查询安装的jdk

[root@VM-24-3-centos ~]# rpm -qa | grep java
java-1.8.0-openjdk-headless-1.8.0.312.b07-1.el7_9.x86_64
tzdata-java-2021e-1.el7.noarch
javapackages-tools-3.4.1-11.el7.noarch
python-javapackages-3.4.1-11.el7.noarch

卸载安装的jdk

[root@VM-24-3-centos ~]# yum -y remove java-1.8.0-openjdk-headless-1.8.0.312.b07-1.el7_9.x86_64

安装openjdk

yum -y install java-1.8.0-openjdk java-1.8.0-openjdk-devel

查看位置

[root@iZm5ee1mp8u5k7ze0hbzzjZ jdk]# dirname $(readlink $(readlink $(which java)))
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.252.b09-2.el7_8.x86_64/jre/bin

设置环境变量

vim /etc/profile.d/env_export.sh

添加如下内容

export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.252.b09-2.el7_8.x86_64
JRE_HOME=$JAVA_HOME/jre
CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
export JAVA_HOME JRE_HOME CLASS_PATH PATH

刷新环境变量

source /etc/profile.d/env_export.sh

查看

java -version

windows openjdk安装
下载地址 http://jdk.java.net/16/

解压后

配置环境变量
PATH E:\install\jdk-16.0.1\bin
JAVA_HOME E:\install\jdk-16.0.1

查看
C:\Users\Administrator>java -version
openjdk version “16.0.1” 2021-04-20
OpenJDK Runtime Environment (build 16.0.1+9-24)
OpenJDK 64-Bit Server VM (build 16.0.1+9-24, mixed mode, sharing)

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