java常用日期代码

//输出今天开始的日期和星期
void printWeek() throws Exception{
        SimpleDateFormat dfDay = new SimpleDateFormat("yyyy-MM-dd");
        String today = dfDay.format(new Date());

        //String[] weekDays = {"星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六"};
        String[] weekDays = {"日", "一", "二", "三", "四", "五", "六"};
        Calendar calendar   =   new GregorianCalendar();
        calendar.setTime(dfDay.parse(today));
        for(int i=0;i<7;i++){
            if(i==0){
                calendar.add(calendar.DATE, 0);
            }else {
                calendar.add(calendar.DATE, 1);//把日期往后增加一天.整数往后推,负数往前移动
            }
            String hkrq = dfDay.format(calendar.getTime());//格式要 yyyy-MM-dd
            int w = calendar.get(Calendar.DAY_OF_WEEK) - 1;
            if (w < 0)
                w = 0;

            System.out.println(hkrq+" "+weekDays[w]);
        }
    }