Ubuntu Install Oracle JDK 8

1. 下载 jdk-8u251-linux-x64.tar.gz

2. 解压到/opt/jdk

   sudo mkdir  -p /opt/jdk
   

3. Install Oracle Java 8 on Ubuntu 20.04 LTS with Alternatives

   sudo update-alternatives --install /usr/bin/java java /opt/jdk/jdk1.8.0_251/bin/java 100
   

4. 如果有多个版本可以这么切换

   sudo update-alternatives --config java
   

5. 配置环境变量

编辑 /etc/environment ，填入以下内容

JAVA_HOME=/opt/jdk/jdk1.8.0_251
JRE_HOME=/opt/jdk/jdk1.8.0_251/jre

使生效

source /etc/environment