potok

import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        potok R = new potok();
        int menu;
        do{
            System.out.println("Enter menu");
            System.out.println("1. Start");
            System.out.println("2. Continue");
            System.out.println("3. Pause");
            System.out.println("4. Print");
            System.out.println("5. Print time");
            System.out.println("0. Exit");
            menu = in.nextInt();
            switch(menu){
                case 1:
                    R.start();
                    break;
                case 2:
                    synchronized(R){
                        R.notify();
                    }
                    R.FlPause = false;
                    break;
                case 3:
                    R.FlPause = true;
                    break;
                case 4:
                    System.out.println(R.getPi());
                    break;
                case 5:
                    R.getTime();
                    break;
            }
        }while(menu != 0);
    }
}
import java.lang.Math;

public class potok extends Thread {
    public volatile boolean FlPause = false;
    public boolean FlCoun = true;
    public double pi = 0;
    volatile long timeStart;
    volatile long timeSpend;
    volatile long time;

    @Override
    public void run() {
        long i = 0;
        timeStart = System.currentTimeMillis();

        while (FlCoun) {
            pi = pi + (Math.pow(-1, i) / (2 * i + 1));
            i++;

            if (FlPause) {
                timeSpend = System.currentTimeMillis() - timeStart;
                time += timeSpend;
                try {
                    synchronized (this){
                        wait();
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }

    }


    public double getPi() {
        return (4 * pi);
    }

    public void getTime() {
        System.out.println("Seconds: " + time/1000);
        time = 0;
    }
}