Java SE (Java Platform, Standard Edition)

I am having this problem with the JScrollPane where the scroll bar positions itself in the center, and not at the top and I can't figure out why.
Here is a code snippet:

JPanel userProfilePanel= new JPanel();
               userProfilePanel.setSize(new Dimension(600,800));
		userProfilePanel.setPreferredSize(new Dimension(600,800));
		
		JScrollPane  userProfileScrollPane=new JScrollPane(userProfilePanel, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
		userProfileScrollPane.setSize(new Dimension(600,600));
		
		
		JTabbedPane tabbedPane=new JTabbedPane(); 
		tabbedPane.setSize(new Dimension(600,600));
		tabbedPane.addTab("Profile", null, userProfileScrollPane,"Does nothing");
 
               JDialog screen=new JDialog();
                screen.getContentPane().add(tabbedPane);
		userProfileScrollPane.getHorizontalScrollBar().setValue(0);
		userProfileScrollPane.getVerticalScrollBar().setValue(0);
		
		
		screen.repaint();
screen.setVisible(true);

Does anyone have an idea what it is doing this?