It doesn't affect 

~ % java -version
java version "17.0.1" 2021-10-19 LTS
Java(TM) SE Runtime Environment (build 17.0.1+12-LTS-39)
Java HotSpot(TM) 64-Bit Server VM (build 17.0.1+12-LTS-39, mixed mode, sharing)

 Output this help message to the error stream 
    --help         Output this help message to the output stream 
    -X             Output help for additional options to the error stream 
    --help-extra   Output the help of additional options to the output stream 
    -ea[:< Package name >...|:< Class name >]
    -enableassertions[:< Package name >...|:< Class name >]
                   Enables assertions at the specified granularity 
    -da[:< Package name >...|:< Class name >]
    -disableassertions[:< Package name >...|:< Class name >]
                   Disables assertions at the specified granularity 
    -esa | -enablesystemassertions
                   Enable system assertion 
    -dsa | -disablesystemassertions
                   Disable system assertions 
    -agentlib:< Library name >[=< option >]
                   Load the native agent Library  < Library name >,  For example  -agentlib:jdwp
                   See also  -agentlib:jdwp=help
    -agentpath:< Pathname >[=< option >]
                   Load the native agent library by full pathname 
    -javaagent:<jar  route >[=< option >]
                   load  Java  Programming language agent ,  see also  java.lang.instrument
    -splash:< Image path >
                   Displays the startup screen using the specified image 
                   Automatic support and use  HiDPI  Zoom image 
                  ( If available ). Unscaled image file names should always be  ( For example , image.ext)
                   Pass as a parameter to  -splash  option .
                   The most appropriate zoom provided will be automatically selected 
                   image .
                   For more information ,  see also  SplashScreen API  file 
    @argument  File 
                   One or more parameter files containing options 
    [email protected]
                   Prevent further expansion of the parameter file 
    --enable-preview
                   Allow classes to rely on the preview capabilities of this release 
 To specify parameters for the long option ,  have access to  --< name >=< value >  or 
--< name > < value >.// Probably so 

 metro 

win+R   enter 
cmd   enter 
 Enter ECHO %path%   enter  
 Can display     'F:\java\bin'  java Directory path · See if it's right 

C:\Program Files\Java\jdk1.8.0_72

Path In  %JAVA_HOME%\bin; route , Bind variable name   by JAVA_HOME of  E:\JDK route 

win7 sure , My old computer was win7 of 

win7 tolerable , Apple macOS The system can also , Install JDK After, you need to configure variables before you can cmd Run in .class File , Otherwise, you can only JDK In Java and Javac Can only be executed under the root directory of , When executing files on the desktop, you should pay attention to whether the path is complete , No, Desktop To add Desktop To execute successfully 

 Step one ： First create a new... On the environment variables page JAVA_HOME variable -------- The address is what you installed JDK Location 
 Step two ： Find... In the system variable below Path Click Edit variable to open the edit environment variable window ----------- Enter %JAVA_HOME%\bin It's solved 
 Step 3 ： inspect JDK Whether the configuration is successful ,windows key +R build   The lower left corner comes out to run the window , Enter cmd Then press enter to enter the command window , Then enter java -version Check if there is version information 

JAV_HOME
PASH

 It is recommended to change the coding format to utf-8,

 There is no need to blindly pursue the latest version , You should choose a stable version , as 1.8.

QQ:2661009083

jdk decompression , Configure the environment variables   Run... In the command line window java Follow javac No display is not an internal or external command jdk It's just installed 

java It's not very difficult , It's relatively easy to learn , Now use Java The majority of people , Personally feel , If different , Please put forward and correct , thank you 

JAVA_HOME="C:\Program Files\Java\jdk1.8.0_65"

// stay windows In the system environment variable , Create a new row 
JAVA_HOME="C:\Program Files\Java\jdk1.8.0_65"

123

 Argus is deeply into the bone marrow. He buys it personally 

eeeee

 You added it in the user variable  ,   So it didn't add successfully . 2  A configuration should be added to the environment variable  .

 no   Put it in E disc 

 Just choose according to the number of bits of the operating system 

 Open dos window , Configure environment variables 
1、 to configure JAVA_HOME
set JAVA_HOME=C:\Program Files\Java\jdk1.8.0_65
2、 to configure path route 
set path=%path%;C:\Program Files\Java\jdk1.8.0_65\bin

public class helloworld {
    public static void main(String[] args)
     {
       /* System.out.println("helloworld");
}

}

 hold JAVA_HMOE The value is set to C:\Program Files\Java\jdk1.8.0_65

public class HelloWord {
	public static void main(String[] arges) {
		System.out.println("helloword!");
	}
}

 For example ：jdk stay H:\jdk, you JAVA_HOME The value of the variable is filled in H:\jdk All right 

 For example ：jdk stay H:\jdk, you JAVA_HOME The value of the variable is filled in H:\jdk All right 

 Variable name ：JAVA_HOME
 Variable value ：C:\Program Files\Java\jdk1.8.0_65
Path：%JAVA_HOME%\bin;
 be careful ： If it is Windows10 system , To write jdk and jre The absolute path of 
Path：C:\Program Files\Java\jre1.8.0_65\bin;C:\Program Files\Java\jdk1.8.0_65\bin;
CLASSPATH：.;%JAVA_HOME%\lib\dt.jar;%JAVA_HOME%\lib\tools.jar;

 Variable name ：JAVA_HOME
 Variable value ：C:\Program Files\Java\jdk1.8.0_65

1. You can put cmd Name the line and try , Try again .
2. If you don't succeed , Check your installation path carefully D:\jdk

 Unzipped jdk Whether the folder is D：\jdk

bin There must be a semicolon behind it ;

1. You can try another browser 
2. If you can't, shut down and restart 

 On the command line, enter java -version, see jdk Information about . You can see your own jdk yes 64 Bit or 32 position 

64 The bit system is compatible 32 Bit .32 Bit incompatibility 64 position .
 Generally speaking, your computer is 64 Bit , you 32 Bit and 64 Multiple bits can be used . If your computer is 32 Bit , You can only use 32 Bit .

WIN10  to configure , The personal test is feasible as follows :
1.
 Variable name ：JAVA_HOME
 Variable value ：E:\JDK
2.
 Create a new environment variable CLASSPATH
 Variable name ：CLASSPATH
 Variable value ：.;%JAVA_HOME%\lib\dt.jar;%JAVA_HOME%\lib\tools.jar
 You need to pay attention to the... In front of the variable value “.;”
3.
 Configure environment variables Path
 double-click Path, Click New , add to “%JAVA_HOME%\bin”;
 Click new again , add to “%JAVA_HOME%\jre\bin”.
 Special attention should be paid here ,win10 The environment variable values are line by line , Don't directly click New , add to “%JAVA_HOME%\bin;%JAVA_HOME%\jre\bin;”, Otherwise, there will be “javac Not internal or external commands ” error .

1. Create a new system variable . Name is JAVA_HOME Then select C:\Program Files\Java\jdk1.8.0_65 catalogue   Click ok .

2. Choose path Click Edit  , Select edit text and add... To the variable value %JAVA_HOME%\bin

 Right click this computer >> attribute >> Advanced system settings >> Environment variables >> User variables --> newly build >> Variable name ：JAVA_HOME --> Variable value ：C:\Program Files\Java\jdk1.8.0_65 >> determine --> newly build >> Variable name ：CLASS_PATH --> Variable value ：C:\Program Files\Java\jdk1.8.0_65\lib >> determine 
 On the command line, enter java -version The version number is the environment variable, and the configuration is correct 

 Turn on the system -> Advanced system settings -> Advanced -> Environment variables -> Edit ( System variables )
1、 Variable name ：JAVA_HOME
       Variable value ：C:\Program Files\Java\jdk1.8.0_65
2、 Variable name ：CLASSPATH
       Variable value ：.;%JAVA_HOME%\lib\dt.jar;%JAVA_HOME%\lib\tools.jar;
3、 Variable name ：Path
       Variable value ：%JAVA_HOME%\bin;%JAVA_HOME%\jre\bin;
 be careful ： If win10, You need to  %JAVA_HOME%\bin;%JAVA_HOME%\jre\bin;  Add... Separately , Otherwise you can't recognize 

 Turn on the system -> Advanced system settings -> Advanced -> Environment variables -> Edit ( System variables )
1、 Variable name ：JAVA_HOME
       Variable value ：C:\Program Files\Java\jdk1.8.0_65
2、 Variable name ：CLASSPATH
       Variable value ：.;%JAVA_HOME%\lib\dt.jar;%JAVA_HOME%\lib\tools.jar;
3、 Variable name ：Path
       Variable value ：%JAVA_HOME%\bin;%JAVA_HOME%\jre\bin;
 be careful ： If win10, You need to  %JAVA_HOME%\bin;%JAVA_HOME%\jre\bin;  Add... Separately , Otherwise you can't recognize 

 same ,windows Case insensitive 

.;%JAVA_HOME%\lib;%JAVA_HOME%\lib\dt.jar;%JAVA_HOME%\lib\tools.jar