ClaseHilo

import java.util.Random;

public class Hilo extends Thread{

    private int root;
    private double inicio;
    private double fin;
    private double tiempo;
    private int indice;

    public Hilo(int i) {
        this.indice = i;
    }
    public void run() {
        Random random = new Random();
        inicio = System.currentTimeMillis();
        root = random.nextInt(1,20);
        System.out.println(SumRootN(root));

        fin = System.currentTimeMillis();
        tiempo = fin-inicio;

        System.out.println("Tiempo transcurrido con concurrencia de hilo "+indice+": "+tiempo);
    }

    public static double SumRootN(int root) {
        double result = 0;
        for (int i = 0; i < 10000000; i++) {
            result += Math.exp(Math.log(i) / root);
        }
        return result;
    }
}