Inheritance order, subclasses overriding methods that inherit from parent class

When constructing an object, the system constructs the parent class object before constructing the subclass object.

Construct the order of an object: (Note: This is also the time to construct the parent class object)

① constructs the parent class object recursively;

② call this class member property to assign the initial value statement sequentially;

③ the construction method of this class.

Super () Represents the constructor method that invokes the parent class.

Super () also must be placed on the first line as this.

This () is used to invoke the constructor method of this class.

If no constructor method is defined, then the parent class's parameterless construction method, super () is called.

Inheritance order, subclasses overriding methods that inherit from parent class