code: private String getSelector(String[] columns,
                                 String[] values,
                                 String uniqueColumn) throws SQLException {
          String selector = null;
          for (int i = 0; i < columns.length; i++) {
              if (columns[i].equals(uniqueColumn)) {
                  selector = values[i];
              }
          }
          if (selector != null) {
              return selector;
          } else {
              throw new SQLException("Unique column does not exist in given "
                      + "column array");
          }
      }
docs: Gets the value in the given array whose associated column name matches
  the given uniqueColumn name.
  
  @throws SQLException
  if the uniqueColumn doesn't exist in the given column array.