java学习：日期的运算代码

importjava.text.SimpleDateFormat;
importjava.util.Calendar;
importjava.util.Date;

publicclassHelloWorld{

   publicstaticvoidmain(String[]args){

       //指定时间输出格式
       SimpleDateFormatsdf=newSimpleDateFormat("yyyy-MM-ddhh:mm:ss");

       Datedt=newDate();
       System.out.println("当前时间："+sdf.format(dt));

       CalendarrightNow=Calendar.getInstance();
       rightNow.setTime(dt);        

       rightNow.add(Calendar.YEAR,-1);//当时日期减1年
       System.out.println("减1年："+sdf.format(rightNow.getTime()));

       rightNow.add(Calendar.MONTH,3);//(在刚才的结果上)再加3个月
       System.out.println("再加3个月："+sdf.format(rightNow.getTime()));

       rightNow.add(Calendar.DAY_OF_YEAR,10);//(在刚才的结果上)再加10天        
       System.out.println("再加10天："+sdf.format(rightNow.getTime()));

 
   }
}