Print regex matches in java

Question

So I have an IP address as a string. I have this regex (\d{1-3})\.(\d{1-3})\.(\d{1-3})\.(\d{1-3}) How do I print the matching groups?

Thanks!

Answer 1

If you use Pattern and Matcher to do your regex, then you can ask the Matcher for each group using the group(int group) method

So:

Pattern p = Pattern.compile("(\\d{1-3}).(\\d{1-3}).(\\d{1-3}).(\\d{1-3})"); 
Matcher m = p.matcher("127.0.0.1"); 
if (m.matches()) {   
  System.out.print(m.group(1));  
  // m.group(0) is the entire matched item, not the first group.
  // etc... 
}

Answer 2

import java.util.regex.*;
try {
    Pattern regex = Pattern.compile("(\\d\\{1-3\\})\\.(\\d\\{1-3\\})\\.(\\d\\{1-3\\})\\.(\\d\\{1-3\\})");
    Matcher regexMatcher = regex.matcher(subjectString);
    while (regexMatcher.find()) {
     for (int i = 1; i <= regexMatcher.groupCount(); i++) {
      // matched text: regexMatcher.group(i)
      // match start: regexMatcher.start(i)
      // match end: regexMatcher.end(i)
     }
    } 
} catch (PatternSyntaxException ex) {
    // Syntax error in the regular expression
}

Answer 3

http://www.regular-expressions.info/java.html

Answer 4

You might find my blog post here useful:

Regular expressions capturing in Java for Perl hackers