如何在JPanel中动态添加JButton ?

In NetBeans, I have used the GUI editor to make a JFrame and I've put a JPanel in the frame. At the moment, I'm trying to make a new button in the panel when the class constructs. This is the code I have, but I can't seem to get it to work. (The first line makes the button, the other lines try to show it.)In NetBeans, I have used the GUI editor to make