Summary of java's six object oriented principles and one principle

1. Single 1 responsibility principle: category 1 does what it should do.

2. Richter substitution principle: a subclass must be able to replace the base class (parent class), otherwise it should not be designed as a subclass.

3. Principle of dependency inversion: design should rely on abstraction rather than concretization.

4. Interface isolation principle: interface should be small and specialized, not large and complete.

5. Open and close principle: a software entity such as a class, module, and function should be open for extension and closed for modification.

6. Composition/aggregation reuse principle: use composition and aggregation as much as possible, and use inheritance relationships as little as possible to achieve reuse principle.

7. Demeter's law: low coupling, high cohesion.