Re: Splitting a String with a Regex

Jussi Piitulainen <>
04 May 2006 10:06:11 +0300
Oliver Wong writes:

Jussi Piitulainen wrote:

Oliver Wong writes:

Danno wrote:


String s = "<?xml...><response
String[] tokens = s.split("<\\?xml[.]*>");


    Probably won't work. XML is a context-free language, not a
regular language.

It might well work (maybe better with "<[?]xml.*?>" or so) for a
particular kind of input sequence where any <?xml...?> thing only
appears in the beginning of each individual part and nowhere else,
and the ... in any of them doesn't contain >.

Just looping to find each string "<?xml" would then also work.

    Oops, I had thought that the regular expression Danno wrote was
to get the content of the strings themselves, rather than the
delimiters. So actually, Danno's code may probably work, as long as
the "[.]*" part isn't greedy, along with the other qualifications
you gave.

Yes, the pattern in .split() is just the delimiter.

Greed is one fault. Character class brackets are another: the pattern
"[.]*" matches any number of dots only, while ".*" matches any number
of almost any characters. Both faults are easily fixed.

The method does not return the actual delimiters, so the text that was
matched by ".?" would be lost. If all the other conditions are right,
then "(<[?]xml.*?)((?=<[?]xml)|\\z)" should match exactly the wanted
parts of the document: from "<?xml" up to another "<?xml" or the end
of all input. Let me see. I shorten the tags a bit to keep the line
lengths under control:

import java.util.regex.Matcher;
import java.util.regex.Pattern;
class Split {
  public static void main(String [] _) {
    Matcher m = Pattern
      .matcher("<?x 1?><r 1/><?x 2?><r 2/><?x 3?><r 3/>");
    while (m.find()) {
       System.out.println("(" + + ")(" + + ")");

Ok, it appears to work - if all the conditions about the input are

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