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There are methods that a subclass cannot override. For example, in Java, a method that is declared final in the super class cannot be overridden. Methods that are declared private or static cannot be overridden either because they are implicitly final. It is also impossible for a class that is declared final to become a super class. [9]
Now if the equals method is called for a Button object and there is no such method in the Button class but there is an overridden equals method in Rectangle or Clickable (or both), which method should be eventually called? It is called the "diamond problem" because of the shape of the class inheritance diagram in this situation.
The non-virtual interface pattern (NVI) controls how methods in a base class are overridden. Such methods may be called by clients and overridable methods with core functionality. [1] It is a pattern that is strongly related to the template method pattern. The NVI pattern recognizes the benefits of a non-abstract method invoking the subordinate ...
For instance, in C#, the base method or property can only be overridden in a subclass if it is marked with the virtual, abstract, or override modifier, while in programming languages such as Java, different methods can be called to override other methods. [15] An alternative to overriding is hiding the inherited code.
Method overloading, on the other hand, refers to differentiating the code used to handle a message based on the parameters of the method. If one views the receiving object as the first parameter in any method then overriding is just a special case of overloading where the selection is based only on the first argument.
In object-oriented programming, the factory method pattern is a design pattern that uses factory methods to deal with the problem of creating objects without having to specify their exact classes. Rather than by calling a constructor , this is accomplished by invoking a factory method to create an object.
D provides an explicit "alias this" declaration within a type can forward into it every method and member of another contained type. [11] Dart provides mixins with default implementations that can be shared. Go type embedding avoids the need for forwarding methods. [12] Java provides default interface methods since version 8.
Java, C++ (Since C++11) and D allow inheritance or overriding a class method to be prohibited by labeling a declaration of a class or method, respectively, with the keyword "final". In the book Effective Java, author Joshua Bloch writes (in item 17) that programmers should "Design and document for inheritance or else prohibit it".