From wikipedia In Java, all non-static methods are by default “virtual functions.” Only methods marked with the keyword final, which cannot be overridden, along with private methods, which are not inherited, are non-virtual.
Your SortedContainerImpl class has two separate Container base classes. One is virtual (via the SortedContainer class) and the other is non-virtual (via the ContainerImpl class). SortedContainerImpl has concrete implementations of Container::get_size() and Container::get(int) for the base that comes in from ContainerImpl, but not for the virtual base that comes in via SortedContainer. One way to … Read more
They can result if you try to make a virtual function call from a constructor or destructor. Since you can’t make a virtual function call from a constructor or destructor (the derived class object hasn’t been constructed or has already been destroyed), it calls the base class version, which in the case of a pure … Read more
Virtual methods have an implementation and provide the derived classes with the option of overriding it. Abstract methods do not provide an implementation and force the derived classes to override the method. So, abstract methods have no actual code in them, and subclasses HAVE TO override the method. Virtual methods can have code, which is … Read more
Here is how I understood not just what virtual functions are, but why they’re required: Let’s say you have these two classes: In your main function: So far so good, right? Animals eat generic food, cats eat rats, all without virtual. Let’s change it a little now so that eat() is called via an intermediate function (a trivial function just … Read more