How to calculate the median of an array?

I’m trying to calculate the total, mean and median of an array thats populated by input received by a textfield. I’ve managed to work out the total and the mean, I just can’t get the median to work. I think the array needs to be sorted before I can do this, but I’m not sure how to do this. Is this the problem, or is there another one that I didn’t find? Here is my code:

import java.applet.Applet;
import java.awt.Graphics;
import java.awt.*;
import java.awt.event.*;

public class whileloopq extends Applet implements ActionListener
{
    Label label;
    TextField input;
    int num;
    int index;
    int[] numArray = new int[20];
    int sum;
    int total;
    double avg;
    int median;



    public void init ()
    {
        label = new Label("Enter numbers");
        input = new TextField(5);
        add(label);
        add(input);
        input.addActionListener(this);
        index = 0;
    }

    public void actionPerformed (ActionEvent ev)
    {
        int num = Integer.parseInt(input.getText());
        numArray[index] = num;
        index++;
        if (index == 20)
        input.setEnabled(false);
            input.setText("");
        sum = 0;
        for (int i = 0; i < numArray.length; i++)
        {
            sum += numArray[i];
        }
        total = sum;
        avg = total / index;

        median = numArray[numArray.length/2];



        repaint();

    }



    public void paint (Graphics graf)
    {



        graf.drawString("Total   = " + Integer.toString(total), 25, 85);
        graf.drawString("Average = " + Double.toString(avg), 25, 100);
        graf.drawString("Median = " + Integer.toString(median), 25, 115);



    }
}

Answer

The Arrays class in Java has a static sort function, which you can invoke with Arrays.sort(numArray).

Arrays.sort(numArray);
double median;
if (numArray.length % 2 == 0)
    median = ((double)numArray[numArray.length/2] + (double)numArray[numArray.length/2 - 1])/2;
else
    median = (double) numArray[numArray.length/2];

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Answer