private final static NamespacedKey KEY = new NamespacedKey(Main.get(),"some_key");
	@Override
	public void onExecute(CommandSender sender, String alias, String[] args) {
		Player p = (Player) sender;
		Item item = p.getWorld().dropItem(p.getLocation().add(0,15,0), new ItemStack(Material.DIRT));
		item.getPersistentDataContainer().set(KEY, PersistentDataType.STRING, "some_value");
		Bukkit.broadcastMessage(item.getUniqueId()+" (created)");
	}
	
	@EventHandler
	public void event(EntityPickupItemEvent event) {
		Bukkit.broadcastMessage(event.getItem().getUniqueId()+" has metadata? "+event.getItem().getPersistentDataContainer().has(KEY, PersistentDataType.STRING));
	}