Programmer's Cookbook

Note that the Jakarta commons-lang package has similar functionality. I would only use this were using commons-lang was not an option.

This function takes a string value and a line length, and returns an array of lines. Lines are cut on word boundaries, where the word boundary is a space character. Spaces are included as the last character of a word, so most lines will actually end with a space. This isn't too problematic, but will cause a word to wrap if that space pushes it past the max line length.

String text = "this is a long line of text that needs to be wrapped";
String [] lines = wrapText(text, 20);
for (int i = 0; i < lines.length; i++) {
    System.out.println(lines[i]);
}

static String [] wrapText (String text, int len)
{
  // return empty array for null text
  if (text == null)
  return new String [] {};

  // return text if len is zero or less
  if (len <= 0)
  return new String [] {text};

  // return text if less than length
  if (text.length() <= len)
  return new String [] {text};

  char [] chars = text.toCharArray();
  Vector lines = new Vector();
  StringBuffer line = new StringBuffer();
  StringBuffer word = new StringBuffer();

  for (int i = 0; i < chars.length; i++) {
    word.append(chars[i]);

    if (chars[i] == ' ') {
      if ((line.length() + word.length()) > len) {
        lines.add(line.toString());
        line.delete(0, line.length());
      }

      line.append(word);
      word.delete(0, word.length());
    }
  }

  // handle any extra chars in current word
  if (word.length() > 0) {
    if ((line.length() + word.length()) > len) {
      lines.add(line.toString());
      line.delete(0, line.length());
    }
    line.append(word);
  }

  // handle extra line
  if (line.length() > 0) {
    lines.add(line.toString());
  }

  String [] ret = new String[lines.size()];
  int c = 0; // counter
  for (Enumeration e = lines.elements(); e.hasMoreElements(); c++) {
    ret[c] = (String) e.nextElement();
  }

  return ret;
}