how to avoid pack()

import java.awt.*;
import javax.swing.*;

public class Screen extends JFrame{

	//Panels for all buttons////////////////
	private JPanel computer;
	private JPanel parts;
	private JPanel sound;
	private JPanel screens;
	private JPanel misc;
	private JPanel misc2;
	///////////////////////////////
	
	private String path;

	//////////LABELS//////////////////
	private JButton computere;
	private JButton parte;
	private JButton sounde;
	private JButton screene;
	private JButton misce;
	private JButton misc2e;
	
	private ImageIcon compImg;
	private ImageIcon partsImg;
	
	private JLabel computerLabel;
	private JLabel partsLabel;
	
	Screen()
	{
		setLayout(new GridLayout(2,2));
		setSize(800,800);
		setTitle("Inventory");
		setDefaultCloseOperation(EXIT_ON_CLOSE);
		setVisible(true);
		
		iniVars();
		
		addPanels();
	}
	
	
	public void iniVars()
	{
		iniLabels();
		iniImages();
		iniButtons();
		iniJpanels();
		addToPanels();
	}
	
	public void iniButtons()
	{
		
		computere = new JButton(compImg);
		parte = new JButton(partsImg);
		sounde = new JButton();
		screene = new JButton();
		misce = new JButton();
		misc2e = new JButton();
		
		computere.setPreferredSize(new Dimension(300,300));
		parte.setPreferredSize(new Dimension(300,300));
			
	}
	
	public void iniImages()
	{
		compImg = new ImageIcon("comp.jpg");
		partsImg = new ImageIcon("harddrive.jpg");
	}
	
	public void addToPanels()
	{
		computer.add(computere);
		parts.add(parte);	
	}
	
	public void iniJpanels()
	{
		computer = new JPanel();
		parts = new JPanel();
	}
	
	
	public void iniLabels()
	{
		computerLabel = new JLabel("Computers");
		partsLabel = new JLabel("Parts");
		computerLabel.setPreferredSize(new Dimension(30,30));
		partsLabel.setPreferredSize(new Dimension(30,30));
		
	}
	public void addPanels()
	{
		add(computerLabel);
		add(partsLabel);
		add(computer);
		add(parts);
		
		pack();
	}
	
}//End of class Screen