[填空题] 下面ChangeTitle()中对b1和b2按钮构造监听器，实现当单击b1按钮时标题变为students，当单击b2按钮时标题变为teachen。请

[填空题] 下面ChangeTitle()中对b1和b2按钮构造监听器，实现当单击b1按钮时标题变为students，当单击b2按钮时标题变为teachen。请将程序补充完整。

public ChangeTitle()

super("Title Bar");

b1. addActionListener(this); 【15】

Jpanel pane = new Jpanel();

Pane.add(b1);

Pane.add(b2);

SetContentPane(pane);public void actionPefformed(ActionEvent evt)

Object sourve = evt. getSource();

if (sourve ==b1)

setTitle("Students");

else if (source == b2)

setTitle("Teachers ");

repaint();

b2.addAcfionListener(this)；