Sometimes less is more ;)

Wrapper.java

public class Wrapper {
  public static String wrap(String s, int col) {
    return new Wrapper(col).wrap(s);
  }

  private int col;

  private Wrapper(int col) {
    this.col = col;
  }

  private String wrap(String s) {
    if (s.length() <= col)
      return s;
    int space = (s.substring(0, col + 1).lastIndexOf(' '));
    if (space != -1)
      return s.substring(0, space) + "\n" + wrap(s.substring(space + 1));
    else
      return s.substring(0, col) + "\n" + wrap(s.substring(col));
  }
}