Your code:

Take a look at the JRootPane-API, there is a method called "setJMenuBar".
Using this method, the RootPaneLayout (inner class of JRootPane) will handle
the correct sizing of the MenuBar. You should _not_ add the JMenuBar to the
contentPane.

Regarding your button-problem: You should add the button to a JPanel on
which you call setLayout(). If you do not care about resizing and centering
the button, you could call the method with null as parameter, which gives
you the freedom to resize/position elements via Component.setBounds(x, y,
width, heigth). Otherwise, the resizing of components  is being delegated to
the parent's LayoutManager.

Anyway, you should read carefully through the Layout-Api, as it may provide
you with the information you need. This should help, too:
http://java.sun.com/docs/books/tutorial/uiswing/layout/

HTH

Thorsten Suckow-Homberg

[...]

[...]
Menu bars are kind of special in Swing. You don't add a JMenuBar to the
contentPane like you do with all other components. Instead you use
JFrame's setJMenuBar(JMenuBar) method.

Not only about this. Did you try to think/read your self?
You cannot add JMenuBar to content pane, only by JFrame::setJMenuBar()
It means - you don't need to use any LayoutManager here.

Looking on your picture:
Both components (left and right) should have BorderLayout.
Left component:
- Your status (JLabel or JTextComponent) should occupate NORTH
- Your nested spilt pane should occupate CENTER
- Your button component (I think it should be JPanel with default
FlowLayout and JButton on it) should occupate SOUTH
Right component:
- Your JScrollPane with JList inside - CENTER (not NORTH!!!)
- Your button should occupate SOUTH (Looks like you want button to
occupate all available place)

example:
left/rightCompnent.add(what?, BorderLayout.CENTER);

Well, you are probably right.
Here is a course with several rather complex layout examples, including
sources:
http://java.sun.com/developer/onlineTraining/GUI/AWTLayoutMgr/shortcourse.html
(Actually I'm quite enthusiastic about this course. It must have been
drafted by a genius teacher)

<snip>

as mentioned a few times, it's just an understanding of how the different
layout managers work,
recognizing the default managers for various containers and
combining/nesting them to get the
desired effect (i.e. lots of trial and error)

You sound like you're trying to understand this, rather than after a
handout, so here's the code
from your other post, modified to include the buttons and menu.
(I find it easier posting the code and having you work it out, rather than
trying to explain it all)

import javax.swing.*;
import java.awt.*;
class Testing extends JFrame
{
 public Testing()
 {
   setSize(700,450);
   setDefaultCloseOperation(EXIT_ON_CLOSE);
   setLocation(300,100);
   JTextPane textAreaTop = new JTextPane();
   JScrollPane scrollTop = new JScrollPane(textAreaTop,22,31);
   JTextPane textAreaBottom = new JTextPane();
   JScrollPane scrollBottom = new JScrollPane(textAreaBottom,22,31);
   JSplitPane splitP = new
JSplitPane(JSplitPane.VERTICAL_SPLIT,scrollTop,scrollBottom);
   splitP.setResizeWeight(0.65);

   JPanel leftPanel = new JPanel(new BorderLayout());
   JButton btnSend = new JButton("Send");
   JPanel leftSouthPanel =new JPanel();
   leftSouthPanel.add(btnSend);
   leftPanel.add(splitP,BorderLayout.CENTER);
   leftPanel.add(leftSouthPanel,BorderLayout.SOUTH);

   JTextPane textAreaRight = new JTextPane();
   JScrollPane scrollRight = new JScrollPane(textAreaRight);
   JPanel rightPanel = new JPanel(new BorderLayout());
   JButton btnOnline = new JButton("Online");
   rightPanel.add(scrollRight,BorderLayout.CENTER);
   rightPanel.add(btnOnline,BorderLayout.SOUTH);

   JSplitPane splitP2 = new
JSplitPane(JSplitPane.HORIZONTAL_SPLIT,leftPanel,rightPanel);
   splitP2.setResizeWeight(0.85);
   getContentPane().add(splitP2);

   JMenu menuUser = new JMenu("User");
   JMenu menuMembers = new JMenu("Members");
   JMenu menuOwner = new JMenu("Owner");
   JMenuBar menuBar = new JMenuBar();
   menuBar.add(menuUser);
   menuBar.add(menuMembers);
   menuBar.add(menuOwner);
   setJMenuBar(menuBar);
 }
 public static void main( String args[] ){new Testing().setVisible(true);}
}