年份不是四位数时的日期解析异常

Question

I have the following code in Java.

SimpleDateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy");
String expiryDateInString = "05/14/86";

final Instant expiryDate = dateFormat.parse((expiryDateInString)).toInstant();

I want this to cause a parse exception but i am getting a year parsed as 0086, which i believe is way in the past. How can i make the year to be a strictly 4 digit year and anything else will give an exception.

Answer 1

Using java.time instead of the previous date API, you can use DateTimeFormatter that will throw an exception if it is not a correct year

DateTimeFormatter.ofPattern("MM/dd/uuuu").parse(("05/14/86")

Exception in thread "main" java.time.format.DateTimeParseException: Text '05/14/86' could not be parsed at index 6

DateTimeFormatter.ofPattern("MM/dd/uuuu").parse(("05/14/1986")

1986-05-14

In the opposite case, if you want to allow both 2 and 4 digit year, you can use the "optional" feature of the formatter using [ and ] . Providing both possible format for the year uuuu and uu in optional blocks, you will have :

DateTimeFormatter.ofPattern("MM/dd/[uuuu][uu]").parse(("05/14/86")

2086-05-14

DateTimeFormatter.ofPattern("MM/dd/[uuuu][uu]").parse(("05/14/1986")

1986-05-14