java regex matching each group starting with specific string

Question

I have a string like a1wwa1xxa1yya1zz.

I would like to get every groups starting with a1 until next a1 excluded. (In my example, i would be : a1ww, a1xx, a1yyand a1zz

If I use :

Matcher m = Pattern.compile("(a1.*?)a1").matcher("a1wwa1xxa1yya1zz");
while(m.find()) {
  String myGroup = m.group(1);
}

myGroup capture 1 group every two groups.
So in my example, I can only capture a1ww and a1yy.

Anyone have a great idea ?

Answer 1

Split is a good solution, but if you want to remain in the regex world, here is a solution:

Matcher m = Pattern.compile("(a1.*?)(?=a1|$)").matcher("a1wwa1xxa1yya1zz");
while (m.find()) {
  String myGroup = m.group(1);
  System.out.println("> " + myGroup);
}

I used a positive lookahead to ensure the capture is followed by a1, or alternatively by the end of line.

Lookahead are zero-width assertions, ie. they verify a condition without advancing the match cursor, so the string they verify remains available for further testing.