2nd Time Java Code Calculator
So this is the second time I'm posting this question mostly because the first time I got no progress and results because apparently it wasn't a real question which sucks.
Anyways I have mean and median down in my code but I don't know how to do variance and standard deviation(So any help on what to use for that would be great). Also I need to have a an instance method to add a double to your data set. I do not know how to do that. Lastly I don't know how to make my code so that it displays the results, when i run it it just likes say build success and nothing shows up and happens.

Here is what I have so far:

     public class SetStat {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
              
    }
    public static double findAverage(int a[]) {
    double sum = .5;
    for (int num : a)
    sum += a;

    return sum / a.length;
    }

    public static double median(int a[]) {
    int[] b = new int[a.length];
    System.arraycopy(a, 0, b, 0, b.length);
    Arrays.sort(b);

    if (a.length % 2 = 0) {
    return (b[(b.length / 2) - 1] + b[b.length / 2]) / 2.0;
    } else {
    return b[b.length / 2];
    }
    }

2nd Time Java Code Calculator
===

So this is the second time I'm posting this question mostly because the first time I got no progress and results because apparently it wasn't a real question which sucks.
Anyways I have mean and median down in my code but I don't know how to do variance and standard deviation(So any help on what to use for that would be great). Also I need to have a an instance method to add a double to your data set. I do not know how to do that. Lastly I don't know how to make my code so that it displays the results, when i run it it just likes say build success and nothing shows up and happens.

Here is what I have so far:

     public class SetStat {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
              
    }
    public static double findAverage(int a[]) {
    double sum = .5;
    for (int num : a)
    sum += a;

    return sum / a.length;
    }

    public static double median(int a[]) {
    int[] b = new int[a.length];
    System.arraycopy(a, 0, b, 0, b.length);
    Arrays.sort(b);

    if (a.length % 2 = 0) {
    return (b[(b.length / 2) - 1] + b[b.length / 2]) / 2.0;
    } else {
    return b[b.length / 2];
    }
    }
