转自：http://blog.sina.com.cn/s/blog_a2614218010188lb.html

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);

 

    }

 

}

 

注：在Calendar对象的add方法中，第二个参数为正数表示“加”，负数表示“减”

 

 

获取系统当前时间（String类型）

public static String getStringDateShort() {

     Date currentTime = new Date();

     SimpleDateFormat formatter = new SimpleDateFormat("yyyyMMdd");

     String dateString = formatter.format(currentTime);

     return dateString;

    }