问答题

本程序监听列表选择的操作和关闭窗口的操作。当选中列表中的某个选项时，产生一个随机数做为选中对象的ID，然后显示于窗口下方的文本框中，当单击“关闭窗口”按钮时关闭窗口退出程序，如图所示。


import java.awt.*;
import java.awt.event.*;
import java.util.*;
public class exam_62 implements______, WindowListener
{
private Frame f;
private java.awt. List ist;
private TextField tf;
static Random num=new Random(1000);
public void create () {
f=new Frame ( "exam_62" );
tf=new TextField();
lst=new java.awt. List(4, false);
lst.add("Hao JianWen");
lst.add("Gu ZhiFeng");
lst.add("Zou Tao");
lst. add ( "Ma Lu" );
lst. addItemListener (this);
f.add (ist, "Center");
f.add (tf,"South");
______;
f.setSize(300,200);
f. setVisible (true);
}
public void itemStateChanged (ItemEvent e) {
int id= ( (java.awt. List) e.getSource ()) .getSelectedIndex ();
switch (id) {
case 0:{ tf.setText("Hao JianWen"s ID is: "+ num.nextInt());
break;
}
case 1:{tf.setText("Gu ZhiFeng"s ID is: "+num.nextInt());
break;
}
case 2:{tf.setText("Zou Tao"s ID is: "+num.nextInt());
break;
}
case 3:{tf.setText("Ma Lu"s ID is: "+num.nextInt());
break;
}
}
}
public void windowClosing(WindowEvent e) {
System.exit (1);
}
public void windowOpened (WindowEvent e) { }
public void windowIconified (WindowEvent e) { }
public void windowDeiconified(WindowEvent e) { }
public void windowClosed (WindowEvent e) { }
public void windowActivated(WindowEvent e) { }
public void windowDeactivated(WindowEvent e) { }
public static void main(String args[])
{
exam_62 ml=new exam_62 ();
ml. create (); }
}