ca;łka

public class MyThread extends Thread {

    private int id;
    private double x;
    public static double sum;
    public static int n;
    private static Object mutex = new Object();

    MyThread(int id) {
        this.id = id;
    }

    public void run() {

        double ss=0;
        for(int i = id;i<n;i += 4) {

                x = (double) i / n;

                double f = 4/(1+x*x);

                double p = f /(double)n;

                ss =ss + p;

        }

        synchronized (mutex) {
            sum = sum + ss;
        }


    }
}