window

#配置环境变量
CLASSPATH
.;%JAVA_HOME%\lib;%JAVA_HOME%\lib\tools.jar

JAVA_HOME
D:\Software\Java_jdk\jdk

Path
;%JAVA_HOME%\bin;%JAVA_HOME%\jre\bin;

Linux

$sudo tar -zxvf jdk-8u161-linux-x64.tar.gz -C /usr/java
$sudo vi /etc/profile

JAVA_HOME=/usr/java/jdk1.8.0_161
CLASSPATH=.:$JAVA_HOME/lib:$CLASSPATH
PATH=$JAVA_HOME/bin:$PATH
export JAVA_HOME   CLASSPATH   PATH

#更新环境变量
$source /etc/profile
#查看是否安装成功
$java -version