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How to stop JScrollPane from automatically updating the Scroll Bar value?

I use in my app a JscrollPane with a BoxLayout panel inside. I it to never change value after repainting. How can I do this?
I tried
pane.getHorizontalScrollBar().setValue()
but it doesn't change anything.

You could try setting the Horizontal (and/or) Vertical scrollbar policies:
pane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
pane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_NEVER);
You could also mess around with the Viewport's size (max & mins), etc.

Found solution.
Now I repaint panel inside scrollpane instead of scrollpane and it works.

need noRepaint() when i validate()

I have a JScrollPane with a View. I'm doing a chat application , it's why i need to have my ScrollBar to the Maximum(). To get the right Maximum of the View i have to validate before. When I validate my ScrollPane an automatic repaint is doing. I don't want this repaint because it makes a double repaint when i set the ScrollBar to the Maximum : when the ScrollBar is at the top and a another when it is a the bottom.
my code :
Main.getWindow().getMainPanel().getScrollPaneCenter().validate();
scrollPaneCenter.getVerticalScrollBar().setValue(scrollPaneCenter.getVerticalScrollBar().getMaximum());
PS : I want to disable the repaint of my conponent or maybe you have a solution to have a reversed JScrollPane( to always have the ScrollBar to Bottom) .

I'm doing a chat application
I'm guessing your are using a a JTextArea or JTextPane.
it's why i need to have my ScrollBar to the Maximum().
You don't need to validate or set the scrollbar manually. You juat append the text to the bottom of the Document. See Text Area Scrolling for a couple of solutions.

GWT: Draggable Popup with Scrollpanel

Designed a popup which is draggable, works as designed. Now Popup panel contains the ScrollPanel it is having vertical scroll bars, but while trying to scroll with dragging is not working

The following link gives u a window box implementation which is draggable. You can add scroll panel to it. I have tried it. It works. Have a look at it.
http://svn.clazzes.org/svn/gwt/branches/gwt-extras-0.1-branch/src/main/java/org/clazzes/gwt/extras/dialog/WindowBox.java

How to make JTextPane wrapped in JScrollPane shrink to fit the text

I have a JTextPane with HTML text.
I used GroupLayout (using WindowBuilder).
I've set the minimum size of my JFrame to 800x600 so the user cannot make it smaller than that.
The app has a big scrolling JPanel the size of the entire window. The top part of the panel is taken up by a JTextPane wrapped in JScrollPane. I have disabled the scroll bars and sized the JScrollPane to make the entire text visible.
In group layout the JScrollPane is set to stay constant vertically, but size horizontally.
My issue is that when the user makes the window larger the JScrollPane also expands, but now there is a big white space left at the bottom of the text pane. Is there a way that I can make JTextPane shrink to fit its contents.
Also if you suggest a different layout, I would be willing to try it.

I used this TextPanePerfectSize example from #camickr to solve a similar problem. The example uses validate() and pack() to adjust to the preferred size. You might be able to adapt it to your situation.

Take a look at SpringLayout. It gives you far more control over the positioning of components. Look at the SpringLayout tutorial if you get stuck.
The trick in your case is to bind the bottom (south) of your JScrollPane to the top (north) of the screen.

How do I limit vertical JDialog resizing to a single component within the dialog?

I have a JDialog that consists of two JPanels, one above the other. Currently, when I resize the JDialog only the bottom panel resizes in the vertical direction. However, I only want the top panel to resize. The only component that the top panel contains is a JScrollPane, so I want any vertical resizing to result in an increased/decreased view of the top panel's content. What is a good way to do this?
Thanks in advance!
elise

, I only want the top panel to resize
dialog.add(topPanel, BorderLayout.CENTER);
dialog.add(anotherPanel, BorderLayout.SOUTH);

This is a job for the proper LayoutManger. Here is a good link that explains LayoutManagers visually and does it quite well.