PriemGetallenCallable.java

package hfdst4;
import java.util.*;
import java.util.concurrent.*;

class PriemZoekerCallable implements Callable<ArrayList<Integer>> {
    protected int start,einde;
    public PriemZoekerCallable(int start, int einde) {
        this.start = start;
        this.einde = einde;
        System.out.println("Priemdraad: #"+start+" -> "+ einde+" aangemaakt !");
    }
    @Override
    public ArrayList<Integer> call() {
        ArrayList<Integer> r = new ArrayList<>();
        for (int n = start; n <= einde; n++) {
            if (n >= 2) {
                boolean flag = true;
                for (int i = 2; i <= Math.sqrt(n); i++) {
                    if (n%i == 0) {
                        flag = false;
                        break;
                    }
                }
                if (flag == true) {
                    // System.out.println("Priemgetal: " + n);
                    r.add(n);
                }
            }
        }
        return r;
    }
}

class TestPriemCallable {
    public static void main(String[] args) {
        int N = 1000;
        int nTaken = 10;
        int interval = N/nTaken;
        ExecutorService e = Executors.newCachedThreadPool();
        Future[] f = new Future[nTaken];

        for (int i = 0; i < nTaken; i++) {
            // PriemZoekerCallable priemzoeker = new PriemZoekerCallable(i*interval, (i+1)*interval);
            // list[i] = priemzoeker.call();
            f[i] = e.submit(new PriemZoekerCallable(i*interval, (i+1)*interval));
        }

        e.shutdown();

        for (Future i : f) {
            try {
                System.out.println(i.get());
            } catch(Exception ex) {
                ex.printStackTrace();
            }
        }

    }
}