//panel1中加了个textArea 
JTextArea tArea=new JTextArea(15,20); 
tArea.setBorder(new LineBorder(Color.blue)); 
pn1.add(tArea); //panel1的下部加了个panel2 
JPanel pn2=new JPanel(true); 
pn1.add("South",pn2); //panel2中添加个button 点这个button清空上面的textArea 
JButton btn2=new JButton("Cancel"); 
btn2.addActionListener( 
                          new ActionListener(){ 
                                                public void actionPerformed(ActionEvent event){ 
                                                    tArea.setText(""); 
                                                  } 
                                              } 
                            ); 
pn2.add(btn2); 编译器说找不到tArea