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This article mainly shows you the "encapsulation, inheritance, polymorphism in Java", the content is easy to understand, clear, hope to help you solve your doubts, the following let the editor lead you to study and learn "what is the encapsulation, inheritance, polymorphism in Java" this article.

1. Encapsulation

What is encapsulation, talk about your own understanding of encapsulation, encapsulation is to hide the information of the class (such as the properties of the class) inside the class, do not allow external programs to access directly. At this point, we should mention a keyword private, which is a permission modifier that can be used to modify members (variables and methods) to protect members from being used by other classes. If they need to be used by other classes, the corresponding operation needs to be provided: a. Provides the get variable name () method, which is used to get the value b. Provide the set variable name (parameter), which is used to set the value of the member variable, which, like the get method, is decorated with public (and keep in mind that the first letter of the variable name must be capitalized).

two。 Inherit

What is inheritance? talk about your understanding of inheritance. Inheritance is the constant relationship between classes, which is similar to the relationship between inclusion and inclusion in mathematical sets. For example, if college students belong to students, then they can be regarded as college students inheriting the student class. Then the college student class is the subclass of the student class (derivative class), and the student class is the parent class (base class) of the college student class. At the same time, it should be noted that inheritance in Java is single inheritance (multi-level inheritance) and multi-implementation (interface). (it is understood that a class cannot have two fathers, but a son can inherit a father, and a father can inherit a grandfather.)

Format: public class subclass name extends parent class name {}

For example: public class zi extends fu {}

3. Polymorphisms

What is polymorphism, encapsulation and inheritance are almost all prepared for polymorphism. I personally understand that polymorphism is a relationship when java programs use inheritance when running, such as method rewriting. Inheritance is the basis for the implementation of polymorphism.

For example: we can say that college students are college students: college students unst=new college students.

We can also say that college students are students: students st=new college students.

Here college students show different forms at different times. I think this is polymorphism.

The premise and embodiment of polymorphic realization are as follows: 1. There is an inheritance relationship 2. There is a way to rewrite 3. Having a parent class leads to a subclass object

Let's show you the three features of encapsulation, inheritance, and polymorphic java through code.

4. At the end of the code, package Cl1;// first creates an attribute of public class Computer {/ /, the parent class of Computer, encapsulates the properties of the class with the private keyword, and private String name; private int price; / / constructs a parameterless method public Computer () {} / / to construct a parameterized method public Computer (String name) {this.name = name. } / / construct a parameterized method public String getName () {return name;} / / set public void setName (String name) {this.name = name;} / / get public Computer (int price) {this.price = price by adding variable name and initials capitalization through get } / / set public void setPrice (int price) {this.price = price;} / / get public int getPrice () {return price;} / / define parent class study method public void study () {System.out.println ("computer can be used to learn and also type code") by adding variable name and initials capitalization via get and initials capitalization. }} package Cl1;// defines a subclass of Lenovo to inherit the parent class public class Lenovo extends Computer {public Lenovo () {} public Lenovo (String name) {super (name);} / / re-study method, and also inherits and calls the study method public void study () {super.study () in the parent class. System.out.println (getName () + "Price" + getPrice () + "rmb," + "knock on the code, it is not a dream to earn millions a year");}} package Cl1;// creates a subclass of Apple to inherit the Computerpublic class Apple extends Computer {/ / definition make method, while the s object in Computer calls the study method public void make (Computer s) {s.study ();}} package Cl1 / / Test category public class test {public static void main (String [] args) {/ / automatic transformation (upward transition) Computer cp=new Lenovo (); cp.setName ("Lenovo Xiaoxin"); cp.setPrice (5000); / / call the study method cp.study () in Lenovo; / / Polymorphic presentation, Apple apple=new Apple () Apple.make (cp);}}

These are all the contents of the article "what are encapsulation, inheritance and polymorphism in Java?" Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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