generate a class during runtime based on logic java

Question

Assuming that I have a very basic case of polymorphism. How do I dynamically set which class to run during runtime?

E.g :

public interface Car {
      abstract String carName(); 
}

public class BMW implements Car{
    String carlogic(){
      // logic
    }
}


public class Audi implements Car{
    String carLogic(){
      //logic
   }
}

During runtime, I receive a string which is a car name. E.g. 'Audi','Bmw' etc. If i receive 'Audi' i want to call Audi.carLogic and 'BMW' BMW.carLogic. Now the easy way is to create this via switch cases but that seems rather messy? I know that this can also be done using reflections. But for the purpose of me learning, how would you approach this?

pczeus · Accepted Answer · 2016-02-13 17:42:00Z

2

In a 'formal' application, I would be using Spring and @Qualifier annotation to choose the right implementation class. That's a lot of bloat to add to just a test case or simple application though.

Without using a framework, you would want to use a Factory pattern or similar pattern. A good example that closely matches your car scenario can be found here:

http://howtodoinjava.com/design-patterns/creational/implementing-factory-design-pattern-in-java/

Finally, because you appear to be prefixing the car implementation class to match the input String, reflection within the factory is not a bad choice. (P.S. using Groovy instead of just Java would make this even easier).

answered Feb 13, 2016 at 17:42

pczeus

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