JAVA高级01_08 与日期和时间有关的类 2011-4-21

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与日期和时间有关的类
最常用几个类:Date、DateFormat和Calendar
Calendar类
-Calendar.add方法
-Calendar.get方法，获取年月日时间值
-Calendar.set方法
-Calendar.getInstance静态方法
-GregorianCalendar子类
Date类
java.text.DateFormat与java.text.SimpleDateFormat子类

Calendar cl = Calendar.getInstance();
System.out.println(cl.get(Calendar.YEAR) + "年" + cl.get(Calendar.MONTH) + "月" +
                     cl.get(Calendar.DAY_OF_MONTH) + "日" + cl.get(Calendar.HOUR) + ":" +
       cl.get(Calendar.MINUTE) + ":" + cl.get(Calendar.SECOND) );
   cl.add(cl.DAY_OF_YEAR,315);//315天后的日期
   System.out.println(cl.get(Calendar.YEAR) + "年" + cl.get(Calendar.MONTH) + "月" +
                     cl.get(Calendar.DAY_OF_MONTH) + "日" + cl.get(Calendar.HOUR) + ":" +
       cl.get(Calendar.MINUTE) + ":" + cl.get(Calendar.SECOND) );
    SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd");
    SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy年MM月dd日");
    try
    {
      Date d = sdf1.parse("2003-03-15");
      System.out.println( sdf2.format(d) );
    }
    catch(Exception e)
    {
      e.printStackTrace();
    }
class MyTimerTask Extends TimerTask
{
    private Timer tm = null;
    public MyTimerTask(Timer tm)
    {
     this.tm = tm
    }
    public void run()
    {
     try
      {
        Runtime.getRuntime().exec("calc.exe");
      }
      catch(Exception e)
      {
        e.printStackTrace();
      }
      //结束任务线程的代码
      tm.cancel();
      //this.cancel();
    }
}

Timer tm = new Timer();
tm.schedule( new MyTimerTask(tm),30000);

Timer与TimerTask类
schedule方法主要有如下几种重载形式
schedule(TimerTask task,long delay);
schedule(TimerTask task,Date time);
schedule(TimerTask task,long delay,long period);
schedule(TimerTask task,Date firstTime,long period);
TimerTask类实现了Runnable接口，要执行的任务由它里面实现的
run方法来完成。