org.bukkit.plugin.InvalidPluginException: main class does not extend JavaPlugin

Hello,
I try to create my first plugin but everytime I try to install it I see this error message: org.bukkit.plugin.InvalidPluginException: main class [...].Main does not extend JavaPlugin. I have already checked plugin.yml and my main class (main.java) but:

  • I wrote main: [...].Main
  • I imported org.bukkit.[...].JavaPlugin
  • I extended JavaPlugin

Her’s some Code:


plugin.yml

name: my_name_here
version: 1.0
author: Another name
main: example.thatsme.plugin_name.Main

commands:
  acommand:
    aliases: [ac]

Main.java

package example.thatsme.plugin_name;

import org.bukkit.plugin.java.JavaPlugin;

import example.thatsme.plugin_name.commands.A_command;

public class Main extends JavaPlugin {
	
	@Override
	public void onEnable() {
		new A_command(this);
	}
}


And ther’s commands/A_command.java. I think I don’t need to show this as well.