TrackingCommandsExecutor.java

public class TrackingCommandsExecutor implements Executor {

    private final Queue<CountDownLatch> commandLatches = new ConcurrentLinkedQueue<>();
    private final Executor delegate;

    public TrackingCommandsExecutor(Executor delegate) {
        this.delegate = delegate;
    }

    @Override
    public void execute(@NonNull Runnable command) {
        CountDownLatch latch = new CountDownLatch(1);
        commandLatches.add(latch);

        Runnable trackedCommand = () -> {
            command.run();
            latch.countDown();
        };

        delegate.execute(trackedCommand);
    }

    public void waitCommands() throws InterruptedException {
        CountDownLatch latch;
        while ((latch = commandLatches.poll()) != null) {
            try {
                latch.await();
            } catch (InterruptedException e) {
                commandLatches.add(latch);
                throw e;
            }
        }
    }
}