Question

I’ve a simple generic class follows which accepts a generic type parameter, which is the same as the one declared as a type parameter of the class:

import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Method;

public abstract class SimpleClass<T extends AnnotatedElement>
{

   public void operate()
   {
      Method m = null;
      this.doSomething(m); // Error : SimpleClass.java:[34,10] doSomething(T) in SimpleClass<T> cannot be applied to (java.lang.reflect.Method)
   }
   protected abstract void doSomething(T annotatedElement);
}

This code fails to compile at the following line:

this.doSomething(m); 

with this error:

Error : SimpleClass.java:[34,10] doSomething(T) in SimpleClass<T> cannot be applied to (java.lang.reflect.Method)

Am I missing something here? The type parameter T is marked as T extends AnnotatedElement. As such, I would expect the call to doSomething with a java.lang.reflect.Method argument to compile successfully.

Answer 1

Method implements AnnotatedElement, but that doesn’t require that T is a method. What if the class is declared as SimpleClass<Constructor>? That satisfies <T extends AnnotatedElement>, but doesn’t support conversion from Method.