You can find many tips on how to center a window within the screen, but howabout centering a window in its parent container? The following code showsyou how to do that. Say you have a JFrame (or Frame), and you launch a JDialog (or Dialog) likethis:

 JDialog jd = new JDialog(this); //you have to pass the this pointer of Frame to establish//parent-child (or owner-owned) relationshipjd.setVisible(true);

In the code for jd you can have the following to center the dialog withrespect to its ownere frame:

 public void centerInParent () {    int x;    int y;    Container parent = this.getParent();    Point topLeft = parent.getLocationOnScreen();    Dimension parentSize = parent.getSize();    Dimension ownSize = this.getSize();    if (parentSize.width < ownSize.width)         {x = ((parentSize.width - ownSize.width)/2) +
 topLeft.x;}   else         {x = topLeft.x;}   if (parentSize.height < ownSize.height)        {y = ((parentSize.height - ownSize.height)/2) + 
topLeft.y;}   else        {y = topLeft.y;}    this.setLocation (x, y);    this.requestFocus();}  

For the sake of completeness, the following code centers a Dialog or Framewithin the screen:

 public void centerInScreen() {    Dimension dim = this.getToolkit().getScreenSize();    Rectangle bounds = this.getBounds();    this.setLocation((dim.width - bounds.width) / 2, 
(dim.height -bounds.height) / 2);    this.requestFocus();}