01.Java Basics - Encapsulation
Basic concepts
Java object-oriented has three major features: Encapsulation, inheritance, and polymorphism. Encapsulation and inheritance basically serve polymorphism.
Encapsulation (Encapsulation): It is to combine the properties and operations (or services) of the object into an independent whole, and hide the implementation details inside the object as much as possible. In layman's terms, it means privatizing the member variables of the class and providing public methods to access these member variables.
Data hiding: If a member variable is declared as a private member, then it cannot be directly accessed through the external class, thus hiding the member variable inside the class. For this reason, encapsulation is also called data hiding.
JavaBean
JavaBean is a specification that stipulates a good encapsulation specification. As long as the class conforms to the specification, it is called a JavaBean.
It has the following characteristics:
Data members (object members) must be modified by private.
Provide public setter/getter methods for each object member
The prototype of the setter/getter must be:
public void set 成员名(成员类型 arg);public 成员类型 get 成员名();
Example study
1. Unencapsulated & Encapsulated
First let’s look at the unencapsulated Member variables:
class Person{ // 将成员的访问权限设置为 public,这也为意味这谁都访问到它 public String name; public int age; }public class Test{ public static void main(String[] args) { Person person = new Person(); //通过类,我们可以直接操作成员变量 person.name ="kobe"; person.age =1000; //直接获得成员变量的值 System.out.println(person.name+"-"+person.age); } }
Let’s encapsulate the above class:
class Person { //1.将成员变量私有化,这样一来外部就不能直接访问到它们 private String name; private int age; //2.提供公共的方法来操作成员变量 public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } }public class Test { public static void main(String[] args) { Person person = new Person(); // 不能直接访问成员变量,而是通过提供的公共方法来设置/获取成员变量的值 person.setName("kobe"); person.setAge(1000); System.out.println(person.getName() + "-" + person.getAge()); } }
So far we have seen the general difference between encapsulated and unencapsulated objects:
For unencapsulated objects, we directly access/set their member variables
And for encapsulated objects, we need to operate members through the provided public methods (such as getters/setters) Variables
2.Encapsulation control object
If it is just like this, encapsulation seems to have no effect. Let’s take a look next How to control objects through encapsulation:
class Person { private String name; private int age; private int city; //对于 name 的控制,直接取消了 setter 方法,这样外部只能访问,而不能设置 name 的值 public String getName() { // 直接返回值 return "kobe"; } public int getAge() { return age; } // 有两个 setter 方法,可以接收 int,String 类型的参数 public void setAge(int age) { this.age = age; } public void setAge(String age) { // 对参数值进行验证,默认只能输入数字 if(age.matches("[0-9]")){ this.age = Integer.valueOf(age); }else{ System.out.println("Error:年龄只能为数字"); } } // 在日常开发,我们一般会将文字转换成编码在数据库存储,因此在存储调用时就要做转换 public String getCity() { switch (city) { case 001: return "北京"; default: return "上海"; } } public void setCity(String city) { if("北京".equals(city)){ this.city = 001; }else if("上海".equals(city)){ this.city = 002; }else{ System.out.println("Error:没有找到该城市"); } } }public class Test { public static void main(String[] args) { Person person = new Person(); person.setAge("a"); //Error:年龄只能为数字 person.setAge(1000); //既可以接收 String 类型,也可以接收 int 类型 person.setCity("广州"); //Error:没有找到该城市 person.setCity("北京"); //此时已经被转换成 001 存储了 //在访问 city 成员变量时,001 又被转换成 北京 显示 System.out.println(person.getName()+"-"+person.getAge()+"-"+person.getCity()); } }
Through the above code, we can roughly summarize the role of encapsulation:
Good encapsulation can reduce coupling.
The structure inside the class can be modified freely.
Can have more precise control over members.
Hide information and implement details.
Reference
The above is the content of 01.Java Basics - Encapsulation. For more related content, please pay attention to the PHP Chinese website (www.php.cn)!
Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

Java 8 introduces the Stream API, providing a powerful and expressive way to process data collections. However, a common question when using Stream is: How to break or return from a forEach operation? Traditional loops allow for early interruption or return, but Stream's forEach method does not directly support this method. This article will explain the reasons and explore alternative methods for implementing premature termination in Stream processing systems. Further reading: Java Stream API improvements Understand Stream forEach The forEach method is a terminal operation that performs one operation on each element in the Stream. Its design intention is

PHP is a scripting language widely used on the server side, especially suitable for web development. 1.PHP can embed HTML, process HTTP requests and responses, and supports a variety of databases. 2.PHP is used to generate dynamic web content, process form data, access databases, etc., with strong community support and open source resources. 3. PHP is an interpreted language, and the execution process includes lexical analysis, grammatical analysis, compilation and execution. 4.PHP can be combined with MySQL for advanced applications such as user registration systems. 5. When debugging PHP, you can use functions such as error_reporting() and var_dump(). 6. Optimize PHP code to use caching mechanisms, optimize database queries and use built-in functions. 7

PHP and Python each have their own advantages, and the choice should be based on project requirements. 1.PHP is suitable for web development, with simple syntax and high execution efficiency. 2. Python is suitable for data science and machine learning, with concise syntax and rich libraries.

PHP is suitable for web development, especially in rapid development and processing dynamic content, but is not good at data science and enterprise-level applications. Compared with Python, PHP has more advantages in web development, but is not as good as Python in the field of data science; compared with Java, PHP performs worse in enterprise-level applications, but is more flexible in web development; compared with JavaScript, PHP is more concise in back-end development, but is not as good as JavaScript in front-end development.

PHP and Python each have their own advantages and are suitable for different scenarios. 1.PHP is suitable for web development and provides built-in web servers and rich function libraries. 2. Python is suitable for data science and machine learning, with concise syntax and a powerful standard library. When choosing, it should be decided based on project requirements.

Capsules are three-dimensional geometric figures, composed of a cylinder and a hemisphere at both ends. The volume of the capsule can be calculated by adding the volume of the cylinder and the volume of the hemisphere at both ends. This tutorial will discuss how to calculate the volume of a given capsule in Java using different methods. Capsule volume formula The formula for capsule volume is as follows: Capsule volume = Cylindrical volume Volume Two hemisphere volume in, r: The radius of the hemisphere. h: The height of the cylinder (excluding the hemisphere). Example 1 enter Radius = 5 units Height = 10 units Output Volume = 1570.8 cubic units explain Calculate volume using formula: Volume = π × r2 × h (4

The reasons why PHP is the preferred technology stack for many websites include its ease of use, strong community support, and widespread use. 1) Easy to learn and use, suitable for beginners. 2) Have a huge developer community and rich resources. 3) Widely used in WordPress, Drupal and other platforms. 4) Integrate tightly with web servers to simplify development deployment.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip
