Java 得到某一日期的前一天 后一天 并得到该三天分别是星期几

public static void main(String[] s) throws ParseException{
  
  String day = "2014-08-01";
  
  String beforeWeek = "";
  String dayWeek = "";
  String afterWeek = "";
  String[] weekDatas = {"星期日","星期一","星期二","星期三","星期四","星期五","星期六"};
  
  String beforeDay = ""; //前一天
  //根据当前日期得到前一天的日期
  SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
  Date dd = format.parse(day);
  Calendar calendar1 = Calendar.getInstance();
  calendar1.setTime(dd);
  int week_index = calendar1.get(Calendar.DAY_OF_WEEK) - 1; 
        if(week_index<0){ 
            week_index = 0; 
        }  
        dayWeek = weekDatas[week_index];
  calendar1.add(Calendar.DATE,-1);
  week_index = calendar1.get(Calendar.DAY_OF_WEEK) - 1; 
        if(week_index<0){ 
            week_index = 0; 
        }
        beforeWeek = weekDatas[week_index];
  beforeDay = format.format(calendar1.getTime()) ;
  
  String afterDay = ""; //后一天
  //根据当前日期得到后一天的日期
  dd = format.parse(day);
  Calendar calendar2 = Calendar.getInstance();
  calendar2.setTime(dd);
  calendar2.add(Calendar.DATE,1);
  week_index = calendar2.get(Calendar.DAY_OF_WEEK) - 1; 
        if(week_index<0){ 
            week_index = 0; 
        }
        afterWeek = weekDatas[week_index];
  afterDay = format.format(calendar2.getTime()) ;
  
  System.out.println(beforeDay+beforeWeek);
  System.out.println(day+dayWeek);
  System.out.println(afterDay+afterWeek);
  
 }