What does this statement means? I read about virtual functions in C++ , used for run time polymorphism? is it in the same context
The statement is true that java keeps all functions as virtual. During runtime, if a class has function, it will call it otherwise it will look for its base class.
The methods of the class in Java are virtual by default and it’s meaning is same as in the C++ virtual function. To make methods as non-virtual in Java, use final keyword.The programming example can be seen at http://www.geeksforgeeks.org/g-fact-43/
In object-oriented programming, a virtual function or virtual method is a function or method whose behaviour can be overridden within an inheriting class by a function with the same signature to provide the polymorphic behavior.
Therefore according to definition, every non-static method in JAVA is by default virtual method except final and private methods. The methods which cannot be inherited for polymorphic behavior is not a virtual method.