}

    private static void waitForQueryThreads(final QueryThread q1x, final QueryThread q20) {
        interruptThreadSafely(q1x);
        joinThread(q1x);
        interruptThreadSafely(q20);
        joinThread(q20);
    }

    private static void interruptThreadSafely(final QueryThread thread) {
        try {
            thread.interrupt();
        } catch (final SecurityException e) {