Question

In python , I can use a replacer function in sub(), that is very powerful for some situation, like this:

def replacer(match):
    s = match.group(0)
    if s.startswith('/'):
        return ""
    else:
        return s
return re.sub(pattern, replacer, text)

how to do this in Java?

Answer 1

In Java, there is an idiom:

Pattern pattern = Pattern.compile(yourPattern);
Matcher matcher = patern.matcher(yourString);
while (matcher.find()) {
  String group = matcher.group(0);
  // do your if statement
}

One tip that’s not readily apparent from the documentation – if yourString has special (reg exp) characters in it, it is important to use matcher.appendReplacement(stringBuffer) and matcher.appendTail(stringBuffer) to avoid errors.