1、安装JDK1.8

直接使用下面的地址下载java 1.8：

https://repo.huaweicloud.com/java/jdk/8u202-b08/jdk-8u202-linux-x64.tar.gz

2、建立目录，将下载的jdk的安装包复制过去并进行解压

(root㉿Cwillchris)-[~]# sudo mkdir -p /usr/local/java

(root㉿Cwillchris)-[~]# cp jdk-8u202-linux-x64.tar.gz /usr/local/java

(root㉿Cwillchris)-[~]# cd /usr/local/java

(root㉿Cwillchris)-[~]# sudo tar xzvf jdk-8u202-linux-x64.tar.gz

3、配置环境变量（注意下面的版本号要与自己下载的相同）

打开文件/etc/profile

(root㉿Cwillchris)-[~]# sudo vim /etc/profile

添加下列代码到文件中

JAVA_HOME=/usr/local/java/jdk1.8.0_202

PATH=$PATH:$HOME/bin:$JAVA_HOME/bin

export JAVA_HOME

export PATH

4、通知系统Java的位置

(root㉿Cwillchris)-[~]# sudo update-alternatives --install "/usr/bin/java" "java" "/usr/local/java/jdk1.8.0_202/bin/java" 1

(root㉿Cwillchris)-[~]# sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/local/java/jdk1.8.0_202/bin/javac" 1

(root㉿Cwillchris)-[~]# sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/local/java/jdk1.8.0_202/bin/javaws" 1

(root㉿Cwillchris)-[~]# sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/local/java/jdk1.8.0_202/bin/javaws" 1

5、重新载入profile

source /etc/profile

6、切换JDK版本

查看当前版本

(root㉿Cwillchris)-[~]# java -version

openjdk version "11.0.17" 2022-10-18

切换版本

(root㉿Cwillchris)-[~]# update-alternatives --config java

输入2，按回车

再次查看版本

(root㉿Cwillchris)-[~]# java -version

java version "1.8.0_202"