Matching between char sequences - first occurence before

Question

I have a string like:

"This is AA and this is AA and this is AA and this is the END blah blah"

I want to match:

"AA and this is the END"

ie, ending in END, back to the first occurance of AA before END. (Language is Java)

Answer 1

Try this:

AA(?:(?!AA).)*END

A demo:

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main { 
    public static void main(String[] args) {
        String text = "This is AA and this is AA and this is AA and this is the END blah blah";
        Matcher m = Pattern.compile("AA(?:(?!AA).)*END").matcher(text);
        while(m.find()) {
            System.out.println("match ->"+m.group()+"<-");
        }
    }
}

And if there can be line breaks between the AA and END, add a (?s) (DOT-ALL flag) at the start of your regex.

A short explanation:

AA          # match 'AA'
(?:         # open non-capturing group 1
  (?!AA).   #   if 'AA' cannot be seen, match any char (except line breaks)
)*          # close non-capturing group 1 and repeat it zero or more times
END         # match 'END'

Answer 2

An alternative answer:

str.substring(0, str.lastIndexOf("END")).lastIndexOf("AA");

This creates the substring extending to "END" and finds the last occurrence of your search string within that substring.