Código

package me.leozinhoplay.com;

import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.plugin.java.JavaPlugin;

public class Main extends JavaPlugin
{
  public void onEnable()
  {
    getServer().getConsoleSender().sendMessage("§bAtivando Fly.");
    getServer().getConsoleSender().sendMessage("§bFly Ativado.");
    saveDefaultConfig();
  }

  public void onDisable() {
    getServer().getConsoleSender().sendMessage("§4Desativando Fly.");
    getServer().getConsoleSender().sendMessage("§4Desativado Fly.");
  }

@Override
	public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
		if (sender instanceof Player) {
			Player p = (Player)sender;
			if (label.equalsIgnoreCase("fly")) {
				if (p.hasPermission("fly.usar")) {
					if (p.isFlying()) {
						p.setFlying(false);
						p.sendMessage("§cFly desativado!");
					} else {
						p.setFlying(true);
						p.sendMessage("§cFly ativado!");
					}
				} else {
					p.sendMessage("§cSem permissão!");
					return true;
				}
			}
		}
		return false;
	}
}