计算3天的日期

1.获取当前的年份

SimpleDateFormat df = new SimpleDateFormat("yyyy");
String year = df.format(new Date());

2.获取前3天的日期

Calendar calendar = Calendar.getInstance();
Date date = new Date(System.currentTimeMillis());
calendar.setTime(date);
calendar.add(Calendar.DATE, -3);
date = calendar.getTime();
System.out.println("   '"+new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(date)+"  ");