Checking a number sequence with regular expressions

Question

Hello,
Suppose I have a text in the pattern:
A1=ha,A2=bla,A3=cha,...
I don't know how many sections of "A#=$" (# denotes number, $ denotes text) will be in the text, but I want to verify that the numbers of the A's form the natural ascending number sequence (i.e 1,2,3,...). I prefer to use regular expressions to do this, but if there's another way, I will be glad to hear it too.
Therefore my question is: How can I use regular expressions to check for a sequence of numbers? I know I can search for groups I've caught previously in the expression, but how can I compute the next number in the sequence from the group and search for the result?
Thank you very much!

Answer 1

What I'd do--and I'm not saying this is optimal, just what pops immediately to mind--is have a regex that matches "A(\\d+)=" (assuming the ha, bla, cha can never be "A1" etc.--if they can, you can still do it, but it's more complicated), then you iterate with the Matcher, and each time, you get the Integer.valueOf what you matched. You keep track of the last value, and compare the current to the last. If current is < last (or <= last, depending on your requirements), fail.
Something like this. I don't recall Matcher's methods off the top of my head, so you'll have to fix the details.
Matcher m = Pattern.matcher("A(\\d+)=");
int maxSoFar = Integer.MIN_VALUE;
while (m.matches(input)) {
    int current = Integer.parseInt(m.getMatchedField("$1"));
    if (current <= maxSoFar) {
        // fail
    else {
        maxSoFar = current;
} maxSoFar =