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By default, all methods in all classes are concrete, unless the abstract keyword is used. An abstract class may include abstract methods, which have no implementation. By default, all methods in all interfaces are abstract, unless the default keyword is used. The default keyword can be used to specify a concrete method in an interface.
The concrete factories and products are classes that specialize the abstract classes using inheritance. [4] A more recent structure of the pattern is based on interfaces that define the abstract factory and the abstract products to be created. This design uses native support for interfaces or protocols in mainstream programming languages to ...
By contrast, a concrete class is a class that can be directly instantiated. Instantiation of an abstract class can occur only indirectly, via a concrete subclass. An abstract class is either labeled as such explicitly or it may simply specify abstract methods (or virtual methods).
Abstraction is defined to a concrete (more precise) model of execution. Abstraction may be exact or faithful with respect to a property if one can answer a question about the property equally well on the concrete or abstract model.
In class-based programming, a factory is an abstraction of a constructor of a class, while in prototype-based programming a factory is an abstraction of a prototype object. A constructor is concrete in that it creates objects as instances of one class, and by a specified process (class instantiation), while a factory can create objects by instantiating various classes, or by using other ...
An Abstract Class is a class that is incomplete, or is to be considered incomplete, so cannot be instantiated. A class C has abstract methods if any of the following is true: C explicitly contains a declaration of an abstract method. Any of C's superclasses has an abstract method and C neither declares nor inherits a method that implements it.
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.
Modern object-oriented languages, such as C++ and Java, support a form of abstract data types. When a class is used as a type, it is an abstract type that refers to a hidden representation. In this model, an ADT is typically implemented as a class, and each instance of the ADT is usually an object of that class.