java - Why does SimpleDateFormat parse incorrect date?

Question

I have date in string format and I want to parse that into util date.

var date ="03/11/2013"

I am parsing this as :

new SimpleDateFormat("MM/dd/yyyy").parse(date)

But the strange thing is that, if I am passing "03-08-201309 hjhkjhk" or "03-88-2013" or 43-88-201378", it does not throw error , it parses it.

For this now, I have to write regex pattern for checking whetehr input of date is correct or not. but why is it so ??

Code :

scala> val date="03/88/201309 hjhkjhk"
date: java.lang.String = 03/88/201309 hjhkjhk

scala> new SimpleDateFormat("MM/dd/yyyy").parse(date)
res5: java.util.Date = Mon May 27 00:00:00 IST 201309

Answer 1

You should use DateFormat.setLenient(false):

SimpleDateFormat df = new SimpleDateFormat("MM/dd/yyyy");
df.setLenient(false);
df.parse("03/88/2013"); // Throws an exception

I'm not sure that will catch everything you want - I seem to remember that even with setLenient(false) it's more lenient than you might expect - but it should catch invalid month numbers for example.

I don't think it will catch trailing text, e.g. "03/01/2013 sjsjsj". You could potentially use the overload of parse which accepts a ParsePosition, then check the current parse index after parsing has completed:

ParsePosition position = new ParsePosition(0);
Date date = dateFormat.parse(text, position);
if (position.getIndex() != text.length()) {
    // Throw an exception or whatever else you want to do
}

You should also look at the Joda Time API which may well allow for a stricter interpretation - and is a generally cleaner date/time API anyway.