Vanish command

I've been creating a vanish plugin, but whenever I type sender in to eclipse it shows up with red lines under it, this also happens when I type cmd, here is the plugin.

Code:

package me.Funnylizard99.vanishcommand;

import java.util.ArrayList;

import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerJoinEvent;
import org.bukkit.event.player.PlayerQuitEvent;
import org.bukkit.plugin.java.JavaPlugin;

public class Main extends JavaPlugin implements Listener {
  
    public void onEnable(){
        Bukkit.getServer().getPluginManager().registerEvents(this,  this);
      
      
    }

    private ArrayList<Player> vanished = new ArrayList<Player>();
  

    @Override
    public boolean onCommand(CommandSender arg0, Command arg1, String arg2, String[] arg3) {
        if (sender instanceof Player) {
           (this is one of the senders with a red line under it)
            Player p = (Player) sender;
                                                (This is one of the senders with a red line under it)
            if (cmd.getname().equalsIgnoreCase("vanish")) {
               (This is the cmd with the red line under it)
              
                if (!vanished.contains(p))
              
                for(Player pl : Bukkit.getOnlinePlayers()){
                    pl.hidePlayer(p);
                }
                vanished.add(p);
                p.sendMessage(ChatColor.GREEN + "Vanish enabled");
                return true;
            }
      
            else {
              
                for(Player pl : Bukkit.getOnlinePlayers()){
                    pl.showPlayer(p);
                }
                vanished.remove(p);
                p.sendMessage(ChatColor.GREEN + "Vanish disabled");
                return true;

            }
        }

        return true;
    }
    @EventHandler
    public void onPlayerJoin(PlayerJoinEvent e) {
        for (Player p : vanished) {
            e.getPlayer().hidePlayer(p);
          
          
        }
    }
  
    @EventHandler
    public void onPLayerLeave(PlayerQuitEvent e) {
        vanished.remove(e.getPlayer());
    }

}

Your help is appreciated

 

One of the flaws of auto generated methods; the method names may not always carry over. In this case, "sender' is replaced with arg0. Go through the onCommands parameters and rename all the variables.

 

@Funnylizard99
You're command boolean is incorrect. You have

Code:

public boolean onCommand(CommandSender arg0, Command arg1, String arg2, String[] arg3) {

That would mean you would do Player p = (Player) arg0; for future reference.
The "correct" boolean or whatever is

Code:

public boolean onCommand(CommandSender sender, Command cmd, String alias, String[] args) {