checking class type alternative to instanceof

[Timasmith]

Hi,

Can I check if a class is an implementation of an interface by name
without instantiating it?

So I can do this:

if (Class.forName("com.company.package.myclass").newInstance()
instanceof MyInterface) {
// class implements interface
}

but it seems create an instance of it by reflection is suboptimal.

Can I do the same thing without calling newInstance()?

thanks

 

[Thomas Hawtin]

if (Class.forName("com.company.package.myclass").newInstance()
instanceof MyInterface) {
// class implements interface
}

but it seems create an instance of it by reflection is suboptimal.

Can I do the same thing without calling newInstance()?

Class.isAssignableFrom

I believe you can also get away without initialising the class with
Class.forName(String,false,ClassLoader).

Tom Hawtin

 

[Eric Sosman]

Timasmith wrote On 11/13/06 16:56,:

Hi,

Can I check if a class is an implementation of an interface by name
without instantiating it?

So I can do this:

if (Class.forName("com.company.package.myclass").newInstance()
instanceof MyInterface) {
// class implements interface
}

but it seems create an instance of it by reflection is suboptimal.

Can I do the same thing without calling newInstance()?

You could use getInterfaces() on the Class object and rummage
through the array it returns.

I'm worried about your use of the word "suboptimal," though.
If you're making so many of these inquiries that optimality is
a concern, you're probably making too many. What is it about
the design that requires you to do this so often?

 

[Timasmith]

You could use getInterfaces() on the Class object and rummage
through the array it returns.

I'm worried about your use of the word "suboptimal," though.
If you're making so many of these inquiries that optimality is
a concern, you're probably making too many. What is it about
the design that requires you to do this so often?

It is not so much that I do it so often in the code, I just do it
somewhere which is called a large number of times and I try to avoid
extra object creation where feasible.