code: public static String reverseDelimited(String str, char separatorChar) {
          if (str == null) {
              return null;
          }
          // could implement manually, but simple way is to reuse other,
          // probably slower, methods.
          String[] strs = split(str, separatorChar);
          ArrayUtils.reverse(strs);
          return join(strs, separatorChar);
      }
docs: <p>Reverses a String that is delimited by a specific character.</p>
  
  <p>The Strings between the delimiters are not reversed.
  Thus java.lang.String becomes String.lang.java (if the delimiter
  is <code>'.'</code>).</p>
  
  <pre>
  StringUtils.reverseDelimited(null, *)      = null
  StringUtils.reverseDelimited("", *)        = ""
  StringUtils.reverseDelimited("a.b.c", 'x') = "a.b.c"
  StringUtils.reverseDelimited("a.b.c", ".") = "c.b.a"
  </pre>
  
  @param str  the String to reverse, may be null
  @param separatorChar  the separator character to use
  @return the reversed String, <code>null</code> if null String input
  @since 2.0