Large string split into lines with maximum length in java

Question

String input = \"THESE TERMS AND CONDITIONS OF SERVICE (the Terms) ARE A LEGAL AND BINDING AGREEMENT BETWEEN YOU AND NATIONAL GEOGRAPHIC governing your use of this s         


        

Answer 1

I have recently written a few methods to do this that, if no whitespace characters are present in one of the lines, opts for splitting on other non-alphanumeric characters prior to resorting to a mid-word split.

Here is how it turned out for me:

(Uses the lastIndexOfRegex() methods I posted here.)

/**
 * Indicates that a String search operation yielded no results.
 */
public static final int NOT_FOUND = -1;



/**
 * Version of lastIndexOf that uses regular expressions for searching.
 * By Tomer Godinger.
 * 
 * @param str String in which to search for the pattern.
 * @param toFind Pattern to locate.
 * @return The index of the requested pattern, if found; NOT_FOUND (-1) otherwise.
 */
public static int lastIndexOfRegex(String str, String toFind)
{
    Pattern pattern = Pattern.compile(toFind);
    Matcher matcher = pattern.matcher(str);

    // Default to the NOT_FOUND constant
    int lastIndex = NOT_FOUND;

    // Search for the given pattern
    while (matcher.find())
    {
        lastIndex = matcher.start();
    }

    return lastIndex;
}

/**
 * Finds the last index of the given regular expression pattern in the given string,
 * starting from the given index (and conceptually going backwards).
 * By Tomer Godinger.
 * 
 * @param str String in which to search for the pattern.
 * @param toFind Pattern to locate.
 * @param fromIndex Maximum allowed index.
 * @return The index of the requested pattern, if found; NOT_FOUND (-1) otherwise.
 */
public static int lastIndexOfRegex(String str, String toFind, int fromIndex)
{
    // Limit the search by searching on a suitable substring
    return lastIndexOfRegex(str.substring(0, fromIndex), toFind);
}

/**
 * Breaks the given string into lines as best possible, each of which no longer than
 * <code>maxLength</code> characters.
 * By Tomer Godinger.
 * 
 * @param str The string to break into lines.
 * @param maxLength Maximum length of each line.
 * @param newLineString The string to use for line breaking.
 * @return The resulting multi-line string.
 */
public static String breakStringToLines(String str, int maxLength, String newLineString)
{
    StringBuilder result = new StringBuilder();
    while (str.length() > maxLength)
    {
        // Attempt to break on whitespace first,
        int breakingIndex = lastIndexOfRegex(str, "\\s", maxLength);

        // Then on other non-alphanumeric characters,
        if (breakingIndex == NOT_FOUND) breakingIndex = lastIndexOfRegex(str, "[^a-zA-Z0-9]", maxLength);

        // And if all else fails, break in the middle of the word
        if (breakingIndex == NOT_FOUND) breakingIndex = maxLength;

        // Append each prepared line to the builder
        result.append(str.substring(0, breakingIndex + 1));
        result.append(newLineString);

        // And start the next line
        str = str.substring(breakingIndex + 1);
    }

    // Check if there are any residual characters left
    if (str.length() > 0)
    {
        result.append(str);
    }

    // Return the resulting string
    return result.toString();
}

Answer 2

Best : use Apache Commons Lang :

org.apache.commons.lang.WordUtils

/**
 * <p>Wraps a single line of text, identifying words by <code>' '</code>.</p>
 * 
 * <p>New lines will be separated by the system property line separator.
 * Very long words, such as URLs will <i>not</i> be wrapped.</p>
 * 
 * <p>Leading spaces on a new line are stripped.
 * Trailing spaces are not stripped.</p>
 *
 * <pre>
 * WordUtils.wrap(null, *) = null
 * WordUtils.wrap("", *) = ""
 * </pre>
 *
 * @param str  the String to be word wrapped, may be null
 * @param wrapLength  the column to wrap the words at, less than 1 is treated as 1
 * @return a line with newlines inserted, <code>null</code> if null input
 */
public static String wrap(String str, int wrapLength) {
    return wrap(str, wrapLength, null, false);
}