code: public static int indexOf(String str, char searchChar, int startPos) {
        if (isEmpty(str)) {
            return -1;
        }
        return str.indexOf(searchChar, startPos);
    }
docs: <p>Finds the first index within a String from a start position,
  handling <code>null</code>.
  This method uses {@link String#indexOf(int, int)}.</p>
  
  <p>A <code>null</code> or empty ("") String will return <code>-1</code>.
  A negative start position is treated as zero.
  A start position greater than the string length returns <code>-1</code>.</p>
  
  <pre>
  GosuStringUtil.indexOf(null, *, *)          = -1
  GosuStringUtil.indexOf("", *, *)            = -1
  GosuStringUtil.indexOf("aabaabaa", 'b', 0)  = 2
  GosuStringUtil.indexOf("aabaabaa", 'b', 3)  = 5
  GosuStringUtil.indexOf("aabaabaa", 'b', 9)  = -1
  GosuStringUtil.indexOf("aabaabaa", 'b', -1) = 2
  </pre>
  
  @param str  the String to check, may be null
  @param searchChar  the character to find
  @param startPos  the start position, negative treated as zero
  @return the first index of the search character,
  -1 if no match or <code>null</code> string input
  @since 2.0