The difference between the permissions modifier public, private, protected, and default in Java

1. Public

Classes, member variables, and member functions can be decorated without any restrictions, in the same package, or classes in different packages are free to access

2. Private

member variables and member functions can be decorated and can only be used in this class

3. Default

(Do not write permission modifiers, or default permissions) can be decorated with classes, member variables, and member functions, which are freely accessible in the same package. If the child class and the parent class are not in the same package, the subclass can inherit the member variables and member functions of the default permission in the parent class, but cannot be used because of insufficient permissions

4, Protected

Protected permissions first have the same functionality as default, but this permission only modifies member variables and member functions

5. Inheritance and access rights

(1), if inheritance occurs within the same package:
Subclasses can inherit all the variables of the parent class, but the subclass object can only use the public, protected, default member variables in the parent class, and cannot use the private variable;
(2), if it is a cross-package inheritance:
For the public variable in the parent class, the subclass can be inherited and can be used;
For the protected variable in the parent class, the subclass can be inherited and can be used, but not subclasses are not available;
For the default variable in the parent class, the subclass can inherit and not be used;
For private variables in the parent class, subclasses can inherit and are not available.

The difference between the permissions modifier public, private, protected, and default in Java