Cyclic barrier download

Main.java

package com.company;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.Queue;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.CyclicBarrier;

public class Main {
    static class Task implements Runnable {
        private final int executionTimeMs;

        Task(int executionTimeMs) {
            this.executionTimeMs = executionTimeMs;
        }

        @Override
        public void run() {
            try {
                System.out.println("I am " + toString());
                Thread.sleep(executionTimeMs);
            }
            catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    private static class DownloadTask extends Task {
        private final int index;

        DownloadTask(int index) {
            super((int)(Math.random() * 1000.0));
            this.index = index;
        }

        @Override
        public String toString() {
            return getClass().getSimpleName() + " " + index;
        }
    }

    private static class InstallTask extends Task {
        private final int index;

        InstallTask(int index) {
            super((int)(Math.random() * 2000.0));
            this.index = index;
        }

        @Override
        public String toString() {
            return getClass().getSimpleName() + " " + index;
        }
    }


    private static Collection<DownloadTask> downloadTasks = new ArrayList<>();
    private static Queue<InstallTask> installTasks = new ConcurrentLinkedQueue<>();

    private static CyclicBarrier barrier = new CyclicBarrier(2);


    private static void downloadTasksExecutor() {
        for (Iterator<DownloadTask> iterator = downloadTasks.iterator(); iterator.hasNext(); ) {
            final DownloadTask t = iterator.next();

            t.run();
            installTasks.add(new InstallTask(t.index));

            if (barrier.getNumberWaiting() == 1) {
                try {
                    barrier.await();
                } catch (InterruptedException | BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }

            iterator.remove();
        }

        System.out.println("downloadTasksExecutor finished");
    }

    private static void installTasksExecutor() {
        while (!downloadTasks.isEmpty()) {
            try {
                barrier.await();
            } catch (InterruptedException | BrokenBarrierException e) {
                e.printStackTrace();
            }

            InstallTask t;
            while ((t = installTasks.poll()) != null)
                t.run();
        }

        System.out.println("installTasksExecutor finished");
    }


    public static void main(String[] args) throws Exception
    {
        for (int i = 0; i < 10; i++)
            downloadTasks.add(new DownloadTask(i));

        final Thread downloadThread = new Thread(Main::downloadTasksExecutor);
        final Thread installThread = new Thread(Main::installTasksExecutor);


        downloadThread.start();
        installThread.start();

        installThread.join();
    }
}