public class Main extends JavaPlugin implements Listener{

    DateFormat dFormat = new SimpleDateFormat("HH:mm");
    Date d = new Date();


    public void onEnable() {
        System.out.println("[BookshelfDrop] BookshelfDrop v" + this.getDescription().getVersion() + " enabled");
        getServer().getPluginManager().registerEvents(this, this);


    }

    public void onDisable() {
        System.out.println("[BookshelfDrop] BookshelfDrop disabled");
    }




    @EventHandler
    public void onChange(SignChangeEvent event) {

        if (event.getLine(0).equalsIgnoreCase("[clock]")) {
            Sign s = (Sign) event.getBlock().getState();
            s.setLine(0, "[clock]");
            Bukkit.getServer()
                    .getScheduler()
                    .scheduleSyncRepeatingTask(
                            Bukkit.getPluginManager().getPlugin("BookshelfDrop"),
                            new Runnable() {

                                public void run() {
                                    s.setLine(1, "§a" + dFormat.format(d));
                                    s.update();
                                }
                            }, 0, 20L);
        }
    }