Java Error: When Calling a Different Class in the Main method but Runs Fine when compiled same class with the main method

Question

I am trying to compile this code on CMD.

public class Main {

    public static void main(String[] args){
        new HelloWorld("Main Window");
    }
}

this is the HelloWorld class

import javax.swing.JFrame;

public class HelloWorld extends JFrame{

    public HelloWorld(String title){
        super(title);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
     }
}

but it is giving me an error like CMD snap shot

but when I instantiate HelloWorld in the same class with the main method, it runs fine.