Yes, you can use multi-character names for type variables, as long as they are clearly distinguished from class names.
This differs from the convention suggested by Sun with the introduction of generics in 2004. However:
- More than one convention exists.
- Multi-character names are consistent with other Java styles, such as Google’s style for Java.
- The readable names are (surprise!) more readable.
Readability
In some interfaces I wrote I’d like to name generic type parameter with more than one character to make the code more readable.
Readability is good.
Compare:
public final class EventProducer<L extends IEventListener<E>,E>
implements IEventProducer<L,E> {
to:
public final class EventProducer<LISTENER extends IEventListener<EVENT>,EVENT>
implements IEventProducer<LISTENER, EVENT> {
or, with Google’s multi-character convention:
public final class EventProducer<ListenerT extends IEventListener<EventT>,EventT>
implements IEventProducer<ListenerT, EventT> {
public final class EventProducer<ListenerT extends IEventListener<EventT>,EventT>
implements IEventProducer<ListenerT, EventT> {
Google style
The Google Java Style Guide allows both single-letter names and multi-character class-like names ending in T.
5.2.8 Type variable names
Each type variable is named in one of two styles:
A single capital letter, optionally followed by a single numeral (such as E, T, X, T2)
A name in the form used for classes (see Section 5.2.2, Class names), followed by the capital letter T (examples: RequestT, FooBarT).
Issues
“Without this convention, it would be difficult to tell the difference between a type variable and an ordinary class or interface name.” – from the Oracle tutorials, “Generic types”
Single-character names are not the only way to distinguish type parameters from class names, as we’ve seen above.
Why not just document the type parameter meaning in the JavaDoc?
It’s true that the @param JavaDoc elements can provide a longer description. But it’s also true that the JavaDocs are not necessarily visible. (For example, there’s a content assist in Eclipse that shows the type parameter names.)
Multi-character type parameter names don’t follow the Oracle convention!
Many of Sun’s original conventions are followed nearly universally in Java programming.
However, this particular convention is not.
The best choice among competing conventions is a matter of opinion. The consequences of choosing a convention other than Oracle’s in this case are minor. You and your team can choose a convention that best meets your needs.
