出现错误找不到符号 怎么解决？求高手指点

class Timestamp{
          int hrs;
          int mins;
          int secs;
        void fillTime(){
              java.util.Calendar now;
              now=java.util.Calendar.getInstance();
              hrs=now.get(java.util.Calendar.HOUR_OF_DAY);
              mins=now.get(java.util.Calendar.MINUTE);
              secs=now.get(java.util.Calendar.SECOND);
                       }
                }
public class clock{
         public static void main (String [] args){
                      ClockView cv;
                      cv=new ClockView();
                      cv.setVisible(ture);
                      //loop about every 0.5 seconds
                     try{
                         for(;;){
                         cv.refeshTimeDisply();
                         Thread.sleep(500);
                                }
                         }catch (Exception e) {System.out.println("Error:"+e);}
                                                   }
                  }
class ClockView extends javax.swing.JFrame{
     private javax.swing.JLabel tLabel = new javax.swing.JLabel();
  void   clockView(){//constructor
          this.setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
          this.setSize(95,45);
          this.getContentPane().add(tLabel);
          this.refreshTimeDisplay();
                 }
    protected String getDigitsAsString(int i){
              String str=Integer.toString(i);
              if(i<10) str="0"+str;
              return str;
         } 
    public void refreshTimeDisplay(){
       Timestamp t= new Timestamp();
       t.fillTimes();
       String disply = getDigitsAsString(t.hrs)+":"+ getDigitsAsString(t.mins)+":"+ getDigitsAsString(t.secs);
       tLabel.setText(" "+display);
       tLabel.repaint();
       }
}
               
                    --------------------编程问答-------------------- 你至少得把出现错误的行号发上来啊。

补充：Java ,  Java EE