Specific date format from date string in java

Question

I have a date string which is

"20120514045300.0Z"

I'm trying to figure out how to convert this to the following format

"2012-05-14-T045300.0Z"

How do you suggest that I should solve it?

Answer 1

Instead of diving into hard-to-read string manipulation code, you should parse the date into a decent representation and from that representation format the output. If possible, I would recommend you to stick with some existing API.

Here's a solution based on SimpleDateFormat. (It hardcodes the 0Z part though.)

String input = "20120514045300.0Z";

DateFormat inputDF  = new SimpleDateFormat("yyyyMMddHHmmss'.0Z'");
DateFormat outputDF = new SimpleDateFormat("yyyy-MM-dd'-T'HHmmss.'0Z'");

Date date = inputDF.parse(input);
String output = outputDF.format(date);

System.out.println(output);  // Prints 2012-05-14-T045300.0Z as expected.

(Adapted from here: How to get Date part from given String?.)

Answer 2

You need to parse the date and them format it to desirable form. Use SimpleDateFormat to do it. You can also check out this question for more details.

Answer 3

You don't necessarily have to use a DateFormat for something as simple as this. You know what the format of the original date string is and you don't need a Date object, you want a String. So simply transform it directly into a String (without creating an intermediary Date object) as follows:

String s = "20120514045300.0Z";
String formatted = s.substring(0, 4) + '-' + s.substring(4, 6) + '-' + s.substring(6, 8) + "-T" + s.substring(8);

You can even use StringBuilder as follows (although this is a bit inefficient due to array copying):

StringBuilder sb = new StringBuilder(s);
sb.insert(4, '-').insert(7,'-').insert(10,"-T");
String formatted = sb.toString();

Answer 4

If you just need to reformat the string, you could use something like so:

String str = "20120514045300.0Z";
Pattern p = Pattern.compile("^(\\d{4})(\\d{2})(\\d{2})(.+)$");
Matcher m = p.matcher(str);
if (m.matches())
{
    String newStr = m.group(1) + "-" + m.group(2) + "-" + m.group(3) + "-T" + m.group(4);
    System.out.println(newStr);
}