Java Language Overview

1、 Java Basics

2、 Software

1. What is software?

Software = data + instruction [command] + document

2. What does software development mean?

Software development is to create the corresponding software system according to the needs of users Software development is a process, including requirement extraction, requirement analysis, software writing and software testing

3、 People interact with computers

Graphical interface vs command line mode dir MD Rd CD cd/ del exit

Computer language? The software needs to run on the computer and communicate with each other in computer language Computer language refers to the language used by people to communicate with computers

4、 Classification of languages

5、 Java language

1. Java concept

Java is an object - oriented programming language officially launched by sun in 1995 and acquired by Oracle in 2010

2. Three systems of Java

Javase: Standard Edition, mainly the core syntax of Java It can be used to develop some desktop applications Java EE: Enterprise Edition, mainly using java language to develop website projects Usually, some large projects such as government system and banking system are developed in Java language Javame: mini version, mainly using java language to develop mobile applications Common mobile phone development: Android set-top box, etc

3. Characteristics

Object oriented, robust, cross platform (write once, run anywhere) -- JVM

6、 Install JDK and configure path environment variable

Note: JDK JRE JVM

7、 Steps for developing Java programs

格式: public class 类名{

//类体: 其他所有java代码都必须放在类体中
  
}

Description: the class name must usually be the name of the java file

Format of main function:

public static void main(String[] 参数名){

}

Description: 1 As the execution entry of Java program, the main function is written in a fixed format 2. The main function must be written in the class body 3 Other specific code must be in the method body

System.out.print("输出内容");  输出内容
System.out.println("输出内容"); 输出内容,同时输出一个换行符

8、 Frequently asked questions

1. What are the relationships among JDK, JRE and JVM, and what are the main structures of JDK and JRE?

JDK = JRE + java development tools (javac.exe, java.exe, Javadoc. Exe)

JRE = JVM + Java core library

2. Why and how to configure the path environment variable?

Path environment variable: the path to be searched by the windows operating system when executing commands

I hope the java development tools can execute successfully in any file path

JAVA_ Home = directory above bin

path = %JAVA_ HOME%\bin

3. What are the common command operations?

cd、md、del、

4. Create the following classes to run

Create a java file, person java

public Class Person{
    public ststic void main(String[] args){
		System.out.println("张三\n");
    	System.out.println("性别：男");
    	System.out.println("地址：北京中南海");
    }
}

5. Instructions for compiling and running the above code

Compile: javac person java

Running: Java person