@EventHandler(priority = EventPriority.MONITOR)
    public void onSignInteract(PlayerInteractEvent event) {
        if (event.getAction() == Action.RIGHT_CLICK_BLOCK) {
            if ((event.getClickedBlock() != null) && (event.getClickedBlock().getType() == Material.SKULL)) {

                Skull sk = (Skull) event.getClickedBlock().getState();

              //If the skull is a player do this
              if (sk.getSkullType() == SkullType.PLAYER) {
                    event.getPlayer().sendMessage(ChatColor.GRAY + "Head of " + ChatColor.WHITE + sk.getOwner() + ChatColor.YELLOW + ".");
              }

              //If the skull is NOT a player
              if (!sk.getSkullType() == SkullType.PLAYER) {
                    event.getPlayer().sendMessage(ChatColor.GRAY + "Head of " + ChatColor.WHITE + sk.getOwner() + ChatColor.YELLOW + ".");
              }
            }
        }
    }