How to make commands with subcommands in spigot plugins?

Question

So I'm trying to make a command with subcommands
command examples:

/its heal (player)
/its feed (player)
/its help

Here is my main plugin file code if needed:

    package com.itsmateo20;
    
    import com.itsmateo20.events.JoinQuit;
    import org.bukkit.Bukkit;
    import org.bukkit.ChatColor;
    import org.bukkit.configuration.file.FileConfiguration;
    import org.bukkit.plugin.java.JavaPlugin;
    
    public class ItsPlugin20 extends JavaPlugin {
        private static ItsPlugin20 instance;
    
    
        @Override
        public void onEnable() {
            instance = this;
            FileConfiguration config = getConfig();
            config.addDefault("Prefix", "[ItsPlugin20]:");
            config.addDefault("JoinQuit", true);
            config.options().copyDefaults(true);
            saveConfig();

            if (config.getBoolean("JoinQuit")) {
                Bukkit.getPluginManager().registerEvents(new JoinQuit(), this);
            }
            Bukkit.getLogger().info(config.getString("Prefix") + ChatColor.GREEN + " Enabled successfully!");
        }
    
        @Override
        public void onDisable() {
            FileConfiguration config = getConfig();
            Bukkit.getLogger().info(config.getString("Prefix") + ChatColor.RED + " Disabled successfully!");
        }
    
        public static ItsPlugin20 getInstance() {
            return instance;
        }
    }

Answer 1

Firstly, you have to register your command in your plugin.yml file :

commands:
   its:
      description: "Made things"

Then, to use it in your plugin, in the onEnable() method :

getCommand("its").setExecutor(new ItsCommand());

After this, you should create the class ItsCommand and make the complete command, with all sub commands. Spigot don't have a very good API for this. The class should look like that :

public class ItsCommand implements CommandExecutor {

    @Override
    public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
        return false;
    }
}

The method will be called each time the command will be runned.

1. The sender can be the console, a command block or the player. We should check by using :

if(!(sender instanceof Player)) {
   sender.sendMessage("Only players can run this command !");
   return false;
}

2. The command is globally never used.
3. The label correspond to the exact command that the player runned (to know if it's "/plugin:its", "/its" ...)
4. The args are what you are looking for.

You should check if it's empty with args.length == 0, and so the player just use "/its". You can show the help.

Then, you should check what is the argument, like args[0].equalsIgnoreCase("feed").

Complete example of the method :

@Override
public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
    if(!(sender instanceof Player)) {
        sender.sendMessage("Only players can run this command !");
        return false;
    }
    Player p = (Player) sender;
    if(args.length == 0 || args[0].equalsIgnoreCase("help")) { // if no args or help
        showHelp(p);
    } else if(args[0].equalsIgnoreCase("feed")) { // if the first arg is what you want
        if(args.length == 1) { // only run "/its feed" without player
            p.sendMessage(ChatColor.RED + "You forget the player name !");
            return false;
        }

        Player cible = Bukkit.getPlayer(args[1]); // get the player given
        if(cible == null){ // player not online/invalid
            p.sendMessage(ChatColor.RED + "The given player doesn't exist !");
        } else {
            cible.setFoodLevel(20); // do what you want with the cible
            p.sendMessage(ChatColor.GREEN + "Player feeded !");
        }
    } else { // unknow sub command
        p.sendMessage(ChatColor.RED + "Unknow arguments !");
        showHelp(p);
    }
    return false;
}