Single, open and closed, and dependency reversal principles

Single principle:

The single principle is that for a class, there should be only one reason for its change.

 

Principles of openness and closure:

The so-called openness refers to the ease of expansion, and closed refers to the fact that existing changes cannot be modified only for use.

 

Dependency reversal principle:

The principle of dependency inversion means that the top layer does not depend on the lower layer, and all of them only rely on abstraction. In addition, abstraction should not depend on details. Details should depend on abstraction.