code: public StringProcessChain replacIgnoreCase(final String target, final String replacement) {
  
      StringBuilder result = new StringBuilder();
      String temp = source;
      int indexOfIgnoreCase = 0;
      while (true) {
        indexOfIgnoreCase = StringUtils.indexOfIgnoreCase(temp, target);
        if (indexOfIgnoreCase == StringUtils.INDEX_OF_NOT_FOUND) {
          result.append(temp);
          break;
        }
        result.append(temp.substring(0, indexOfIgnoreCase));
        result.append(replacement);
        temp = temp.substring(indexOfIgnoreCase + target.length());
      }
      source = result.toString();
      return this;
    }
docs: Replaces each substring of given source string that matches the given
  regular expression ignore case sensitive with the given replacement.<br>
  
  @param target target string want to be replaces.
  @param replacement string of replace to.
  @return a new string has been replaced each substring of given source
  string that matches the given regular expression ignore case
  sensitive with the given replacement.