java - Jscrollpane center aligns when label is too small

Question

This question is very similiar to this: JScrollPane doesn't top align when there is more than enough space to show the content I tried this solution, but it does not work.

When I add a jlabel to jscrollpane, when the jlabel is small, the label becomes centered. It works normally when the scrollbar shows. Setting boxlayout does not change anything. I feel like this isn't working properly because I'm setting a perferred size to the panel? But if I remove the line panel.setPreferredSize(new Dimension((int)(screenSize.width*0.7 - 50), screenSize.height-150)); The label becomes small when there is no text, and grows to accomdate text, which I don't want. If I add the panel instead of the label, it makes the screen scrollable even though there isn't text?

This is my code:

public class Test {
    // JFrame 
    static JFrame frame = new JFrame("Test"); 
    //panel 1
    static JPanel panel = new JPanel(new BorderLayout());
    // label to display text 
    static JLabel label = new JLabel(); 
    //scroll panel in main method
    
    
    public static void main(String[] args) throws Exception {
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();

        label.setBorder(new EmptyBorder(5, 5, 5, 20));
        label.setText("any text makes it centered beyond 40 lines");
        //create panel
        panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
        panel.add(label, BorderLayout.NORTH);
        panel.add(Box.createVerticalGlue());
        panel.setPreferredSize(new Dimension((int)(screenSize.width*0.7 - 50), screenSize.height-150));
        panel.setBorder(new EmptyBorder(5, 5, 5, 10));
        
        JScrollPane jspanel = new JScrollPane(label, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        //jspanel.add(label, BorderLayout.CENTER);
        jspanel.setPreferredSize(new Dimension((int)(screenSize.width*0.7 - 70), screenSize.height-180));
        jspanel.getVerticalScrollBar().setUnitIncrement(20);
        jspanel.setBorder(BorderFactory.createEmptyBorder());
        jspanel.setAlignmentX(JScrollPane.LEFT_ALIGNMENT);
        jspanel.setAlignmentY(JScrollPane.TOP_ALIGNMENT);
        //panel.setPreferredSize(new Dimension(640, 480));
        //frame.add(panel);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(jspanel);
        frame.setSize((int)(screenSize.width*0.7), screenSize.height - 50);
        frame.revalidate();
        frame.pack();  
        frame.setVisible(true);
    }
}

Answer 1

    jspanel.setAlignmentX(JScrollPane.LEFT_ALIGNMENT);
    jspanel.setAlignmentY(JScrollPane.TOP_ALIGNMENT);

That will align the scrollpane in its parent container, depending on the layout manager being used. It does not affect the alignment of any component added to the scrollpane. It is not needed.

the label becomes centered

The label is sized to fill the entire space available, so you need to customize how the text of the label is painted.

If you don't want it centered then you can place it at the top using:

label.setVerticalAlignment( SwingConstants.TOP );