code: public static int lastIndexOf(String str, String searchStr, int startPos) {
          if (str == null || searchStr == null) {
              return INDEX_NOT_FOUND;
          }
          return str.lastIndexOf(searchStr, startPos);
      }
docs: <p>Finds the first index within a String, handling <code>null</code>.
  This method uses {@link String#lastIndexOf(String, int)}.</p>
  
  <p>A <code>null</code> String will return <code>-1</code>.
  A negative start position returns <code>-1</code>.
  An empty ("") search String always matches unless the start position is negative.
  A start position greater than the string length searches the whole string.</p>
  
  <pre>
  StringUtils.lastIndexOf(null, *, *)          = -1
  StringUtils.lastIndexOf(*, null, *)          = -1
  StringUtils.lastIndexOf("aabaabaa", "a", 8)  = 7
  StringUtils.lastIndexOf("aabaabaa", "b", 8)  = 5
  StringUtils.lastIndexOf("aabaabaa", "ab", 8) = 4
  StringUtils.lastIndexOf("aabaabaa", "b", 9)  = 5
  StringUtils.lastIndexOf("aabaabaa", "b", -1) = -1
  StringUtils.lastIndexOf("aabaabaa", "a", 0)  = 0
  StringUtils.lastIndexOf("aabaabaa", "b", 0)  = -1
  </pre>
  
  @param str  the String to check, may be null
  @param searchStr  the String to find, may be null
  @param startPos  the start position, negative treated as zero
  @return the first index of the search String,
  -1 if no match or <code>null</code> string input
  @since 2.0