Best practice for passing a type as a parameter in Java

Question

I have a class that's supposed to recieve in the c'tor an implementation type (concrete class type) of some IStratagy interface, and create some objects of these recieved types. Something like that:

Class SomeClass {
    public SomeClass(Class<IStrategy> strategyClass) {
        strategyClass.newInstance();
        // catch nasty reflection exceptions...
    }
}

I want to make sure that the parameter implements IStrategy. I could recieve a parameter "IStrategy concreteStrategy" and then concreteStrategy.getClass().newInstance() but then it's still reflection which i'm trying to avoid.. What is the best practice for this problem in Java?

Answer 1

I think you should use the following approach:

if( IStrategy.class.isAssignableFrom(strategyClass) ) {
          .....
}

Basically this is like instanceof, but without creating the actual instance of your concrete strategy implementation.

Hope this helps

Answer 2

Why not more simple like that:

Class SomeClass {
   public SomeClass( IStrategy strategyClass ) {
      ...
   }
}