Detailed introduction to java language

1.1 Software Development

1.1.1 Software

• A collection of computer data and instructions organized in a specific order.

• Commonly used software:

• Minesweeper, Thunder, QQ, etc.

• DOS, Windows, Linux, etc.

• System software:

• Application software:

1.1.2 What is Software development?

• Production software

1.2 Human-computer interaction

• Software The emergence enables better interaction between humans and computers.

• Interaction method:

• Graphical interface (GUI): This method is simple and intuitive, easy for users to accept and easy to use operate.

• Command line mode (CLI): You need a console to enter specific instructions to let the computer complete some operations. It is more troublesome and needs to remember some commands.​

#1.3 What is a computer language?

1.3.1 Language

• is a way of communication between people.

• For example: Chinese people use Chinese to communicate with each other, but if Chinese people want to communicate with Korean stickmen, they must learn Korean.

1.3.2 Computer language

• The way people communicate with computers.

• If people want to communicate with computers, they must learn computer language.

• There are many computer languages:

• C

• C++

• java　

• ...

##2 Overview of java language

• is a high-level programming language launched by Sun in 1995.

• is an Internet-oriented programming language.

• As Java technology continues to mature in the web, it has become the preferred development language for web applications.

• is a programming language that is easy to learn, completely object-oriented, safe and reliable, and has nothing to do with the platform.

3 Three technical architectures of java language

• J2EE Enterprise Level

• It is a set of solutions for developing applications in enterprise environments.

• The technologies included in the machine's technical system, such as Servlet and jsp, are mainly aimed at the development of web applications.

• J2SE Standard Edition

• is a solution for developing common desktop and business applications.

• This technology is the basis for the other two and can complete the development of some desktop applications.

• J2ME Small Edition

• is a solution for developing electronic consumer products and embedded devices.

• This technical system is mainly used in small electronic consumer products, such as applications in mobile phones.

4 Characteristics of java language: cross-platform

• Because of the JVM, the same java program can be executed in three different operating systems. In this way, the cross-platform type of Java program is realized, so the Java language has good portability.

5 Java language environment construction

5.1 What are JRE and JDK?

• JRE (java runtime environment)

• Includes the java virtual machine and the core class libraries required for java programs, etc., if To run a developed java program, the computer only needs to install JRE.

• JDK (java development kit)

• JDK is provided to java developers and includes Java development tools also include JRE. So after installing the JDK, there is no need to install the JRE separately.

• The development tools: editing tools (javac), packaging tools (jar), etc.　　

• In short: the java program developed using JDK is handed over to JRE for execution.

6 The first java program

package lesson1;/**
 * 描述：第一个java程序 */public class Demo1 {/** * main()方法 java程序的入口
     * @param args     */public static void main(String[] args) {//输出语句System.out.println("你好啊 java");
    }
}

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