, I'm a newb. And I've e-mailed my professor 3 times with no response. – Smeaux Apr 29 '13 at 21:37

score 0 · Answer 2 · answered Apr 29 '13 at 20:05

It would be helpful if you could be more specific about the error. However, there are two parts of the code that I believe to be wrong:

indexLo = indexHi = 1;

should be

indexLo = indexHi - 1;

And in computeMax() you should have:

double max = iOne[iOne.length - 1];

score -1 · Answer 3 · answered Apr 29 '13 at 20:09

-1

but for some reason changing it to double, I can only input the first value and it errors.

Well the reason is datVal = Integer.parseInt(inNum); expects an Integer and you are passing it a string that contains double which will result in a NumberFormatException being thrown.

you should surround this with a try{} catch {} block and do something about that.

answered Apr 29 '13 at 20:09

Nimooli

89
6

I didn't downvote! I wouldn't know whether it were right or wrong! – Smeaux Apr 29 '13 at 20:49

Intro to Java - What's wrong?

3 Answers3