Re: Naming conventions for Interface + Implementation classes?
On Thu, 3 Feb 2011, Peter Duniho wrote:
On 2/3/11 5:14 PM, Robin Wenger wrote:
As I noticed there are two different naming conventions for an
Interface+Implementation pair:
1.) MyClass (=Interface) + MyClassImpl (=Implementation)
or
2.) IMyClass (=Interface) + MyClass (=Implementation)
The first one is (AFAIK) from Sun Who defined originally the second one?
I see it a lot in Microsoft land, so perhaps it originated there - they're
certainly fond of pseudo-Hungarian notation elsewhere, and this is
similar. I recall Delphi also had prefix letters (TSomeComponent and so
on); i don't know if this is related.
What is recommended (for which scenario)?
I don't think you'll find anyone using the word "Class" in an interface
name,
I assume that MyClass is a metasyntactic variable here.
nor the suffice "Impl" in the name of a class that implements an
interface.
You're kidding me, right? Try this on for size:
$ cd $JAVA_HOME
$ find . -type f -name \*.jar -print0 | xargs -0 -n1 jar tf | egrep "Impl.class$" | sort -u
With 1.6.0_22, that nets me 1423 hits. Now, not all of these are classes
which follow the pattern ${InterfaceName}Impl, but enough are to disprove
your belief.
In fact, let's see a bunch:
$ cd $JAVA_HOME
$ export CLASSPATH=$(find . -name \*.jar | tr '\n' :)
$ find . -type f -name \*.jar -print0 | xargs -0 -n1 jar tf \
| egrep "Impl.class$" | fgrep -v '$' | cut -d . -f 1 | tr / . \
| sort -u \
| while read c; do
iface=$(javap $c 2>/dev/null | egrep -o "implements [a-zA-Z0-9.]*" | cut -d ' ' -f 2);
if [[ $iface == ${c%%Impl} ]]; then
echo "$c implements $iface";
fi;
done
And that's a rough survey which ignores anything involving inner classes,
implementations which are in different packages to their interfaces, any
kind of addition to the class name, classes implementing another interface
ahead of their namesake, etc.
I hasten to add that i do not recommend this naming convention; i'm simply
demonstrating that it does occur in the wild.
In Java, what I often see with respect to interfaces and implementations
are names like "MyInterface" and "MySpecificKindOfMyInterface". E.g.
List vs ArrayList, Set vs HashSet, etc.
Yup. That's the right way to do it.
tom
--
I have a bias because it's a STUPID FUCKING IDEA. -- Brett Sikola