JFrame does not hide when setVisible(false)

Question

import javax.swing.*;

class Frame extends JFrame{
    Frame() {
        JFrame j = new JFrame();
        j.setBounds(100, 200, 120, 120);
        j.setTitle("null");
        j.setVisible(true);
        j.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    }
}

public class test001 {

    public static void main (String Args[]){
        Frame f = new Frame();
         System.out.print("Visible = True");

        f.setVisible(false);
        System.out.print("Visible = false");
    }
}

after the setVisible(false) command. The JFrame Window still show on my desktop. How can I fix that ?

Answer 1

You're creating another JFrame within your constructor. Assuming what you want is your Frame class to be invisible, do this:

class Frame extends JFrame {

   Frame() {
      setBounds(100, 200, 120, 120);
      setTitle("null");
      setVisible(true);
      setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
   }
}

public class test001 {

   public static void main(String Args[]) {
      Frame f = new Frame();
      System.out.print("Visible = True");

      f.setVisible(false);
      System.out.print("Visible = false");
   }
}

Answer 2

Problem is that your main method uses different JFrame that your constructor. Your Frame constructor creates new JFrame instance (using new JFrame). When you call f.setVisible(false), it goes to your frame, but not to created JFrame.

Answer 3

The problem here is that your "Frame" class instanciates a new JFrame. Calling setVisible on the Frame does not affect the JFrame which is being shown.

You can fix it by either just using a JFrame instance, or just subclassing. Don't do both.