问答题 下面是实现用户界面程序的一个例子，请在画线处填写适当语句，使程序能正确执行。 import java.awt.*; import java.awt.event.*; public class AWTExample6 extends MouseAdapter{ private Frame frame; private TextArea textArea; private MenuItem about; private MenuItem exit; private PopupMenu popupMenu; private Panel panel; public void initGUI(){ flame=new Frame("mouse event")； textArea=new TextArea(" ",10,10); ______ frame.add(textArea); frame.setSize(200,200); frame.setVisible(true); frame.addWindowListener(new WindowAdapter(){ public void windowClosing(WindowEvent e){ System.exit(0);} }); } public void mousePressed(MouseEvent event){ if(event.getModifiers()==event.BUTTON1_MASK){ textArea.append("点击左键"+"/r/n"): textArea.append("点击位置:x="+event.getX()+" y="+event.getY()+"/r/n"); textArea.append("点击次数"+event.getClickCount()+"/r/n"); } else if(event.getModifiers()==event.BUTTON3_MASK){ textArea.append("点击右键"+"/r/n"); textArea.append("点击位置:x="+event.getX()+" y="+event.getY()+"/r/n"); textArea.append("点击次数"+event.getClickCount()+"/r/n"); } } public static void main(String args[]){ AWTExample6 example=new AWTExample6(); example.initGUI(); } }