Hi i am using commons collections generics 4.01. 

I have a dto object. 

```
Class PricingDto {
   private Double tax;
   private Double price;
   private Double tip;

   // getters and setters
}

```

i have a list of `List<PricingDto> pricingDtos = this.pricingService.getAllPricings();`

than i have a private static class. 

```
import org.apache.commons.collections15.Transformer;
import org.apache.commons.collections15.list.TransformedList;

class TotalServiceImpl implements TotalService {
    public static final PricingDtoTransformer PRICING_DTO_TRANSFORMER =
        new PricingDtoTransformer();
    private static class PricingDtoTransformer
        implements Transformer<PricingDto, Double> {
        public PricingDtoTransformer() {}

        @Override
        public Double transform(final PricingDto pricingDto) {
            return pricingDto.getTax()
                     + pricingDto.getPrice()
                     + pricingDto.getTips();
        }
    }

    @Override
    public List<Double> getListDouble(final List<PricingDto> pricingDtos) {
        final List<Double> totalList = 
            TransformedList.decorate(pricingDtos, PRICING_DTO_TRANSFORMER);
            for (Double d : totalList) {
                // print them. 
            }
        }
    }
}

```

My problem is i get class cast exception, because each item in totalList is a PricingDto and not Double. 

2.) What did i do wrong. Whats the correct way to implement custom transformer for generics commons-collections.