Arrays3.java

import java.util.*;
import java.io.*;

public class Arrays3{
    private int[] a;
    private Random r = new Random();
    public Arrays3() {
        a=new int[20];
        for (int i=0;i<a.length;i++) {
            a[i]=r.nextInt(100);
        }
    }

    public String toString() {
        return Arrays.toString(a);
    }

    // return the index of the max element
    public int findMaxIndex() {
        if (a==null || a.length==0) 
            return -1;

               int maxi = 0;
        for (int i=0;i<a.length;i++) {
            if (a[i] > a[maxi])
                maxi = i;
        }
        return maxi;
    }

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

    public double stddev() {
        double x = 0;
        double y = 1.0/a.length;
        double m = mean();
        double ans = 0;

        for (int i=0; i<a.length; i++)
            x += (a[i] - m) * (a[i] - m);
        ans = x*y;
        return Math.sqrt(ans);
        
    }

    public int get(int n) {
        if (n>=0 && n < a.length) 
            return a[n];
        else
            return -1;
    }
    public int find(int n) {
        for (int i=0;i<a.length;i++) {
            if (a[i]==n)
                return i;
        }
        return -1;
    }

}