Their are a variety of strategies, depending on the
minimum Java version your software requires.

You might..
- serialise the GUI (relatively inefficient, and
problematic when the app. changes)
<http://java.sun.com/j2se/1.5.0/docs/api/java/io/Serializable.html>
- store the important details as properties.
<http://java.sun.com/j2se/1.5.0/docs/api/java/util/Properties.html>
- create a Java bean to represent the important information
   and write it to disk as XML ('insert XML should not be
   used for this' argument here)
<http://java.sun.com/j2se/1.5.0/docs/api/java/beans/XMLEncoder.html>
<http://java.sun.com/j2se/1.5.0/docs/api/java/beans/XMLDecoder.html>

The best way would probably be the second.

The users can only tweak so many things that affect layout, often just
the location and size of the total frame.  If you persist that,
everything else will more or less come out in the wash.

The outside frame can be reconstituted with setLocation setSize set
Bounds.

JSplitPane can be persisted with getDividerLocation
setDividerLocation.

the position of a JScrollPane could be persisted with
getHorizontalScrollBar().getValue()

The Preferences mechanism is great for this task:

here is how you would persist a JFileChooser state:

// ask user where to save.
// persisted in registry directory last used

Preferences userPrefs = Preferences.userRoot().node(
"/com/mindprod/mypackage" );

File suggestedFile = new File ( userPrefs.get( "SAVEDIR", "C:" ),
saveName );
...
     // save same directory for next time.
     // persisted in registry, directory last used
     userPrefs.put( "SAVEDIR",
fc.getCurrentDirectory().getAbsolutePath() );

Thanks for your help, Mr Thompson and Mr Green(Or should I call you guys
Andrew and Roedy instead? You know, I often get
confused by  my Chinese-English).
I know the way about how to store the properties,  using property file or
xml file. But the problem is , how can I get the "properties"? There are 2
pictures in my msn-space:
http://spaces.msn.com/members/xingyukun1981
Their names are "Eclipse1" and "Eclipse2", in the view "technology" of my
album.
Let's presume Eclipse1 is the initial state, and after the user do some
dragging, the view comes to "Eclipse2". At this time ,we close Eclipse, then
open it again----yes, the perspective in front of us is "Eclpse2".
So how could that be done? Do I have to get the sizes of all the components
in the perspective?