Question

I am stuck up with a problem while using Regular Expression.
My requirement is : split a long string into maximum size of 125 letters and then insert a line break in between them.
while splitting, it shouldn’t split between the words. in short, i want to split a string into small strings whose length is 125 or at the end of word before 125th letter. Hope i didnt confused

i used one regexp to solve this, and believe me am an absolute zero in this.
i just got one code and copy pasted 😉

StringBuffer result = null;  
while(mailBody.trim().length() > 0){  
    Matcher m = Pattern.compile("^.{0,125}\\b").matcher(mailBody);  
    m.find();  
    String oneLineString = m.group(0);  
    if(result == null)  
        result = new StringBuffer(oneLineString);  
    else  
        result.append("\n"+ oneLineString);  
    mailBody = mailBody.substring(oneLineString.length(),
                                  mailBody.length()).trim();  
}    

this is my code, and it’s working perfectly unless the starting string ends with a full stop(.).
In that case it is giving an error like : No match found.

Please help.

Regards,
Anoop P K

Answer 1

Can you try using the following instead?

Matcher m = Pattern.compile("(?:^.{0,125}\\b)|(?:^.{0,125}$)").matcher(mailBody);  

Here we use your original match OR we match a string whose total length is 125 characters or fewer. The (?:X) items are non-capturing groups, so that I can use the | operator on the large groups.

(See documentation for the Pattern class here.)

---

Addendum: @Anoop: Quite right, having sentence-ending punctuation left off on its own line is undesirable behavior. You can try this instead:

if(result == null)  
   result = new StringBuffer("");

mailBody = mailBody.trim();

while(mailBody.length() > 125) {

    // Try not to break immediately before closing punctuation
    Matcher m = Pattern.compile("^.{1,125}\\b(?![-\\.?;&)])").matcher(mailBody);
    String oneLineString;

    // Found a safe place to break string
    if (m.find()) {

        oneLineString = m.group(0);

    // Forced to break string in an ugly fashion
    } else {

        // Try to break at any word boundary at least
        m = Pattern.compile("^.{1,125}\\b").matcher(mailBody);

        if (m.find()) {

            oneLineString = m.group(0);

        // Last ditch scenario, just break at 125 characters
        } else {

            oneLineString = mailBody.substring(0,124);

        }

    }

    result.append(oneLineString + "\n");
    mailBody = mailBody.substring(oneLineString.length(),
                                  mailBody.length()).trim();  
}

result.append(mailBody);