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小高分享（54）Java中的super关键字和final关键字

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Xiao Gao shares (54) the super keyword and final keyword in Java

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1. super关键字详解

1. Description of the super keyword

（1）继承的魅力：super关键字用于表示父类（超类）的引用。在继承关系中，子类可以通过super关键字调用父类的方法和属性。

(1) The charm of inheritance: The super keyword is used to represent a reference to the parent class (superclass). In an inheritance relationship, a subclass can invoke the methods and properties of its parent class with the super keyword.

（2）调用父类构造方法：在子类的构造方法中，使用super()可以调用父类的构造方法。如果不显式调用，Java默认会在子类构造方法的第一行调用父类的无参构造方法。

(2) Call the superclass constructor: In the constructor of the subclass, use super() to call the constructor of the superclass. If not explicitly called, Java defaults to calling the parent class's parameterless constructor on the first line of the subclass constructor.

（3）解决同名问题：当子类和父类中存在同名方法或属性时，使用super关键字可以明确指出调用的是父类的方法或属性，避免混淆。

(3) Solve the problem of the same name: when there are methods or attributes of the same name in the subclass and the parent class, the super keyword can clearly indicate that the method or attribute of the parent class is called to avoid confusion.

（4）super与this的区别：super用于指向父类，而this指向当前对象。在构造方法中，super()和this()都不能同时出现，因为它们都必须位于第一行。

(4) The difference between super and this: super is used to point to the parent class, while this refers to the current object. In a constructor, neither super() nor this() can appear together, because they must both be on the first line.

2. final关键字详解

2. Description of the final keyword

（1）不可更改的类：使用final修饰的类称为最终类，不能被其他类继承。例如，Java中的String类就是一个最终类，保证了字符串操作的安全性。

(1) Unalterable classes: Classes that use final are called final classes and cannot be inherited by other classes. For example, the String class in Java is a final class that guarantees the security of string operations.

（2）不可重写的方法：final修饰的方法称为最终方法，不能被子类重写。这有助于保证方法的行为在继承体系中保持不变。

(2) Non-overridden methods: final modified methods are called final methods and cannot be overridden by subclasses. This helps ensure that the behavior of the method remains unchanged in the inheritance system.

（3）常量定义：final修饰的变量称为常量，其值一旦赋值，就不能更改。常量名通常使用全大写字母表示，如：public static final int MAX_VALUE = 100；

(3) Constant definition: The final variable is called a constant, and its value cannot be changed once it is assigned. Constant names are usually represented in all uppercase letters, for example: public static final int MAX_VALUE = 100;

（4）提高性能：在Java中，使用final关键字可以提升性能。编译器会尝试内联所有final方法，减少方法调用的开销。

(4) Improve performance: In Java, using the final keyword can improve performance. The compiler attempts to inline all final methods, reducing the overhead of method calls.

（5）final与static结合：final和static关键字可以一起使用，表示一个类的常量，即静态常量。例如：public static final int PI = 3.14159;

(5) final combined with static: The final and static keywords can be used together to represent a constant of a class, that is, a static constant. For example, public static final int PI = 3.14159;

3. super与final的应用

3. super and final applications

（1）在继承关系中，合理使用super关键字，可以更好地复用父类的代码，提高开发效率。

(1) In the inheritance relationship, the rational use of the super keyword can better reuse the code of the parent class and improve development efficiency.

（2）在设计类时，考虑使用final关键字，确保类的安全性。例如，将工具类设置为final，防止他人意外继承。

(2) When designing the class, consider using the final keyword to ensure the security of the class. For example, setting the tool class to final prevents others from accidentally inheriting it.

（3）在方法设计上，使用final关键字可以避免子类修改方法的行为，保证方法的稳定性。

(3) In method design, using the final keyword can avoid the behavior of subclasses to modify the method and ensure the stability of the method.

（4）利用final变量定义常量，提高代码的可读性和可维护性。

(4) Use final variables to define constants to improve the readability and maintainability of the code.

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