ubuntu20.04中，安装jdk,配置环境变量

1. 下载jdk
   https://www.oracle.com/java/technologies/downloads/

2. 创建目录
   sudo mkdir /usr/lib/jvm

3. 解压缩到该目录
   sudo tar -zxvf jdk-7u60-linux-x64.gz -C /usr/lib/jvm

4. 修改环境变量
   sudo vim ~/.bashrc

   #set oracle jdk environment
   export JAVA_HOME=/usr/lib/jvm/jdk1.8.0_201
   export JRE_HOME=$JAV{A}_{H}OME/jreexportCLASSPATH=.:${JAVA_HOME}/lib:$JR{E}_{H}OME/libexportPATH=${JAVA_HOME}/bin:$PATH

5. 使环境变量马上生效
   source ~/.bashrc