EventBus

    static volatile EventBus defaultInstance;

    public static EventBus getDefault() {
       if (defaultInstance == null) {
           synchronized (EventBus.class) {
               if (defaultInstance == null) {
                   defaultInstance = new EventBus();
               }
           }
       }
       return defaultInstance;
    }

Universal-Image-Loader

    private volatile static ImageLoader instance;

    public static ImageLoader getInstance() {
        if (instance == null) {
            synchronized (ImageLoader.class) {
                if (instance == null) {
                    instance = new ImageLoader();
                }
            }
        }
        return instance;
    }

    protected ImageLoader() {
    }