How to convert a date having ordinal format 1st March 1994?

问题

I want format a date given in the following format 1st March 1990. The date should be formatted to YYYY-MM-DD. I have the following code. It gives me an unparsable date. From this i can understand, this is not the correct way to format this date as its not a valid pattern.

public class DateFormattingTest {
    public static void main(String[] args) throws ParseException {
        String dateString = "1st March 1984";

        dateString = dateString.replaceFirst("[a-zA-Z]{2}","") ;
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("d MMMM yyyy");
        Date rightNow = simpleDateFormat.parse(dateString);
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
        String formattedDate = dateFormat.format(rightNow);
        System.out.println(formattedDate);
    }
}

I have revised and looked for date formatting patterns as well. I cannot find something related to this pattern "1st March 1990". I don't want sample code for this issue. I want to find out what am i doing wrong in here? Can someone suggest an approach to parse such a date?

Thanks.

回答1:

You have three problems.

First, you're trying to parse the date using the format YYYY-MM-DD. That's not the format of your data, which is why parsing is failing.
Second, you're expecting a Date object to retain information about a particular format. It doesn't. Instead, you would parse from one text format to a Date, and then use another DateFormat (with the desired output format) to format the Date into a String. Date.toString() will always use the same format, regardless of how you arrived at the Date.
Third, your format of YYYY-MM-DD isn't really what you want - you want yyyy-MM-dd. YYYY is the "weekyear", and DD is the "day of year".

I don't know of any SimpleDateFormat approach which would handle the ordinal part of your input string ("1st", "2nd" etc) - you'll probably need to put a bit of work into stripping that out. Once you've got a value such as "1 March 1990" you can parse with a SimpleDateFormat using the pattern d MMMM yyyy. Make sure you set the time zone and the locale appropriately.

回答2:

Your date 1st was not incorporated into the Java DateFormat. If you can switch to 1 and use the appropriate DateFormat, the parsing of Date will work or else you would need to convert the ordinal number to number by stripping the suffix. This might be a good related post to peek at.

回答3:

The problem is that your dateString does not match the pattern specified in your simpleDateFormat format. It is expecting a date in the format YYYY-MM-DD, the meaning of these symbols can be found here.

来源：https://stackoverflow.com/questions/26306797/how-to-convert-a-date-having-ordinal-format-1st-march-1994

标签

java

date-format