Java Classes and objects

1. Access rights for classes

	The same class	Same package	Sub-classes under different packages	Non-subclasses under different packages
Private	√
Default	√	√
Protected	√	√	√
Public	√	√	√	√

2.4 Modifier final static This super

1.final

The modifier base type value cannot be changed;

The modified reference type reference cannot be changed, and the object of the invocation can be changed;

The modification method prevents inheritance modification;

The adornment class blocks inheritance.

2.static

Modifying properties and methods allows a class or method to follow a class without having to rely on an object.

3.this

1. In the class method, represents a reference to the method caller object.

2. In the first sentence of the constructor, the constructor that corresponds to the argument is called.

4.super

The child class maintains a reference to the parent class.

3. Reload vs Rewrite

Overloading: Is the same class, the method name + parameter list is different (parameter type and order);

Rewriting: The abortion relationship between the parent class and the subclass;

Subclasses inherit the parent class, which can be overridden, but the method name, parameter list, and return value need to be the same;

Child, the child class modifier cannot be less than the parent class. (The parent class would have public a method, but the subclass becomes private and destroys the consistency)

Java Classes and objects