abstract classes and methods, Life, and function binding

This week in OOP we talked about approaches to the Life project, function bindings and how to use non-default bindings in C++/Java, and abstract methods and classes.

When we talk about function binding we are referring to the function that is invoked. The bindings that we have studied this past week are dynamic and static binding, with static binding the declared class of the object/variable is the function that is invoked, with dynamic binding the type of the value that is stored in the variable or the type of the object itself determines the function that is invoked. As you might have guessed by now java uses dynamic function binding by default and C++ uses static by default. However either can have the opposite binding enabled by keywords in Java this is accomplished by the use of private methods, static methods, final methods, or final classes. In C++ dynamic binding is enabled by using the keyword virtual on the parent method, this will cause a look up table to be built and used at runtime to determine the function to be invoked.

Java has the convention that either a class can be abstract and have no abstract methods or it must be abstract if any methods are abstract. As such disallowing instantiation of the class and all subclasses that choose to not implement the abstract methods. If a method is declared abstract then it can’t have an implementation as such you end up having to create protected helper methods if desired with different names. As you might imagine C++ is a slightly different story, you can have abstract(/pure virtual) methods but they may have implementations if you choose to provide them, however the methods must be implemented in function scope. The notion of an abstract class with no abstract methods does not exist in C++ however a pure virtual destructor would give you much the same result.

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