Howe to correctly parameterise a Class

[Adam Lipscombe]

Folks


How do I correctly parameterise a Class?


I have code like this:

String classPath = "com.blah.bah.MyClass"
Class clazz = Class.forName(classPath);
Facade facade = (Facade) clazz.newInstance();


Facade is an interface and the class named by classPath will always implement this i/f.


Do I simply do: Class<Facade> clazz = Class.forName(classPath);


If not, what?



TIA - Adam

 

[Thomas Fritsch]

String classPath = "com.blah.bah.MyClass"
Class clazz = Class.forName(classPath);
Facade facade = (Facade) clazz.newInstance();


Facade is an interface and the class named by classPath will always
implement this i/f.


Do I simply do: Class<Facade> clazz = Class.forName(classPath);

Not quite.

If not, what?

You'll still need a cast:
Class<Facade> clazz = (Class<Facade>) Class.forName(classPath);
Facade facade = clazz.newInstance();

 

[Piotr Kobzda]

Adam Lipscombe wrote:
[...]

If not, what?

You'll still need a cast:
Class<Facade> clazz = (Class<Facade>) Class.forName(classPath);
Facade facade = clazz.newInstance();

I prefer to use a bit type-safer version of the above:

Class<? extends Facade> clazz
= Class.forName(classPath).asSubclass(Facade.class);
Facade facade = clazz.newInstance();


piotr

 

[Thomas Fritsch]

I prefer to use a bit type-safer version of the above:

Class<? extends Facade> clazz
= Class.forName(classPath).asSubclass(Facade.class);
Facade facade = clazz.newInstance();

Granted! I prefer yours, too.

 

[Adam Lipscombe]

Groovy! Many thanks....


Adam

 

[Daniel Pitts]

Adam Lipscombe wrote:
[...]

If not, what?

You'll still need a cast:
Class<Facade> clazz = (Class<Facade>) Class.forName(classPath);
Facade facade = clazz.newInstance();

I prefer to use a bit type-safer version of the above:

Class<? extends Facade> clazz
= Class.forName(classPath).asSubclass(Facade.class);
Facade facade = clazz.newInstance();


piotr

Not to mention that this is more correct.
The Class instance itself is the MyClass, not Facade, so Class<Facade>
is just plain wrong, where as Class<? extends Facade> is accurate.