code: public static boolean isColumnNullable (Connection conn, String table,
                                              String column)
          throws SQLException
      {
          ResultSet rs = getColumnMetaData(conn, table, column);
          try {
              return rs.getString("IS_NULLABLE").equals("YES");
          } finally {
              rs.close();
          }
      }
docs: Determines whether or not the specified column accepts null values.
  
  @return true if the column accepts null values, false if it does not (or its nullability is
  unknown)