Add JPanel to a JFrame

Question

I have two classes. One is the main frame, and the other class is a panel. The constructor of the main frame looks like this:
          JFrame.setDefaultLookAndFeelDecorated(true);
          JFrame frame = new JFrame("main");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          JPanel entryMgmt = new EntriesMgmt(dbConn);     
          frame.getContentPane().add(entryMgmt);
          frame.pack();
          frame.setVisible(true);The EntriesMgmt class extends JPanel. The constructor for it looks like this:
public EntriesMgmt(SqlBackend.DbConn conn){
          this.conn = conn;
          JPanel pane = new JPanel();
          //Add radio buttons
          pane.add(initRadioBtns());
          //Add input area
          pane.add(initInputArea());
          //Add buttons
          pane.add(initButtons());
     }The problem is that only the main window appears and there is nothing in it. I tried creating another JFrame in the EntriesMgmt constructor but it would cause 2 windows to appear and i don't want to use internalFrame because what I'm actually trying to do is have a JTabbedPane in the main window and I would have external JPanel under each tab. But let's concentrate on why is it that my EntriesMgmt panel does not appera in the main window.

Answer 1

What i did to fix this problem was the following. Since EntriesMgmt class extends JPanel I did not have to define another JPanel in the constructor but I could directly add components. Instead of :
public EntriesMgmt(){
JPanel pane = new JPanel();
          //Add radio buttons
          pane.add(initRadioBtns());
          //Add input area
          pane.add(initInputArea());
          //Add buttons
          pane.add(initButtons());I have:
public EntriesMgmt(){
          //Add radio buttons
          add(initRadioBtns());
          //Add input area
          add(initInputArea());
          //Add buttons
          add(initButtons());And somehow it works. Anyways I would like to know if there was any other way to do it.