1. Static array, shared by all objects. Just like an air conditioner, once opened, everyone in the room can use it, and once the temperature is changed, the temperature of everyone's feelings changes.
2. The package of the standard class is divided into five parts 1) instance variable 2) constructor 3) SetPoint 4) accessor 5) Functional method
3. The aggregation relationship between classes and classes can greatly increase productivity
4.toString () method system automatic Call
Access to the 5.private modifier the class's access to and modification of the object within that category cannot be obtained and modified by any other class, including subclasses of that class
Public use of the same package or other classes of different packages
Protected the class, the other classes in the same package, the subclasses of the class in the other package use the
Java Basics Course Notes