如何使JScrollPane从头开始？

Question

我正在尝试让JScroll从顶部开始，但是它总是从结尾开始。我在互联网上发现了这么多解决方案，但对我不起作用。谁能在这段代码中告诉我问题？

这是课程：

public class BuildPanel extends JPanel{

    GameSideCore gsc;
    JPanel panel;
    JScrollPane spane;
    ArrayList<BuildPanelL> newPanels = new ArrayList<>();

    public BuildPanel(GameSideCore gsc){
        this.gsc = gsc;
        setSize(640,240);
        setBackground(Color.blue);
        setLayout(null);
        panel = new JPanel();
        panel.setPreferredSize(new Dimension(600, 0));
        panel.setLayout(null);
        spane = new JScrollPane(panel);
        spane.setPreferredSize(new Dimension(getWidth(),getHeight()));
        spane.setBounds(0, 0, 640, 240);
        spane.getVerticalScrollBar().setUnitIncrement(12);
        JScrollBar jsBar = spane.getVerticalScrollBar();
        jsBar.setValue(spane.getVerticalScrollBar().getMinimum());
        spane.setVerticalScrollBar(jsBar);
        add(spane);

    }

    public void BPanel(){
        panel.removeAll();
        System.out.println("BPanel");
        for(int i = 1; i < 30; i++){
            for(int m = 0; m < 30; m++){
                if( gsc.location[m] == i){
                    newPanels.add(new BuildPanelL(i));
                    break;
                }
            }
        }
        panel.setPreferredSize(new Dimension(600, newPanels.size()*121));
        for(int i = 0; i < newPanels.size(); i++){
            panel.add(newPanels.get(i));
            newPanels.get(i).setBounds(0, 0+i*121, 600, 120);
            System.out.println("This is ."+i);
        }
        repaint();
    }   

}