Java basic knowledge learning notes (1), java learning notes

Java basic knowledge learning notes (1), java learning notes

Understanding object-oriented:

Java's pure object-oriented programming language is represented by three basic features fully supported by Java: inheritance, encapsulation, and polymorphism.

The minimum unit of a Java program isClassClass represents a type of thing with certain characteristics in the objective world. These classes can generate multiple objects in the system, and these objects are directly mapped to various objects in the objective world, the entire Java program is composed of classes.

Structured (claims to step-by-step software by function, for function)/Object-Oriented Programming: (analysis> Design> programming) SA/OOA> SD/OOD> SP/OOP

The smallest program unit in structured programming isFunctionEach function is responsible for completing a function. The entire program is composed of functions. The function serving as the program entry is the main function, and the main function calls other functions in turn, to complete the functions of the entire software system.

Any simple or complex algorithm can be composed of three basic structures: sequence, selection, and cyclic structure.

Unified UML modeling language: a language used for Visual Modeling of software-intensive systems.

UML describes, visualizes, and compiles the products of the object-oriented development system.
A standard language of the document.

The purpose of UML is to describe any type of system in an object-oriented diagram.
Application fields. The most common one is to build a software system model, but it can also be used to describe non-Software
Systems in the field, such as mechanical systems, enterprise organizations or business processes, and information systems that process complex data
Systems, real-time industrial systems or industrial processes. In short, UML is a general standard building
Language used to model any system with static structures and dynamic behaviors.

UML is applicable to the scenarios where the system is tested after the requirement specification is described and the system is completed.
Same stage. In the demand analysis stage, use cases can be used to capture user requirements. Use Case Modeling: Description
External roles interested in the system and their functional requirements for the system (use cases. Questions in the analysis phase
The main concepts (such as abstract, class, and object) and mechanisms in the question domain need to be identified and
The relationships between them are described using UML class diagrams. To implement collaboration between Use Case classes, you can use
UML dynamic model. In the analysis phase, only the objects in the problem domain (concepts in the real world) are modeled,
Classes that do not consider defining technical details in software systems (such as processing user interfaces, databases, communications, and Parallelism)
). These technical details will be introduced in the design phase, so the design phase provides
For more detailed specifications.