private final DoubleValue d = new DoubleValue();
@Override
public void join(Record custRecord, Record olRecord, Collector<Record> out) throws Exception
{
final Tuple t = olRecord.getField(1, Tuple.class);
final double extPrice = Double.parseDouble(t.getStringValueAt(0));
final double discount = Double.parseDouble(t.getStringValueAt(1));
this.d.setValue(extPrice * (1 - discount));
custRecord.setField(2, this.d);
out.collect(custRecord);
}