ArrayList Error Help

I am getting an error whenever I try to do this, and have had this problem for a while. Anybody help??

Code:

public boolean onCommand(CommandSender sender, Command cmd, String commandLabel, String[] args) {
        if (cmd.getName().equalsIgnoreCase("warn")) {
            if (args.length == 0) {
                sender.sendMessage(ChatColor.DARK_RED + "Please specify a player.");
                return true;
            }
            Player target = Bukkit.getServer().getPlayer(args[0]);
            if (target == null) {
                sender.sendMessage(ChatColor.DARK_RED + "The player " + args[0] + " is not on the server.");
            }
            if (!warned1.contains(target.getName())) {
                target.sendMessage(ChatColor.RED + "You have recieved a warning from " + sender.getName() + "\n" + args[1]);
                warned1.add(target.getName());
                return true;
            }
        }
        return true;
    }   
}

 

Tag me in with the error, you post.

 

Failure to post the error?

I would use UUIDs rather than player names. Players can just evade warnings by changing their name with your code. I would also use a Set rather than a List. Sets don't allow duplicates which will negate the need for you to do such things like this:

Code:

if (!warned1.contains(target.getName()))