在CentOS8上使用 yum 安装jdk1.8，环境变量会自动配置好，不需要再手动配置。
查看是否已安装jdk
输入以下命令查看系统是否自带jdk
[root@ecs-s3-medium-2-linux-20200612232105 ~]# rpm -qa |grep java
[root@ecs-s3-medium-2-linux-20200612232105 ~]# rpm -qa |grep jdk
[root@ecs-s3-medium-2-linux-20200612232105 ~]# rpm -qa |grep gcj
如果有输出信息就使用批量卸载命令
[root@ecs-s3-medium-2-linux-20200612232105 ~]# rpm -qa | grep java | xargs rpm -e --nodeps
查看jdk1.8最新版本
[root@ecs-s3-medium-2-linux-20200612232105 ~]# yum list java-1.8*
CentOS-8 - AppStream 6.6 kB/s | 4.3 kB 00:00
CentOS-8 - Base 8.4 kB/s | 3.9 kB 00:00
CentOS-8 - Extras 1.9 kB/s | 1.5 kB 00:00
Extra Packages for Enterprise Linux Modular 8 - x86_64 11 kB/s | 8.1 kB 00:00
Extra Packages for Enterprise Linux 8 - x86_64 15 kB/s | 9.1 kB 00:00
Available Packages
java-1.8.0-openjdk.x86_64 1:1.8.0.252.b09-3.el8_2 AppStream
java-1.8.0-openjdk-accessibility.x86_64 1:1.8.0.252.b09-3.el8_2 AppStream
java-1.8.0-openjdk-demo.x86_64 1:1.8.0.252.b09-3.el8_2 AppStream
java-1.8.0-openjdk-devel.x86_64 1:1.8.0.252.b09-3.el8_2 AppStream
java-1.8.0-openjdk-headless.x86_64 1:1.8.0.252.b09-3.el8_2 AppStream
java-1.8.0-openjdk-javadoc.noarch 1:1.8.0.252.b09-3.el8_2 AppStream
java-1.8.0-openjdk-javadoc-zip.noarch 1:1.8.0.252.b09-3.el8_2 AppStream
java-1.8.0-openjdk-src.x86_64 1:1.8.0.252.b09-3.el8_2 AppStrea
安装jdk1.8
[root@ecs-s3-medium-2-linux-20200612232105 ~]# yum install java-1.8.0-openjdk.x86_64 -y
输入以上命令安装jdk，安装完成后查看jdk版本
[root@ecs-s3-medium-2-linux-20200612232105 ~]# java -version
openjdk version "1.8.0_252"
OpenJDK Runtime Environment (build 1.8.0_252-b09)
OpenJDK 64-Bit Server VM (build 25.252-b09, mixed mode)
卸载
[root@ecs-s3-medium-2-linux-20200612232105 ~]# yum -y remove java-1.8.0-openjdk.x86_64
