Parent class Subclass Construction method

Extract

A subclass cannot inherit an explicitly defined construction method of a parent class, and if you want to inherit the constructor of the parent class, you need to inherit it by overriding the constructor method and calling the constructor of the parent class in the method by super.

Three case notes:

1. No constructor is explicitly defined in the parent class, at which point there is actually a default parameterless constructor in the parent class. At this point, when you explicitly define any constructed method in a subclass, you can call the default method of the parent class without using super.

2 . The default parameterless construction method is explicitly defined in the parent class, so the subclass can define arbitrary construction methods without having to use super to call the constructor of the parent class .

3, the parent class display defines the construction method , but does not show the definition of the default parameterless construction method , then the subclass definition any constructor method needs to call the parent class by Super constructor method

Parent class Subclass Construction method