为什么这段代码无法在显示子窗口的时候隐藏父窗口并且抛出了异常

源代码:

package main;
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

class subswing extends JFrame{
    public subswing(){
        setTitle("child JFrame");
        JLabel jLabel = new JLabel("This is the child JFrame~");
        jLabel.setBounds(150,170,100,100);
        getContentPane().add(jLabel);
        pack();
    }
}

class swing extends JFrame{
    public swing(){
        setTitle("root JFrame");
        getContentPane().setLayout(null);
        JButton jButton =  new JButton("Click Me to create a child JFreame");
        jButton.setBounds(200,300,150,150);
        getContentPane().add(jButton);
        JLabel jLabel = new JLabel("I'm nothing");
        jLabel.setBounds(150,170,100,100);
        getContentPane().add(jLabel);
        jButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                subswing sub = new subswing();
                sub.setVisible(true);
                getContentPane().add(sub);
                setVisible(false);//没有用
            }
        });
        pack();
    }
}
public class main {
    public static void main(String args[]){
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run(){
                    try {
                        swing s = new swing();
                        s.setVisible(true);
                        s.pack();
                    }catch (Exception e){
                        e.printStackTrace();
                    }
            }
        });
    }
}

异常

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: adding a window to a container
	at java.desktop/java.awt.Container.checkNotAWindow(Container.java:512)
	at java.desktop/java.awt.Container.addImpl(Container.java:1115)
	at java.desktop/java.awt.Container.add(Container.java:436)
	at main.swing$1.actionPerformed(main.java:31)
	at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
	at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
	at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
	at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
	at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
	at java.desktop/java.awt.Component.processMouseEvent(Component.java:6614)
	at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
	at java.desktop/java.awt.Component.processEvent(Component.java:6379)
	at java.desktop/java.awt.Container.processEvent(Container.java:2263)
	at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:4990)
	at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
	at java.desktop/java.awt.Component.dispatchEvent(Component.java:4822)
	at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4919)
	at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4548)
	at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4489)
	at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307)
	at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2769)
	at java.desktop/java.awt.Component.dispatchEvent(Component.java:4822)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
	at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
	at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)