code: static String ensureIncludesAt(String pSource, String pSubstring, int pPosition) {
          StringBuilder newString = new StringBuilder(pSource);
  
          try {
              String existingSubstring = pSource.substring(pPosition, pPosition + pSubstring.length());
  
              if (!existingSubstring.equalsIgnoreCase(pSubstring)) {
                  newString.insert(pPosition, pSubstring);
              }
          }
          catch (Exception e) {
              // Do something!?
          }
          return newString.toString();
      }
docs: Ensures that a string includes a given substring at a given position.
  <p/>
  Extends the string with a given string if it is not already there.
  E.g an URL "www.vg.no", to "http://www.vg.no".
  
  @param pSource    The source string.
  @param pSubstring The substring to include.
  @param pPosition  The location of the fill-in, the index starts with 0.
  @return the string, with the substring at the given location.