Re: Yet another generics question: Needs unchecked conversion to conform to ...

Thanks for your replies,

Daniel Pitts a =E9crit :


I'll explain in an upcoming separate message.


The exat warning is:

Type safety: The expression of type capture-of ? extends
Generics.BeanFactory needs unchecked conversion to conform to
Generics.BeanFactory<? extends Generics.Bean>

The "ssce" (thank you for the info on this acronym) was there in the
first message: The "Generics" class compiles as is without any
dependanies, and the warning shows up in Eclipse (I did not try on any
other compiler). Here it is again with a slight modification in the
return type of the createFactory2 method :

public class Generics {

  public BeanFactory createFactory1(String beanClass) throws Exception{

    Class<?> bc = Class.forName(beanClass);
    Class<? extends BeanFactory> bfc =
      bc.asSubclass(BeanFactory.class);
    Constructor<? extends BeanFactory> cstr =
      bfc.getConstructor(new Class[]{});
    return cstr.newInstance(new Object[]{});
  }

  public BeanFactory<? extends Bean> createFactory2(String beanClass)
throws Exception{

    Class<?> bc = Class.forName(beanClass);
    Class<? extends BeanFactory> bfc =
      bc.asSubclass(BeanFactory.class);
    Constructor<? extends BeanFactory> cstr =
      bfc.getConstructor(new Class[]{});
    // The following line causes a warning
    return cstr.newInstance(new Object[]{});
  }

  public class BeanFactory<T extends Bean>{
  }

  public class Bean{
  }
}