Jun Qian (钱骏) 's Weblog

Word Wrap Long String, the Easy Way

Today I had to convert a third-party library license file from HTML to plain text according to this NetBeans policy. The problem I ran into was that the text I grabbed from the HTML file consists of long lines of strings, which doesn't satisfy the rule of "Lines should not exceed 80 characters."

To my surprise, none of the editor tools I use allow me to do automatic line breaking with word wrap, so I had to write my own code to do this. The following code using regular expression is probably the easiest to write, though not the most efficient:

    String line = ...;
    Pattern p = Pattern.compile( "(.{0,80}\\b\\s*)|(.{80}\\B)" ); 
    Matcher m = p.matcher(line);
    while (m.find()) {
        System.out.println(s.substring(m.start(), m.end()));
    }

The first part of the regular express ".{0,80}\b\s*" uses a greedy quantifier to grab as many words as possible before reaching the line limit. "\s*" is added to avoid starting white spaces after inserted newline characters. It does introduce trailing white spaces though, which should probably be trimmed. I hope java.Lang.String had a trimEnd() method to trim trailing white spaces of a string.

The second part of the regular expression ".{80}\B" was not really necessary for my purpose but could be useful in a different scenario. It forces line break in the middle of a word if the word is longer than the desired line limit.

One possible usage of this code is automatic word wrap for Swing tooltip. There will be no need to create a HTML string and do manual line break, which is something I have been doing so far. This is not perfect though because it doesn't take individual character's font width into account, but it does provide a roughly consistent tooltip look and feel across the application. Do you have a better solution for handling tooltip?

Posted at 01:16AM Aug 15, 2007 by Jun Qian in Java  |  Comments[2]