为什么我的JList / JScrollPane这么小？

Question

当我运行我的代码时，JList显示但它确实很小，当我尝试改变它的大小时，它不会改变大小。我做错了什么？很多GUI格式对我来说都是新的。感谢。

public class Panel extends JPanel
{
//Fields
private Dimension dimensions; 
private JButton button1; 
private JList list; 
private JScrollPane listScroller; 
private String title;
private DefaultListModel model; 

/**
 * Constructor 
 */

public Panel()
{
    dimensions = new Dimension(400, 300);
    setPreferredSize(dimensions);
    setBackground(Color.WHITE);
    setLayout(null); //Lets me lay my components out freely 

    button1 = new JButton("New Set"); 
    button1.setBounds(new Rectangle(new Point(150, 250), button1.getPreferredSize()));
    button1.addActionListener(new ButtonListener());
    add(button1);

    String[] titleArray ={title};
    model = new DefaultListModel(); 
    for(String title :titleArray)
    {
        model.addElement(title); 
    }
    list = new JList(model);
    list.setBounds(new Rectangle(new Point(200,200), list.getPreferredSize()));
    add(list);

    listScroller = new JScrollPane(list);
    listScroller.setBounds(new Rectangle(new Point(200,200), listScroller.getPreferredSize()));
    add(listScroller);
}
}