Object-oriented principles
1. Single principle
2. The principle of substitution
The essence is inheritance and polymorphism, inheritance or implementation class can replace the parent class
3. Rely on the principle of inversion
The essence is interface-oriented (abstract class) programming
4. Opening and closing principle
Open to expansion, closed to modification
How to achieve the essence is also oriented to abstract programming
5. Interface isolation
The interface needs to be disassembled fine enough
6. Dimit principle
A class should know the least about the objects it calls.
