What is causing an internal error here?

Code:

import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.inventory.ItemStack;
import org.bukkit.inventory.meta.ItemMeta;

public class Rename implements CommandExecutor {
    @SuppressWarnings("deprecation")
    public boolean onCommand(CommandSender sender, Command cmnd, String cmndlabel, String[] args) {
        if (!(sender instanceof Player)) {
            sender.sendMessage("You must be a player to perform this command!");
            return false;
        }
        Player player = (Player) sender;
        ItemMeta meta = player.getInventory().getItemInMainHand().getItemMeta();
        meta.setDisplayName(args[0]);
        ItemStack stack = (ItemStack) meta;
        player.setItemInHand(stack);
        return true;
    }

}

 

@niehoelzz

1. The Item may not exist.
2. The item meta may not exist.
3. You are not checking the args length. Make sure there are args before you get the first one.
4. You cannot convert ItemMeta to an Itemstack. Create a new ItemStack or just get the item in the main and and re-set its item meta.