Code

@Override
public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {
    if (cmd.getLabel().equalsIgnoreCase("freeze")) {
        if (!sender.hasPermission("zirconessentials.freeze")) {
            sender.sendMessage(ChatColor.RED + "You do not have permission to freeze players!");
        } else {
            if (args.length < 1) {
                sender.sendMessage(ChatColor.RED + "Please specify a player to freeze!");
            }
            if (args.length >= 1) {
                if (Bukkit.getPlayer(args[0]) != null) {
                    frozen.put(Bukkit.getPlayer(args[0]).getUniqueId(), Bukkit.getPlayer(args[0]).getLocation());
                    if (Bukkit.getPlayer(args[0]) != sender) {
                        Bukkit.getPlayer(args[0]).sendMessage(ChatColor.BLUE + "You have been frozen by " + sender);
                        sender.sendMessage(ChatColor.BLUE + "You froze " + Bukkit.getPlayer(args[0]));
                    } else {
                        sender.sendMessage(ChatColor.BLUE + "You froze yourself!");
                    }
                } else {
                    sender.sendMessage(ChatColor.RED + "The specified player could not be found!");
                }
            }
        }
        return true;
    } else if (cmd.getLabel().equalsIgnoreCase("unfreeze")) {
        if (!sender.hasPermission("zirconessentials.unfreeze")) {
            sender.sendMessage(ChatColor.RED + "You do not have permission to unfreeze players!");
        } else {
            if (frozen.containsKey(Bukkit.getPlayer(args[0]).getUniqueId())) {
                frozen.remove(Bukkit.getPlayer(args[0]).getUniqueId());
                if (Bukkit.getPlayer(args[0]) != sender) {
                    Bukkit.getPlayer(args[0]).sendMessage(ChatColor.BLUE + "You have been frozen by " + sender);
                    sender.sendMessage(ChatColor.BLUE + "You unfroze " + Bukkit.getPlayer(args[0]));
                } else {
                    sender.sendMessage(ChatColor.BLUE + "You unfroze yourself!");
                }
            }
        }
        return true;
    }
    return false;
}