1.卸载旧版本

# 查看系统是否自带 jdk
rpm -qa |grep java
rpm -qa |grep jdk
rpm -qa |grep gcj

# 如果有输出信息，批量卸载系统自带
rpm -qa | grep java | xargs rpm -e --nodeps

# 如果使用 yum 安装的 jdk，请使用下面命令卸载
yum -y remove java-1.8.0-openjdk-headless.x86_64

2.安装JDK

# 检查 yum 中有没有 java1.8 包
$ yum list java-1.8*

java-1.8.0-openjdk.x86_64                                              1:1.8.0.272.b10-3.el8_3                                AppStream
java-1.8.0-openjdk-accessibility.x86_64                                1:1.8.0.272.b10-3.el8_3                                AppStream
java-1.8.0-openjdk-demo.x86_64                                         1:1.8.0.272.b10-3.el8_3                                AppStream
java-1.8.0-openjdk-devel.x86_64                                        1:1.8.0.272.b10-3.el8_3                                AppStream
java-1.8.0-openjdk-headless.x86_64                                     1:1.8.0.272.b10-3.el8_3                                AppStream
java-1.8.0-openjdk-javadoc.noarch                                      1:1.8.0.272.b10-3.el8_3                                AppStream
java-1.8.0-openjdk-javadoc-zip.noarch                                  1:1.8.0.272.b10-3.el8_3                                AppStream
java-1.8.0-openjdk-src.x86_64                                          1:1.8.0.272.b10-3.el8_3                                AppStream

# 开始安装
yum install java-1.8.0-openjdk* -y

3.验证

# jdk的默认安装位置为/usr/lib/jvm

[root@localhost ~]# java -version
openjdk version "1.8.0_222"
OpenJDK Runtime Environment (build 1.8.0_222-b10)
OpenJDK 64-Bit Server VM (build 25.222-b10, mixed mode)

4.配置环境变量

# 查看安装的jdk路径
cd /usr/lib/jvm/

# 配置
vi /etc/profile

# java
export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.282.b08-1.el7_9.x86_64
export CLASSPATH=.:${JAVA_HOME}/jre/lib/rt.jar:${JAVA_HOME}/lib/dt.jar:${JAVA_HOME}/lib/tools.jar
export PATH=$PATH:${JAVA_HOME}/bin

# 保存并退出
:wq

# 配置文件生效
source /etc/profile