How to make my JFrame on the top op the screen?

Question

I will launch Window2 after I click a button. It's not launched immediately but after 3 seconds. What I want is to show it on the top of the screen. It works if the Window1 is still on the screen but fails if I minimize Window1.

The code is here:

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class TopTest {
    public static void main(String[] args) {
        TopTest test = new TopTest();
        test.createUI();
    }

    public void createUI(){
        JFrame frame = new JFrame("Window1");
        JPanel panel = new JPanel();
        JButton button = new JButton("show");
        button.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                // TODO Auto-generated method stub
                Window window = new Window();
                try {
                    Thread.sleep(3000);
                } catch (InterruptedException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
                window.createUI();
            }
        });
        panel.add(button);
        frame.add(panel,BorderLayout.CENTER);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    class Window {
        public void createUI(){
            JFrame frame = new JFrame("Window2");
            frame.setExtendedState(Frame.MAXIMIZED_BOTH);
            frame.add(new MainPanel());
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        }

        @SuppressWarnings("serial")
        class MainPanel extends JPanel{
            @Override
            public Dimension getPreferredSize() {
                // TODO Auto-generated method stub
                return new Dimension(800,600);
            }

            protected void paintComponent(Graphics g){
                g.setFont(new Font("Arial", Font.BOLD, 50));
                g.drawString("I am Window2", 200, 200);
            }
        }
    }
}

Thanks for your help in advance.

Answer 1

将此行添加到createGUI方法

frame.setAlwaysOnTop(true);