"Crazy Java Learning Notes" "Understanding Object Oriented"

"Learning Notes"
1. The Java language is a purely object-oriented language, which is embodied in Java fully supports the three basic features of object-oriented: encapsulation, inheritance, polymorphism. Abstraction is also an important part of object-oriented, but it is not one of the object-oriented features, because all programming languages require abstraction.

2. Object-oriented development method The advantage of a structured development approach is that it provides better reusability, scalability, and maintainability.

3. Object-based and object-oriented differences: Object-based objects are also used, but it is not possible to generate new object types from existing objects as templates, resulting in new objects, i.e., object-based without inheritance. While object-oriented has inheritance, polymorphism is based on inheritance, so the three basic features of object-oriented are indispensable. For example, the JavaScript language is object-based, it uses some encapsulated objects, but it cannot generate new objects.

4, OOA, OOD, OOP are the three processes of OO, and the results of OOA and OOD are recorded using UML language.

5. In the Java language, everything is an object except for 8 basic data types. So Java is a highly object-oriented language, but not a fully object-oriented language.

6, the objective world of the class has a certain structural relationship, usually there are the following 2 kinds: general---special relationship (is a); overall--part relationship (has a)

"Crazy Java Learning Notes" "Understanding Object Oriented"