How Java2D repaint( ) works?

Question

Never mind my problem with not drawing lines. Found the error myself. But it is still greatly appreciated if you could explain how repaint( ) works.
<< Edit ends >>
Old post:
I am very new to Java2D. I am programing an application that need GUI and 2D and got curious about how a panel with '2D' image updates the content.
The program has GUI interface with all menu and buttons, displaying an empty 'content' panel in the middle at the start. Information will be read in from a file and the program should display series of boxes like this:
|    |        |     |             | |        |         |
and another one
|           | |      |           |  |              |   |
--------------------------------------------------------Then, a button named 'align' will match the box stretches between two neighboring series, and the program suppose to display like this:
|    |        |     |             | |        |         |
                    |                        |
|______________________|_______________________________
|             | |      |           |  |           |   |
--------------------------------------------------------pseudo code for related components is like this:
public class alignbox {
  private Boxes[ ]boxes; // store information of box series
  private Alignment aln; // store informations of alignment
  private jFrame frame;
  private jButton[ ] quite_a_few_buttons;
  private DrawPanel pane = new DrawPanel( );
  ... // after button is clicked
  frame.getContentPane( ).repaint( );
  // "content panel"
  private class DrawPanel {
   public DrawPanel( ) {
     init( );
   void init( ) {
      Shape[ ] boxShapes = new Shape[ numOfSeries ];
      for (each bs of boxShapes)
         bs = getPath (boxes);
     Shape[ ] alignedLines = new Shape [numOfSeries -1];
      for (each line of alignedLines)
          line = getPath (aln);
  void paintComponent(Graphics g){
        init( );
        // draw boxes after "open" file
        // daw boxes and alignment lines after "align" button pressed
}from what I read, paintComponent(Graphics g) is the main play displaying images I want. I can get boxes display fine, but I couldn't get alignment line displayed at all.
Does repaint( ) call paintComponent( ) at all? I include 'init( )' in the paintComponent( ). will it allow the updates of boxes[ ] and aln reflected in the DrawPanel?
if not, how do I 'tell' DrawPanel that boxes infor or alignment info has been updated and redisplay the content? Should there be a better way to do so unlike my clumsy method?
Thanks!

Answer 1

Swing related questions should be posted in the Swing forum.
The repaint() invokes the paint() method which in turn ivokes the paintComponent() method (among others). Read the Swing tutorial on [url http://java.sun.com/docs/books/tutorial/uiswing/14painting/index.html]Painting for more information.