3天前：取负值
Calendar calendar1 = Calendar.getInstance();
SimpleDateFormat sdf1 = new SimpleDateFormat(“yyyyMMdd”);
calendar1.add(Calendar.DATE, -3);
String three_days_ago = sdf1.format(calendar1.getTime());
System.out.println(three_days_ago);
同理，3天后，取正值即可：
Calendar calendar2 = Calendar.getInstance();
SimpleDateFormat sdf2 = new SimpleDateFormat(“yyyyMMdd”);
calendar2.add(Calendar.DATE, 3);
String three_days_after = sdf2.format(calendar2.getTime());
System.out.println(three_days_after);
原创文章，作者：ItWorker，如若转载，请注明出处：https://blog.ytso.com/tech/pnotes/17469.html