The six principles of object-oriented transformation, and the six principles of object-oriented
Six principles of object-oriented:
Single responsibility principle, open and closed principle, internal conversion principle, dependency inversion principle, interface isolation principle, And Demeter Principle
Implicit conversion principle:
I have summarized the following two points:
1. Subclass objects can be implicitly converted to parent objects. 2. If the parent class object has a subclass constructor instantiated, this parent class object can be forcibly converted to this subclass object. The "is" and "as" keywords are used for forced conversion. The difference is as follows: is: if the conversion is successful, true is returned, and false is returned if the conversion fails. as: If the conversion is successful, the corresponding object is returned, return null for failure.