Regular Expressions on Punctuation

Question

So I'm completely new to regular expressions, and I'm trying to use Java's java.util.regex to find punctuation in input strings. I won't know what kind of punctuation I might get ahead of time, except that (1) !, ?, ., ... are all valid puncutation, and (2) "<" and ">" mean something special, and don't count as punctuation. The program itself builds phrases pseudo-randomly, and I want to strip off the punctuation at the end of a sentence before it goes through the random process.

I can match entire words with any punctuation, but the matcher just gives me indexes for that word. In other words:

Pattern p = Pattern.compile("(.*\\!)*?"); Matcher m = p.matcher([some input string]); 

will grab any words with a "!" on the end. For example:

String inputString = "It is a warm Summer day!"; Pattern p = Pattern.compile("(.*\\!)*?"); Matcher m = p.matcher(inputString); String match = inputString.substring(m.start(), m.end()); 

results in --> String match ~ "day!"

But I want to have Matcher index just the "!", so I can just split it off.

I could probably make cases, and use String.substring(...) for each kind of punctuation I might get, but I'm hoping there's some mistake in my use of regular expressions to do this.

Answer 1

Java does support POSIX character classes in a roundabout way. For punctuation, the Java equivalent of [:punct:] is \p{Punct}.

Please see the following link for details.

Here is a concrete, working example that uses the expression in the comments

import java.util.regex.Matcher; import java.util.regex.Pattern;  public class RegexFindPunctuation {      public static void main(String[] args) {         Pattern p = Pattern.compile("\\p{Punct}");          Matcher m = p.matcher("One day! when I was walking. I found your pants? just kidding...");         int count = 0;         while (m.find()) {             count++;             System.out.println("\nMatch number: " + count);             System.out.println("start() : " + m.start());             System.out.println("end()   : " + m.end());             System.out.println("group() : " + m.group());         }     } } 

Answer 2

I would try a character class regex similar to

"[.!?\\-]" 

Add whatever characters you wish to match inside the []s. Be careful to escape any characters that might have a special meaning to the regex parser.

You then have to iterate through the matches by using Matcher.find() until it returns false.