问答题

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teachers。请将程序补充完整。public ChangeTitle(){super("Title Bar")；b1．addActionListener(this)；______Jpanel pane=new Jpanel()；Pane．add(b1)；Pane．add(b2)；SetContentPane(pane)；}public void actionPerformed(ActionEvent evt){Object sourve=evt．getSource()；if (sourve==b1)setTitle("Students")；else if (source==b2)setTitle("Teachers")；repaint()；}