Is it possible to type cast to a parent abstract class?

Question

I'm in the process of porting a C# project into Java. I've got a chunk of code that looks like this:

public abstract class A
{
    public abstract void foo() throws Exception;
    public abstract void bar();
}

And then, elsewhere...

public class FirstOuterClass {
    public class FirstInnerClass extends A {
                  // defines foo() and bar()
    }
}

Further elsewhere...

public class SecondOuterClass {    
     public class SecondInnerClass extends A {
                  // defines foo() and bar()
    }
}

And finally, even MORE elsewhere....

HashMap<Type, A> handlers = new HashMap<Type, A>();
        for (Entry e : HashMapOfStringToEntry.getTypes())
        {       
            if(e.Handler != null) {
                handlers.put(e.Type, (A) e.Handler);
            }
        }

e.Handler can be either a type of FirstInnerClass or SecondInnerClass. It's that conversation e.Handler to (A) that is causing the following error:

java.lang.ClassCastException: java.lang.Class

I've verified with debugging output that e.Handler is indeed a class type of FirstOuterClass$FirstInnerClass. So either there are differences in casting between C# & Java (possible) or I am not providing the right syntax somewhere (also possible).

(I'm sorry for not pasting the whole code, like what the HashMaps are for. I don't want to muddle up the real issue. Basically it's a mapping between a String key and a couple of classes that extend abstract A.)

Answer 1

If one of your inner classes was failing to cast to A, then your exception would look like:

java.lang.ClassCastException: FirstOuterClass$FirstInnerClass cannot be cast to A

Instead, you're getting this:

java.lang.ClassCastException: java.lang.Class

Are you cutting off "cannot be cast to A" at the end of this?

Regardless, it appears that e.Handler is of type java.lang.Class. As in, FirstOuterClass$FirstInnerClass itself rather than a single instance of it.

Answer 2

From the exception message, it appears that you are trying to cast an instance of Class, not an instance of the class it represents.