获取某周前的礼拜一详解编程语言

package com.poi.examples;   
   
import java.text.SimpleDateFormat;   
import java.util.*;   
   
public class PrevWeek {   
     public static void main(String[] args) {   
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");   
            Date dt = prevWeek(new Date(), 7);   
            System.out.println(sdf.format(dt));   
        }   
        
        public static Date prevWeek(Date dt, int week) {   
            Calendar cal = Calendar.getInstance();   
            cal.setTime(dt);   
            cal.add(Calendar.DAY_OF_MONTH, -week * 7 + (9-cal.get(Calendar.DAY_OF_WEEK)));   
            return cal.getTime();   
        }   
}