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Abstract class and method: description, characteristics and features. What is the difference between an abstract class and an interface

Everyone who has at least minimal programming knowledge wondered why abstract base classes exist. What is their purpose? How to create an abstract class? What benefits do they give in practice? Why are they needed in programming and what features of their implementation must be taken into account?

Abstract classes

abstract class




So in programming they call a unit of program code, on the basis of which objects cannot be created. It should be noted that the heirs of this class may not be abstract. Therefore, the creation of objects based on them is quite possible. If we consider an example from Java, then we will build such a model: we can describe the constructors in class A. But we cannot use them. The way out of this situation is to declare a variable as a reference. Moreover, it is necessary to clearly state that it points to an object of class A. But how can this be done? The ghost will help us with this. It should be borne in mind that the parent class is always considered more universal than the descendant. In many programming languages, cast is used automatically. But if there is no confidence in the existence of such a mechanism, thenyou must explicitly specify a link to the object.





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create an abstract class




There are restrictions on their use. Consider this using the Java programming language as an example . There is such a requirement: if a class has at least one such method, then it must be abstract. And in what cases is it appropriate to use such designs? Let's figure it out with the example of pet classes. To begin with, it should be understood that there is no sound that they all make. Therefore, in the most general class, the implementation of the sound method is not specified. But for him, a body is created that is isolated with the help of blocks. And in the future, when a class of dog, cat or hamster is created, a separate method will be prescribed for him, within which all the features will be revealed.









Interface

what is the difference between an abstract class




Many tools have been created in programming, the purpose of which is to help a person make a good quality product. And within the framework of the topic under consideration, it is necessary to pay attention to this aspect, so that everyone knows the difference between an abstract class and an interface. So, a feature of the latter is that it cannot have properties, and no methods are defined for methods. Exploring the difference between an abstract class and an interface, we should dwell on one more feature. So, the first is inherited, while the second is implemented. To an inexperienced person, this may seem insignificant. But the fact is that only one class can be inherited, and implemented as many as you want. This is the difference between an interface and an abstract class. JavaIt also has the features that exclusively abstract public methods and static constants can be described in it. But at the same time, interfaces can also be inherited. It is necessary to indicate that the operators used are public using public.

Multiple Interface Inheritance

what is the difference between an abstract class and an interface




Such a function is not available for classes in many programming languages ​​(for example, in the Java we are considering). This is due to a number of problems. As such, indicate the ambiguities that arise during inheritance. This was the reason for the introduction of multiple interface inheritance. This partially solves the existing problems, but not all. So, thanks to the principles of encapsulation and polymorphism, interfaces can be successfully implemented in different classes using different methods (although they will have the same name). But do not forget about the existing problems. So, when working with multiple interfaces, you will always have to indicate who we mean. There will also be problems when trying to work with two methods of the same name - in which case they will be impossible to use.Therefore, for such cases it is necessary to take care of the presence of a common implementation.

abstract class and interface




This is a key concept in programming. In this case, abstraction is understood as an independent consideration and separation of the interface and its implementation. Let's look at an example. We have a television that is an object or module. It has an interface. As such, they are means of controlling it, as well as reproducing sound and image. The more advanced the interface is used, the more convenient the TV is in use. We can switch programs by clicking on some buttons. In this case, there is no need to think about the physical processes in the TV. They are taken care of by specialists who assemble the device. We as users are only interested in properties. Returning to programming, we can say that they, by this analogy, are the interface and implementation. Also, if a person is confident in their knowledge,then he can "remove" the lid from our hypothetical TV and improve it. Although this can lead to local success, in most cases the end result is negative. Therefore, programming prohibits access denial and hiding internal components for abstract data. The principle of this mechanism provides for ways to prevent intentional or accidental changes in internal components. And when they talk about abstract data types, they mean their combination with many operations that can be performed on them.The principle of this mechanism provides for ways to prevent intentional or accidental changes in internal components. And when they talk about abstract data types, they mean their combination with many operations that can be performed on them.The principle of this mechanism provides for ways to prevent intentional or accidental changes in internal components. And when they talk about abstract data types, they mean their combination with many operations that can be performed on them.

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abstract base classes




Since programming is based on the construction of a hierarchical tree of relations between objects, the question arises as to whether the properties of the parent code libraries are transferred to the underlying types. Inheritance is understood as a relationship when one person repeats the behavior and structure of something else. In ordinary life, this can be found everywhere. Similar has been carried over to programming regarding abstract elements. As a comparison, we can cite the fact that there is no such organism as a bird. This is an abstract name. As a specific instance, a gull, a nightingale or a sparrow are brought. Due to the presence of inheritance, we can use class libraries, as well as develop them for a specific program. Such a tool allows us to create new objects, simultaneously supplementing or changing the properties of an already created one.The heir receives all the methods and fields of his ancestor and, if necessary, acquires his own attributes. Due to the fact that there are abstract elements and the principle of heritage, there are ample opportunities for modification within the framework of object-oriented programming. In addition, this allows a flexible approach to solving tasks. When inheriting, data and functions are passed to the new class.

difference between an abstract class and an interface




It is necessary in order to apply the same functions to solve different types of tasks. In this case, it is envisaged that it is possible to carry out various actions, the content of which will depend on the type of object with which work is being conducted. By polymorphism we understand the property of elements that have one common parent to perform similar problems in semantic meaning in various ways. Let's draw an analogy with animals. There is such an action - to run. We all understand how it happens. But with different animals (lion, elephant, chimpanzee, crocodile, turtle) this action will be performed in different ways. In this case, the developer is responsible for their movement, which, if necessary, can call a specific subroutine for a particular case by developing an algorithm and successfully implementing it. This is done using a set of methods.In this case, in each individual class, the programmer indicates to which object which properties are inherent. Changing something in the descendants, you can achieve the implementation of certain necessary actions in this case. Such an effect is called polymorphism of objects. In general, an abstract class is an extremely useful programming tool.



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