Enthuware

A x = new --> B() <--; B y = new --> B() <--; B z = new --> C() <-- ;

In this case, x.mB() is invalid call. It will not even compile because the class of x is A, which does not contain method mB().

crux terminatus wrote:I'm having a hard time understanding the explanation for this one.

Fundamentally, here is how I understand polymorphism:

Type varname = new Class();

When the program is run, the compiler will, when trying to determine which method(s) it can run, look at the right (Class()), not at the left (type).

winddd wrote:"A Polymorphic call means that irrespective of the type of the variable, the method of the actual class of the object referred by the variable is invoked." - yes. "In java, all non-private method calls are polymorphic because which method is invoked is decided at runtime based on the class of the object instead of compile time." - no. In java, all non-private methods are VIRTUAL. No any polymorphism in call var.mB() for B b = new C();

The Java virtual machine (JVM) calls the appropriate method for the object that is referred to in each variable. It does not call the method that is defined by the variable's type. This behavior is referred to as virtual method invocation and demonstrates an aspect of the important polymorphism features in the Java language.

class A{
public void mA(){ };
}

class B extends A {
public void mA(){ }
public void mB() { }
}

class C extends B {
public void mC(){ }
}
and the following declarations:
A x = new B(); B y = new B(); B z = new C();
Which of the following calls are virtual calls?