How to use a regex to search backwards effectively?

Question

I\'m searching forward in an array of strings with a regex, like this:

for (int j = line; j < lines.length; j++) {  
    if (lines[j] == null || lines[j].         


        

Answer 1

Java's regular expression engine cannot search backwards. In fact, the only regex engine that I know that can do that is the one in .NET.

Instead of searching backwards, iterate over all the matches in a loop (searching forward). If the match is prior to the position you want, remember it. If the match is after the position you want, exit from the loop. In pseudo code (my Java is a little rusty):

storedmatch = ""
while matcher.find {
  if matcher.end < offset {
    storedmatch = matcher.group()
  } else {
    return storedmatch
  }
}