JDK multi-version installation Windows and Linux
Multiple versions of jdk are installed on Windows, if adjusting environment variables does not take effect, go directly to the end
Go to the official website to download jdk
The previous official website download address:
https://www.java.com/zh-CN/download/Because
it was acquired by Oracle, now it will go to Oracle to download: https://www.oracle.com/java/technologies/downloads /archive/
All releases can be found on the right, download the required version:
You can download the exe version or the compressed version. You don’t need to install the compressed version. You can directly unzip it to the directory you created to configure the environment variables and skip the next step.
The two installation methods are similar!
Install jdk to this machine
1. Run the installer, the next step is the default, here you can change the default installation location of JDK:
2. Install jre
After the installation of jdk is completed, a dialog box for installing jre will pop up. This jre can also change the installation location. It is recommended to install it in the same parent directory as jdk. Although jre comes with jdk, this jre still needs to be installed.
It can be used after the installation is complete, but it is generally necessary to configure environment variables during development.
set environment variables
1. Enter environment variables
This Computer => Properties => Advanced System Settings => Advanced => Environment Variables
Create a new modification in the system variable! It's the one below! Note that all punctuation marks are in English.
2. New: JAVA_HOME
Variable value: the installed JDK directory
Description: This is convenient for later development and use
3. New: CLASSPATH
Variable value: .;%JAVA_HOME%\lib\dt.jar;%JAVA_HOME%\lib\tools.jar
Description: Paths of various jar packages
4. Edit the path variable value
Find the path, double-click this one to edit:
Create two new
%JAVA_HOME%\bin
%JAVA_HOME%\jre\bin
save!
Be sure to save!
Check installation status
Check whether the Java environment variable is set successfully in cmd
java -version
After reading the version, you can also write a hello word and try it out!
So far, the work is not finished... If you have installed multiple versions, the first method is the same, but the environment variable does not need to be set, but there will be a problem that the environment variable is modified, but the cmd does not take effect, just see the following.
Remark
You can also download the compressed file directly, unzip and configure the environment variables.
Install under Linux
Download the compressed package of the corresponding version, unzip it to the directory you want to install, and configure the environment variable:
modify the /etc/profile file
sudo vim /etc/profile
Shift+g jumps to the end of the file and appends:
JAVA_HOME=安装目录
export JRE_HOME=$JAVA_HAOME/jre
export CLASSPATH=.:$JAVA_HOME/lib:$JRE_HOME/lib
export PATH=$JAVA_HOME/bin:$PATH
Refresh the variables: (restart is also possible)
source /etc/profile
It can be
viewed in the terminal using java -version
Windows multi-version JDK modification of environment variables does not take effect
This is also a common pit. After installing multiple versions of jdk at the same time, it turns out that after modifying the value of JAVA_HOME, it is still the last installed version in cmd. This is because java.exe, javaw.exe, The three javaws.exe files are placed in the system directory, and the priority in the environment variable is higher than that set by ourselves, so it will run here.
C:\ProgramData\Oracle\Java\javapath
或者是
C:\Windows\System32
Mine is in the first path, just delete it (does not affect the normal development and use), should I say nothing, the software Everything is easy to use, and I will have a chance to publish a guide on the use of Everything later.
It will return to normal after deletion.