Truncate String on closest word boundary

Question

Is it possible to truncate a Java string to the closest word boundary after a number of characters. Similar to the PHP wordwrap() function, shown in this example.

score 14 · Accepted Answer · answered Feb 05 '09 at 05:50

14

Use a java.text.BreakIterator, something like this:

String s = ...;
int number_chars = ...;
BreakIterator bi = BreakIterator.getWordInstance();
bi.setText(s);
int first_after = bi.following(number_chars);
// to truncate:
s = s.substring(0, first_after);

answered Feb 05 '09 at 05:50

David Z

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This is great thanks, although would aa bi.truncateAt() have been too much to ask for? :) – Xenph Yan Feb 05 '09 at 06:02
1

Make sure you test that number_chars is not larger than s.length(), otherwise you get an exception. FYI, I tried to edit the java to reflect this fact, but the edit was rejected. – mooreds Nov 07 '11 at 05:43

score 4 · Answer 2 · answered Feb 05 '09 at 05:54

4

You can use regular expression

Matcher m = Pattern.compile("^.{0,10}\\b").matches(str);
m.find();
String first10char = m.group(0);

answered Feb 05 '09 at 05:54

Dennis C

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score 3 · Answer 3 · answered May 12 '12 at 18:15

With the first approach you will end up with a length bigger than number_chars. If you need an exact maximum or less, like for a Twitter message, see my implementation below.

Note that the regexp approach uses a space to delimit the words, while BreakIterator breaks up words even if they have commas and other characters. This is more desirable.

Here is my full function:

/**
     * Truncate text to the nearest word, up to a maximum length specified.
     * 
     * @param text
     * @param maxLength
     * @return
     */
    private String truncateText(String text, int maxLength) {
        if(text != null && text.length() > maxLength) {
            BreakIterator bi = BreakIterator.getWordInstance();
            bi.setText(text);

            if(bi.isBoundary(maxLength-1)) {
                return text.substring(0, maxLength-2);
            } else {
                int preceding = bi.preceding(maxLength-1);
                return text.substring(0, preceding-1);
            }
        } else {
            return text;
        }
    }

score 0 · Answer 4 · answered Mar 06 '18 at 11:08

Solution with BreakIterator is not really straightforward when breaking sentence is URL, it breaks URL not very nice way. I rather used mine solution:

public static String truncateText(String text, int maxLength) {
    if (text != null && text.length() < maxLength) {
        return text;
    }
    List<String> words = Splitter.on(" ").splitToList(text);
    List<String> truncated = new ArrayList<>();
    int totalCount = 0;
    for (String word : words) {
        int wordLength = word.length();
        if (totalCount + 1 + wordLength > maxLength) { // +1 because of space
            break;
        }
        totalCount += 1; // space
        totalCount += wordLength;
        truncated.add(word);
    }
    String truncResult = Joiner.on(" ").join(truncated);
    return truncResult + " ...";
}

Splitter/Joiner is from guava. I am also adding ... at the end in my use cas (can be ommited).

Truncate String on closest word boundary

4 Answers4