code: public static int lastIndexOf(final CharSequence seq, final CharSequence searchSeq) {
          if (seq == null || searchSeq == null) {
              return INDEX_NOT_FOUND;
          }
          return CharSequenceUtils.lastIndexOf(seq, searchSeq, seq.length());
      }
docs: <p>Finds the last index within a CharSequence, handling {@code null}.
  This method uses {@link String#lastIndexOf(String)} if possible.</p>
  
  <p>A {@code null} CharSequence will return {@code -1}.</p>
  
  <pre>
  StringUtils.lastIndexOf(null, *)          = -1
  StringUtils.lastIndexOf(*, null)          = -1
  StringUtils.lastIndexOf("", "")           = 0
  StringUtils.lastIndexOf("aabaabaa", "a")  = 7
  StringUtils.lastIndexOf("aabaabaa", "b")  = 5
  StringUtils.lastIndexOf("aabaabaa", "ab") = 4
  StringUtils.lastIndexOf("aabaabaa", "")   = 8
  </pre>
  
  @param seq  the CharSequence to check, may be null
  @param searchSeq  the CharSequence to find, may be null
  @return the last index of the search String,
  -1 if no match or {@code null} string input
  @since 2.0
  @since 3.0 Changed signature from lastIndexOf(String, String) to lastIndexOf(CharSequence, CharSequence)