Java Swing - 如何在一个小框架内显示JList的滚动条

import java.awt.BorderLayout;

import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;

public class Main {
  public static void main(String[] args) {
    JFrame frame = new JFrame();
    JPanel panel = new JPanel();
    JScrollPane listScrollPane = new JScrollPane();
    String[] stringArray = { "Testing", "This", "Stuff" };
    JList<String> rowList = new JList<>(stringArray);

    rowList.setVisibleRowCount(2);
    listScrollPane.setViewportView(rowList);
    panel.setLayout(new BorderLayout());
    panel.add(listScrollPane);
    frame.add(panel);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    frame.pack();
    frame.setVisible(true);

  }
}