code: private String stringReplace(final String source, final String find, final String replace) {
      if (source == null || find == null || replace == null)
        return source;
      final int index = source.indexOf(find);
      if (index == -1)
        return source; // no occurence, don't do anything;
      if (index == 0)
        return replace + source.substring(find.length());
      return source.substring(0, index) + replace + source.substring(index + find.length());
    }
docs: Replaces a first occurence of a String with another string