Solved How to include a command in the main file?

Hello, I am just starting with coding with spiggot. I can not understand how to include the command that I have created in onEnable() (in the main file, of course). the only way I could find online that doesn't work anymore is attached, the errors are in Main: line 11 and in HelloCommand: line 15. I will be grateful for any help!

Code:

package me.robertlit.helloworld.commands;

import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import me.robertlit.helloworld.Main;

public class HelloCommand implements CommandExecutor {

    private Main plugin;

    public HelloCommand(Main plugin) {
        this.plugin = plugin;
        plugin.getCommand("hello").setExecutor(this);
    }

    @Override
    public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {
        if (!(sender instanceof Player)) {
            sender.sendMessage("You do not have the permission to execute this command!");
            return true;
        }
    
        Player p = (Player) sender;
    
        if (p.hasPermission("hello.use")) {
            p.sendMessage("Hey!");
        } else {
            p.sendMessage("You do not have permission to execute this command!");
        }
        return false;
    }


}

Code:

package me.robertlit.helloworld;

import org.bukkit.plugin.java.JavaPlugin;

import me.robertlit.helloworld.commands.HelloCommand;

public class Main extends JavaPlugin {

    @Override
    public void onEnable() {
        new HelloCommand(this);
    }
}

 

@timtower
Errors are at Erroes.png
Line 15 in HelloCommand is:

Code:

plugin.getCommand("hello").setExecutor(this);

Line 11 in Main is

Code:

new HelloCommand(this);

This is the plugin.yml

Code:

name: HelloWorld
version: 1.8.8
author: robertlit
main: me.robertlit.helloworld.Main

I don't have the command in the plugin.yml file since I thought that this is not necessary. (https://bukkit.gamepedia.com/Plugin_YAML says that this is unnecessary)

EDIT: I just added the command into my plugin.yml file and it worked! Thank you.

 

Thanks. solved.