So Simple!

if(cmd.getName().equalsIgnoreCase("ban")) {
    if(args.length == 1) {
        Player target = Bukkit.getPlayer(args[0]);
        if(target.isOnline()) {
            // Kick Them
            // Ban Them
            // Broadcast Message
            return true;
        } else {
            OfflinePlayer offlineTarget = Bukkit.getOfflinePlayer(args[0]);
            // Ban Them
            // Broadcast Message
            return true;
        }
    }
}