OOP设计原则

What the open–closed principle is, why it is needed, and how to implement it through abstractions, inheritance, composition, and aggregation.

What the Liskov substitution principle is, why it is needed, and how subclasses should preserve the meaning of parent-class behavior.

What the dependency inversion principle is, why it is needed, and implementation guidance centered on interfaces and abstract classes.

What the single responsibility principle is, why it is needed, and how to separate different responsibilities into different classes or modules.

What the interface segregation principle is, why it is needed, and how to keep interfaces small and tailored to their callers.

What the Law of Demeter is, why it is needed, and how to reduce coupling by limiting what objects depend on and expose.

What the composition reuse principle is, why it is needed, and how composition or aggregation can be preferred over inheritance for code reuse.

What object-oriented design principles are, why they are needed, and the main principles covered by these notes.