Java Swing - 如何获取第一个可见项的索引

import javax.swing.JList;

public class Main {
  public static void main(String[] argv) throws Exception {
    String[] items = { "A", "B", "C", "D" };
    JList list = new JList(items);

    int itemIx = list.getFirstVisibleIndex();
    if (itemIx < 0) {
      // List is either not visible or there are no items
    }
  }
}