填空题

本题中定义了一个树型的通信录，窗口左侧是一个树，右侧是一个文本域，单击树的结点，则在右侧文本域中显示相关信息，如果单击的是树结点，则显示对应名字的电话信息。
import javax. swing. * ;
import javax. swing. tree. * ;
import java. awt. * ;
import java. awt. event. * ;
import javax. swing. event. * ;
class Mytree2 extends JFrame______
JTree tree=null; JTextArea text=new JTextArea(20,20);
Mytree2()
Container con=getContentPane();
DefauhMutableTreeNode root=new DefauhMutableTreeNode ("同学通信录");
DefaultMutableTreeNode t1=new DefauhMutableTreeNode("大学同学");
DefaultMutableTreeNode t2=new DefaultMutableTreeNode("研究生同学");
DefaultMutableTreeNode t1_1=new DefauhMutableTreeNode("陈艳");
DefauhMutableTreeNode t1_2=new DefaultMutableTreeNode("李小永");
DefauhMutableTreeNode t2_1=new DefaultMutableTreeNode("王小小");
DefaultMutableTreeNode t2_2=new DefaultMutableTreeNode("董小");
setTitle("java2");
root. add(t1); root. add(t2);
t1. add(t1_1); t1, add(t1_2); t2. add(t2_1); t2. add(t2_2);
tree=new JTree(root);
JScrollPane scrollpane=new JScrollPane(text);
JSplitPane splitpane=new JSplitPane(JSplitPane. HORIZONTAL_SPLIT,
true, tree, scrollpane);
tree. addTreeSelectionListener(this);
con. add(splitpane);
addWindowListener( new WindowAdapter()
public void windowClosing(WindowEvent e)
System. exit(0););
setVisible(true); setBounds(70,80,200,300);

public void valueChanged(TreeSelectionEvent e)
if(e, getSource()==tree)
DefaultMutableTreeNode node=
(DefaultMutableTreeNode) tree. getLastSelectedPathComponent();
if(node. isLeaf())
String str=______;
if(str. equals("陈艳"))
text. setText(str+":联系电话: 0411-4209876");
else if(str. equals("李小永"))
text. setText (str+":联系电话: 010 -62789876");
else if(str. equals("王小小"))
text. setText (str+": 联系电话: 0430-63596677");
else if(str. equals("董小"))
text. setText(str +": 联系电话: 020-85192789");

else
text. setText(node. getUserObject(). toString());




public class java2
public static void main(String args[])
Mytree2 win=new Mytree2(); win. pack();