Question

I have 2 classes, say A & B:

Class A extends B {
    public void subClassMthd(){
        System.out.println("Hello");
    }
}

Class B {
    public void printHelloWorld {
        System.out.println("Hello");
    }
}

Now, I am using reflection to invoke the methods on Class A. I would also like to invoke the printHelloWorld method present in Class B.

I tried using

Class clazz = Class.forName("com.test.ClassA");
Object classAInstance= clazz.newInstance();
Method superClassmthd = classAInstance.getClass()
    .getSuperclass().getMethod("printHelloWorld", null);
superClassmthd.invoke(classAInstance);

Also tried as

Class clazz = Class.forName("com.test.ClassA");
Object classAInstance= clazz.newInstance();
Class superClazz = Class.forName(classAInstance.getClass().getSuperclass().getName());
Object superclassInstance = superClazz.newInstance();
Method superClassmthd = superclassInstance.getMethod("printHelloWorld", null);
superClassmthd.invoke(superclassInstance );

But none of them work; they throw an InstantiationException.

What am I doing wrong here?

Answer 1

Try this:

Method mthd = classAInstance.getClass().getSuperclass().getDeclaredMethod("XYZ");
mthd.invoke(classAInstance)

The difference is using getDeclaredMethod(), which gets methods of all visibilities (public, protected, package/default and private) instead of getMethod(), which only gets methods with public visibility.