import javax.swing.*;
import java.awt.*;
public class jobDoor {

	JFrame frame;
	JPanel primary, mainPanel;

	public void windowPopper (String args) {
		String argument = args;

		sidePanel side = new sidePanel();
		frame = new JFrame();
		primary = new JPanel();
		mainPanel = new JPanel();
		if (argument.equals("starfsmenn")) {
			starfsmenn starfsm = new starfsmenn();
			mainPanel.add(starfsm.smenn());
		}
		primary.add(side.sPane());
		primary.add(mainPanel);
		mainPanel.setPreferredSize(new Dimension(500, 500));
		frame.getContentPane().add(primary);
		frame.setLocationRelativeTo(null);
		frame.pack();
		frame.setVisible(true);
	}
	public void closeWindow() {
		frame.setVisible(false);
		frame.dispose();
	}
}

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class sidePanel {
		JButton starfsmenn, vaktatafla, laun, veikindi;

		public Component sPane() {
			JPanel sidebar = new JPanel();
			JLabel empty  = new JLabel(" ");
			JLabel empty2 = new JLabel(" ");
			JLabel empty3 = new JLabel(" ");

			starfsmenn	= new JButton("Starfsmenn");
			vaktatafla	= new JButton("Vaktatafla");
			laun		= new JButton("Launakerfi");
			veikindi	= new JButton("Veikindi/frí");

			sidebar.setLayout(new BoxLayout(sidebar, BoxLayout.Y_AXIS));
			buttonListener listen = new buttonListener();

			starfsmenn.addActionListener(listen);
			vaktatafla.addActionListener(listen);
			laun.addActionListener(listen);
			veikindi.addActionListener(listen);

			sidebar.add(starfsmenn);
			sidebar.add(empty);
			sidebar.add(vaktatafla);
			sidebar.add(empty2);
			sidebar.add(laun);
			sidebar.add(empty3);
			sidebar.add(veikindi);

			return sidebar;
		}
		public class buttonListener implements ActionListener {
			public void actionPerformed (ActionEvent e) {
				if(e.getSource() == starfsmenn) {
						//
						// HERE IS MY PROBLEM
						//
					jobDoor.closeWindow();
					jobDoor.windowPopper("starfsmenn");
						//
						// AND ENDS HERE(hopefully)
						//
				}

			}
		}
}