JPaneller arası geçiş nasıl yapılabilir?

package gui;

import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;

@SuppressWarnings("serial")
public class Form_Main extends JFrame {

	/**
	 * Launch the application.
	 */
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					Form_Main frame = new Form_Main();
					frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}

	/**
	 * Create the frame.
	 */
	public Form_Main() {
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setBounds(100, 100, 450, 300);

		JPanel pg = new Panel_Giris();
		panelEkle(pg);
	}

	public void panelEkle(JPanel j) {
		j.setBorder(new EmptyBorder(5, 5, 5, 5));
		j.setLayout(null);
		setContentPane(j);
	}

}

package gui;

import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

@SuppressWarnings("serial")
public class Panel_Giris extends JPanel {
	private JTextField textField;
	private JTextField textField_1;

	/**
	 * Create the panel.
	 */
	public Panel_Giris() {
		setLayout(null);
		
		JLabel lblNewLabel = new JLabel("New label");
		lblNewLabel.setBounds(68, 95, 70, 15);
		add(lblNewLabel);
		
		textField = new JTextField();
		textField.setBounds(177, 93, 114, 19);
		add(textField);
		textField.setColumns(10);
		
		JLabel lblNewLabel_1 = new JLabel("New label");
		lblNewLabel_1.setBounds(68, 143, 70, 15);
		add(lblNewLabel_1);
		
		textField_1 = new JTextField();
		textField_1.setBounds(177, 141, 114, 19);
		add(textField_1);
		textField_1.setColumns(10);
		
		JButton btnNewButton = new JButton("New button");
		btnNewButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent arg0) {
				Form_Main fm = new Form_Main();
				JPanel ana = new Panel_A();
				fm.panelEkle(ana);
			}
		});
		btnNewButton.setBounds(177, 193, 117, 25);
		add(btnNewButton);

	}
}