public boolean wasNull() throws SQLException {
        checkState();

        return rs.wasNull();
    }
Reports whether the last column read from this rowset's
<code>ResultSet</code> object had a value of SQL <code>NULL</code>.
Note that you must first call one of the <code>getXXX</code> methods
on a column to try to read its value and then call
the method <code>wasNull</code> to see if the value read was
SQL <code>NULL</code>.

@return <code>true</code> if the last column value read was SQL
        <code>NULL</code> and <code>false</code> otherwise
@throws SQLException if a database access error occurs
           or this rowset does not have a currently valid connection,
           prepared statement, and result set
src/main/java/org/replicadb/rowset/sun/rowset/JdbcRowSetImpl.java