Java – how to change the JFrame content to the corresponding click?

I am using java to develop a simple desktop application There is a menu bar. When the user clicks menu item 1, the content will become form A. when the user clicks menu item 2, the content will display form B

How can I achieve this goal?

Use the same window, only the content changes

Solution

A sample for you, I just refreshed my swing knowledge

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;

public class FrmChange extends JFrame{

private JPanel panel1 = new JPanel();
private JPanel panel2 = new JPanel();

public FrmChange(){
    setDefaultCloSEOperation(EXIT_ON_CLOSE);
    initMenu();
    panel1.setBackground(Color.BLUE);
    panel2.setBackground(Color.RED);
    setLayout(new BorderLayout());
}

private class MenuAction implements ActionListener {

    private JPanel panel;
    private MenuAction(JPanel pnl) {
        this.panel = pnl;
    }
    @Override
    public void actionPerformed(ActionEvent e) {
        changePanel(panel);

    }

}

private void initMenu() {
    JMenuBar menubar = new JMenuBar();
    JMenu menu = new JMenu("Menu");
    JMenuItem menuItem1 = new JMenuItem("Panel1");
    JMenuItem menuItem2 = new JMenuItem("Panel2");
    menubar.add(menu);
    menu.add(menuItem1);
    menu.add(menuItem2);
    setJMenuBar(menubar);
    menuItem1.addActionListener(new MenuAction(panel1));
    menuItem2.addActionListener(new MenuAction(panel2));

}

private void changePanel(JPanel panel) {
    getContentPane().removeAll();
    getContentPane().add(panel,BorderLayout.CENTER);
    getContentPane().doLayout();
    update(getGraphics());
}

public static void main(String[] args) {
    FrmChange frame = new FrmChange();
    frame.setBounds(200,200,300,200);
    frame.setVisible(true);

}

}