SimpleDateFormat.parse（） - 为不同的日期格式生成错误的日期

Question

Below is my code to parse the date using SimpleDateFormat with pattern:

String pattern = "yyyy-MM-dd";    
SimpleDateFormat format = new SimpleDateFormat(pattern);
try {
    Date date = format.parse("05-21-2030");
    System.out.println(date);
} catch (ParseException e) {
    e.printStackTrace();
}

You can see the date which I passed to parse is different from date format which is specified in SimpleDateFormat. In this case I was expecting kind of excpetion as format is different but it parsed successfully with some different date values. I got the output - Tue Mar 22 00:00:00 IST 12

When I pass the same format like 2030-05-21 it works fine.

Can you guys please let me know how can I prevent such things in my code?

Answer 1

Basically you want SimpleDateFormat to be strict, so set lenient to false.

SimpleDateFormat format = new SimpleDateFormat(pattern);
format.setLenient(false);

Answer 2

If you can afford using Java 8 time API, its formatter works as expected:

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
try {
    LocalDate date = LocalDate.parse("2030-05-21", formatter);
    System.out.println(date);
    LocalDate date2 = LocalDate.parse("05-21-2030", formatter);
    System.out.println(date2);
} catch (DateTimeParseException e) {
    e.printStackTrace();
}

Output:

2030-05-21
java.time.format.DateTimeParseException: Text '05-21-2030' could not be parsed at index 0
    at java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:1947)
    at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1849)
    at java.time.LocalDate.parse(LocalDate.java:400)
    at java8.Snippet.main(Snippet.java:25)