What are the access rights of class members?

There are 4 types of access permissions for Java class members, namely: 1. package (access within the package); 2. private (access within the class); 3. public (access across packages); 4. protected ( Classes in the package are inherited and reused by classes outside the package).

The operating environment of this tutorial: Windows 7 system, Java 10 version, Dell G3 computer.

There are four access control characters in Java.
Scope Current class The same package Descendants classes Other packages
public √ √ √ √ √ √
protected √                                    
friendly                                                       
private √ √                                              

If not, the default is friendly, such as constructors, etc.~

There are 4 access modifiers in the Java language: package (default), private, public and protected.

1. Package is the default protection mode, also called package access. This protection mode is used when there are no modifiers. Package access allows fields and methods to be accessed by any method of any class within the same package. (In-package access)

2. The access mode of the private identifier indicates that private fields and methods can only be accessed by other methods in the same class, realizing data hiding; when necessary, private variables can be accessed through methods. (Intra-class access)

3. The public modifier is used to expose fields and methods so that they can be accessed outside the package in which the class is defined. This level is also required for necessary interface elements in packages and classes; the main() method must be public, and the toString() method must also be public. Generally, you will not expose a field using public unless the field has been declared final. (Cross-package access)

4. The protected modifier provides a way to access the package (with restrictions) from outside the package. Adding the protected modifier before fields and methods will not affect their access by other classes and methods in the same package. To access a package (a class containing protected members) from outside the package, you must ensure that the class being accessed is a subclass of the class with protected members. In other words, you can use this level when you want a class in the package to be inherited and reused by classes outside the package. Generally should be used with caution. (Classes in the package are inherited and reused by classes outside the package)

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