CODEWITHSUNDEEP
javasimpledateformat
Ramesh
Ramesh

Reputation: 3881

Java SimpleDateFormat returns unexpected result

I'm trying to use SimpleDateFormat of Java to parse a String to date with the following code.

public class DateTester {

    public static void main(String[] args) throws ParseException {
        String dateString = "2011-02-28";

        SimpleDateFormat dateFormat = new SimpleDateFormat("MM-dd-yyyy");

        System.out.println(dateFormat.parse(dateString));
    }
}

I was expecting some parse error. But interestingly, it prints the following String.

Wed Jul 02 00:00:00 IST 195

Couldn't reason it out. Can anyone help?

Thanks

Upvotes: 15

Views: 1968

Answers (3)

Bohemian
Bohemian

Reputation: 425318

SimpleDateFormat has parsed 2011 as month number 2011, because month (MM) is the first part of the date pattern.

If you add 2011 months to year 28, you get year 195.

2011 months is 167 years and 7 months. July is the 7th month. You specified 02 as the day, 28 as the year, 28 + 167 = 195, so 02 July 195 is correct.

Upvotes: 22

Nathan Hughes
Nathan Hughes

Reputation: 96444

Call setLenient(false) on the dateFormat. Then you'll get your parse exception, like this:

groovy:000> df = new java.text.SimpleDateFormat("MM-dd-yyyy")
===> java.text.SimpleDateFormat@ac880840
groovy:000> df.setLenient(false)
===> null
groovy:000> df.parse("2011-02-28")
ERROR java.text.ParseException:
Unparseable date: "2011-02-28"
        at java_text_DateFormat$parse.call (Unknown Source)
        at groovysh_evaluate.run (groovysh_evaluate:2)
        ...

Bohemian is right, if you don't set the lenient property then the JDK will bend over backwards making sense of the garbage it's given:

groovy:000> df = new java.text.SimpleDateFormat("MM-dd-yyyy");
===> java.text.SimpleDateFormat@ac880840
groovy:000> df.parse("13-01-2011")
===> Sun Jan 01 00:00:00 CST 2012
groovy:000> df.setLenient(false)
===> null
groovy:000> df.parse("13-01-2011")
ERROR java.text.ParseException:
Unparseable date: "13-01-2011"
        at java_text_DateFormat$parse.call (Unknown Source)
        at groovysh_evaluate.run (groovysh_evaluate:2)
        ...

Upvotes: 5

tim_yates
tim_yates

Reputation: 171154

By default, SimpleDateFormat is lenient, so to get it to fail, you need to do:

dateFormat.setLenient( false ) ;

before parsing the date. You will then get the exception:

java.text.ParseException: Unparseable date: "2011-02-28"

Upvotes: 23

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