import java.util.concurrent.CountDownLatch;

public class CountDownLatchEksempel {

    public static void main(String[] args) {

        int numThreads = 10;

        Thread[] traader = new Thread[numThreads];

        CountDownLatch start = new CountDownLatch(1);
        CountDownLatch halvveis = new CountDownLatch(numThreads);
    
        for (int i = 0; i < 10; i++) {
            traader[i] = new Thread(new CountDownArbeider(i, start, halvveis));
            traader[i].start();
        }

        System.out.println("Starter tr?der...");

        start.countDown();

        System.out.println("Venter p? tr?der...");

        try {
            halvveis.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println("Venter p? tr?der igjen...");

        for (Thread t : traader) {
            try {
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        System.out.println("Alle tr?der er ferdige!");
    }
}

class CountDownArbeider implements Runnable {

    int id;
    CountDownLatch startSignal, halvveisSignal;

    public CountDownArbeider(int id, CountDownLatch startSignal, CountDownLatch halvveisSignal) {
        this.id = id;
        this.startSignal = startSignal;
        this.halvveisSignal = halvveisSignal;
    }

    @Override
    public void run() {

        try {
            startSignal.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.printf("Tr?d %d gjennomf?rer f?rste del av arbeidet.%n", id);

        try {
            // Simulerer at tr?den bruker tid p? ? jobbe
            Thread.sleep((int) (Math.random() * 1000));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        halvveisSignal.countDown();

        try {
            halvveisSignal.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.printf("Tr?d %d gjennomf?rer andre del av arbeidet.%n", id);

        try {
            // Simulerer at tr?den bruker tid p? ? jobbe
            Thread.sleep((int) (Math.random() * 1000));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.printf("Tr?d %d er ferdig!%n", id);
    }
}