Lists with variables as their title

// Let me rephrase my problem since I might have found a better solution, I'm still stuck with it though.

For example can I create a list inside a config that starts off empty but then add I can add playernames to it without it requiring an actual list inside the code.

So for example you have a config named 'playername.yml', then I want to put an empty list inside named 'PartyMembers:'.

Now for example everytime uses a command '/paccept' (after checking, that part is all done) it will add the senders name to that list.

I can only see 'configname.set(PartyMembers, <playername>)' but I can't seem to find 'configname.add(PartyMembers, <playername)'. I know I could use '.set' to set a list inside PartyMembers, but there lies the problem. I can't make a list in the code because it would need to be unique per partyleader because every partyleader has different partymembers so I can't make a list named 'PartyMembers' and then keep adding names to it.

I hope someone can help.

Ok, I need it for a party system. I would like to make an array/list that has the partyleadersname as title and then the party members in the list. Is there anyway I could do this?

I recommend doing a separate class for your party, for the sake of OOP.
In that you could have a Player/String variable as party leader and a collection of party members.

Right but I have all my commands in the main class and that's where most of the adding is coming from, I don't really have alot of experience with implementing classes into eachother except for Listeners, or are they all listeners?

Still even with this I wouldnd be able to wrap my head around how it would change. I'll post the code so you know what I mean.

Code:

    @SuppressWarnings({ "unchecked", "unused" })
    @Override
    public boolean onCommand(CommandSender sender, Command cmd, String commandLabel, String[] args){
//another command
        else{
 
        if (cmd.getName().equalsIgnoreCase("createparty")) {
        Player player = (Player)sender;
        String playername = player.getPlayerListName();
        if(!HasParty.contains(playername)){
        YamlConfiguration PartyConfig = YamlConfiguration.loadConfiguration(new File(myNewDataFolder1,"[Party]"+playername+".yml"));
        HasParty.add(playername);
        IsPartyLeader.add(playername);
        }
        else{
        sender.sendMessage(ChatColor.RED + "You are already in a party."); 
        }
         
         
        return true; 
        }
     
        else{
         
        if (cmd.getName().equalsIgnoreCase("party")) {
            Player player = (Player)sender;
            String playername = player.getPlayerListName();
            if (args.length == 0) {
            sender.sendMessage(ChatColor.RED + "/party add/kick [playername]");
            }
            if (args.length == 1) {
            sender.sendMessage(ChatColor.RED + "/party add/kick [playername]"); 
            }
            if (args.length == 2) {
            if(args[0]=="add"){
            Player targetPlayer = player.getServer().getPlayer(args[1]);
            String targetPlayername = targetPlayer.getPlayerListName();
            if(targetPlayer==null){
            sender.sendMessage(ChatColor.RED + "Invalid playername."); 
            }
            else{
            if(HasParty.contains(targetPlayer)){
            sender.sendMessage(ChatColor.RED + "Player is already in a party.");
            }
            else{
            if(ActivePlayers.contains(targetPlayer)){
            if(ActivePlayers.contains(playername)){
            targetPlayer.sendMessage(ChatColor.RED + "invites you to his party. Type /paccept or /prefuse");
            HasInvitation.put(targetPlayername,true);
            YamlConfiguration PartyConfig = YamlConfiguration.loadConfiguration(new File(myNewDataFolder1,"[Party]"+targetPlayername+".yml"));
            PartyConfig.set("HasInvitation", HasInvitation.get(targetPlayername));
            PartyConfig.set("WhoInvitedPlayer", playername);
            }
            else{
            sender.sendMessage(ChatColor.RED + "Player is already inside the game."); 
            }
             
            }
            else{
            if(!ActivePlayers.contains(playername)){
                targetPlayer.sendMessage(ChatColor.RED + "invites you to his party. Type /paccept or /prefuse");
                HasInvitation.put(targetPlayername,true);
                YamlConfiguration PartyConfig = YamlConfiguration.loadConfiguration(new File(myNewDataFolder1,"[Party]"+targetPlayername+".yml"));
                PartyConfig.set("HasInvitation", HasInvitation.get(targetPlayername)); 
                PartyConfig.set("WhoInvitedPlayer", playername);
            }
            else{
            sender.sendMessage(ChatColor.RED + "Player is still in the lobby.");     
            }
            }
            }
            }
            }
            }
            return true;}
        else{
            if (cmd.getName().equalsIgnoreCase("p")) {
            if (args.length == 1) {
            if(args[0] == "accept"){
                YamlConfiguration PartyConfig = YamlConfiguration.loadConfiguration(new File(myNewDataFolder1,"[Party]"+sender+".yml"));
            Boolean HasInvitation = PartyConfig.getBoolean("HasInvitation");
            if(HasInvitation==true){
            String WhoInvitedPlayer = PartyConfig.getString("WhoInvitedPlayer");
            YamlConfiguration Party = YamlConfiguration.loadConfiguration(new File(myNewDataFolder1,"[Party]"+WhoInvitedPlayer+".yml"));
            //This is where a player should be added to the partymembers list.
            }
            }
            }
         
            return true;
            }
         
        }
        }
  }
return false; }

Can anyone help?

Start by getting the list from the yaml, then add the player to that list, then save it to the file.

God, that's so simple why didn't I think about that O.O Thanks alot