Java对日期Date类进行加减运算，年份加减，月份加减

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class DateTestUtil {

   
    public static void main(String[] args) throws Exception {
       
        SimpleDateFormat sdf=new SimpleDateFormat("yyyyMMdd");
        String str="20110823";
        Date dt=sdf.parse(str);
        Calendar rightNow = Calendar.getInstance();
        rightNow.setTime(dt);
        rightNow.add(Calendar.YEAR,-1);//日期减1年
        rightNow.add(Calendar.MONTH,3);//日期加3个月
        rightNow.add(Calendar.DAY_OF_YEAR,10);//日期加10天
        Date dt1=rightNow.getTime();
        String reStr = sdf.format(dt1);
        System.out.println(reStr);

    }

}