Day5_ sub-class and inheritance

1. Subclass and Parent class

　　　　　　　　Inheritance is a mechanism for creating new classes from existing classes. With inheritance, you can define a generic class of common attributes, and then define subclasses with special attributes based on the generic class, inheriting the properties and behaviors of the generic class, and adding its own new properties and behaviors as needed.

A class derived from inheritance is called a subclass, and the inherited class is called the parent class (Super Class).

Declaring a subclass

In the declaration of a class, define a subclass of a class by using the keyword extends, in the following format:

CALSS Child class Name extends parent class name {

...

}

object is the ancestor class of all classes. Each class (except the object class) has and has only one parent class, and a class can have more than one or 0 subclasses.

Day5_ sub-class and inheritance