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The Dog class and the Cat class inherit from the Animal class. The Animal class includes a breathe() method and a speak() method. If the speak() method is called from an object of type Dog, the result is a bark. If the speak() method is called from an object of type Cat, the result is a meow.
Which term is used to describe this object-oriented concept?
A. multiple inheritance
B. polymorphism
C. data hiding
D. encapsulation
Correct Answer: B
Explanation/Reference:
Polymorphism is often referred to as the third pillar of object-oriented programming, after encapsulation and inheritance. Polymorphism is a Greek word that means "many-shaped" and it has two distinct aspects:
* At run time, objects of a derived class may be treated as objects of a base class in places such as method parameters and collections or arrays. When this occurs, the object’s declared type is no longer identical to its run-time type.
* Base classes may define and implement virtual methods, and derived classes can override them, which means they provide their own definition and implementation. At run-time, when client code calls the method, the CLR looks up therun-time type of the object, and invokes that override of the virtual method.
Thus in your source code you can call a method on a base class, and cause a derived class’s version of the method to be executed.
