How do you name different classes / interfaces you create?
Sometimes I don't have implementation information to add to the implementation name - like interface FileHandler
and class SqlFileHandler
.
When this happens I usually name the interface in the "normal" name, like Truck
and name the actual class TruckClass
.
How do you name interfaces and classes in this regard?
Name your Interface
what it is. Truck
. Not ITruck
because it isn't an ITruck
it is a Truck
.
An Interface
in Java is a Type. Then you have DumpTruck
, TransferTruck
, WreckerTruck
, CementTruck
, etc that implement Truck
.
When you are using the Interface
in place of a sub-class you just cast it to Truck
. As in List<Truck>
. Putting I
in front is just Hungarian style notation tautology that adds nothing but more stuff to type to your code.
All modern Java IDE's mark Interfaces and Implementations and what not without this silly notation. Don't call it TruckClass
that is tautology just as bad as the IInterface
tautology.
If it is an implementation it is a class. The only real exception to this rule, and there are always exceptions, could be something like AbstractTruck
. Since only the sub-classes will ever see this and you should never cast to an Abstract
class it does add some information that the class is abstract and to how it should be used. You could still come up with a better name than AbstractTruck
and use BaseTruck
or DefaultTruck
instead since the abstract
is in the definition. But since Abstract
classes should never be part of any public facing interface I believe it is an acceptable exception to the rule. Making the constructors protected
goes a long way to crossing this divide.
And the Impl
suffix is just more noise as well. More tautology. Anything that isn't an interface is an implementation, even abstract classes which are partial implementations. Are you going to put that silly Impl
suffix on every name of every Class?
The Interface
is a contract on what the public methods and properties have to support, it is also Type information as well. Everything that implements Truck
is a Type of Truck
.
Look to the Java standard library itself. Do you see IList
, ArrayListImpl
, LinkedListImpl
? No, you see List
and ArrayList
, and LinkedList
. Here is a nice article about this exact question. Any of these silly prefix/suffix naming conventions all violate the DRY principle as well.
Also, if you find yourself adding DTO
, JDO
, BEAN
or other silly repetitive suffixes to objects then they probably belong in a package instead of all those suffixes. Properly packaged namespaces are self documenting and reduce all the useless redundant information in these really poorly conceived proprietary naming schemes that most places don't even internally adhere to in a consistent manner.
If all you can come up with to make your Class
name unique is suffixing it with Impl
, then you need to rethink having an Interface
at all. So when you have a situation where you have an Interface
and a single Implementation
that is not uniquely specialized from the Interface
you probably don't need the Interface
.