linux安装jdk
http://www.bookerhome.com/book/101631905710001/content/106949174310001
linux安装java
1.创建文件夹/usr/local/java
2.上传jdk安装包到该文件夹
rz jdk-8u202-linux-x64.tar.gz
3.解压jdk
tar -zxvf jdk-8u202-linux-x64.tar.gz
4.设置环境变量
vim /etc/profile
在 profile 文件中添加如下内容并保存：
#set java environment
JAVA_HOME=/usr/local/java/jdk1.8.0_202
JRE_HOME=/usr/local/java/jdk1.8.0_202/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
vim ~/.bashrc
末尾追加
export JAVA_HOME=/usr/local/java/jdk1.8.0_202
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:$PATH5.让修改生效：
source /etc/profile
6.测试
java -version
安装完毕之后看，如果openjdk为默认的，可按以下操作修改
https://blog.csdn.net/qq_36477176/article/details/123926255
jdk下载地址：
https://www.oracle.com/java/technologies/downloads/
右击要下载的版本，复制链接获取真实免登录下载地址。链接如下，文字加粗部分为 直链下载地址，但是需要登录
https://www.oracle.com/webapps/redirect/signon？nexturl=https://download.oracle.com/otn/java/jdk/8u271-b09/61ae65e088624f5aaa0b1d2d801acb16/jdk-8u271-windows-x64.exe替换直链中，otn为otn-pub，真实直链下载地址为
https://download.oracle.com/otn-pub/java/jdk/8u271-b09/61ae65e088624f5aaa0b1d2d801acb16/jdk-8u271-windows-x64.exe