Java - go to JFrame or JPanel

dispose();  //System.exit(0);

// open new window (JParent = JFrame)
new JParent().setVisible(true);

// close parent window and open child window
//JFrame frame = new JFrame();   // extends JFrame
super.setContentPane(new JChild());  // JChild = JPanel
//super.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);    // exit
super.pack();
super.setVisible(true);