Format String with pattern

Question

Hi Folks,
my Problem is that i need to format a String by using a pattern.
The Input String is like "20081208" and the Output String has to be "2008-12-08".
I could simply do this by using String.substring but i think it's not that elegant.
Also i found a way by doing it with SimpleDateFormat.
But it needs to much lines of code to do this as it's worth.
Is there a simple way like String.format just to do this in one line?
I'd like to pass the String which should be formatted and a format String to a method and it gives me the result.
Thanks in advance,
xtremliep

Answer 1

Darryl.Burke wrote:
System.out.println("20081208".replaceAll("(\\d{4})(\\d{2})(\\d{2})", "$1-$2-$3"));Note that if you're processing a large amount of data, this will almost certainly be slower than using a StringBuffer as already advised by two members.You can get a big performance boost by pre-compiling the regex and instantiating the Matcher ahead of time:
static final Matcher matcher = Pattern.compile("(\\d{4})(\\d{2})(\\d{2})").matcher("");
String newString = matcher.reset(oldString).replaceFirst("$1-$2-$3"); It will probably still be slower than the StringBuilder solution, but not by much. Of course, if the data is really huge, even a very small difference can have a noticeable impact.