How to remove all components from a JFrame in Java?

Question

I'm writing a program where I have a JFrame and I want to remove all components from it, then add just one component to it and repaint the frame. What I have so far is something like the code below (called in an object that implements JFrame, where StartPanel implements JPanel):

removeAll();    
startPanel = new StartPanel();
startPanel.setVisible(true);
add(startPanel);
revalidate();
repaint();

However, when I run the code it shows an empty window (not the startPanel) and when I minimize/resize the window, the window turns black. If I leave out the removeAll() and there are not elements already on the JFrame it displays the startPanel just fine. Any ideas on how to actually remove everything, and then get the new panel to still show up?

Answer 1

You must call

 private JFrame frame = new JFrame();
 ...
 ...
 frame.getContentPane().removeAll();
 frame.repaint();

removeAll() has not been overridden as add() or remove() to forward to the contentPane as necessary.

Answer 2

getContentPane().removeAll();
getContentPane().repaint();

Answer 3

assuming your goal is to add something else after you clear the frame you should call validate after adding thoes components to update it

getContentPane().removeAll();
add(new component);
validate();