private class Abecadlo implements Runnable {

    static BlockingQueue<String> queue = new LinkedBlockingQueue();
        @Override
        public void run() {
            while (true) {
                String s = queue.take();

        // zrób coś z tym stringiem
            }
        }
}

public void setStringToShow(String stringToShow) {
    // coś tam
    Abecadlo.queue.put(stringToShow);
}