Instância de objetos em Java

import java.awt.Container;
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.WindowConstants;
import javax.swing.SwingUtilities;

public class UserInterface implements Runnable {

    private JFrame frame;

    public UserInterface() {
    }

    @Override
    public void run() {
        frame = new JFrame("Title");
    	frame.setPreferredSize(new Dimension(200, 100));

        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        createComponents(frame.getContentPane());

        frame.pack();
        frame.setVisible(true);	
    }

	    private void createComponents(Container container) {
	    }

	    public JFrame getFrame() {
	        return frame;
	    }
	}
public class Main {

    public static void main(String[] args) {
        UserInterface ui = new UserInterface();
    	SwingUtilities.invokeLater(ui);
    }
}