centos7.9+jdk-8u231 dockerfile实例：

# CentOS with JDK 8
# Author   xx@xx.com

# build a new image with basic  centos
FROM centos:centos7.9.2009
# who is the author
MAINTAINER xx@xx.com

RUN ln -sf /usr/share/zoneinfo/Asia/Shanghai /etc/localtime

# make a new directory to store the jdk files
RUN mkdir /opt/software \
    && yum -y install vim net-tools telnet tree wget curl \
    && yum clean all

# copy the jdk  archive to the image,and it will automaticlly unzip the tar file
ADD jdk-8u231-linux-x64.tar.gz /opt/software

# set environment variables
ENV JAVA_HOME /opt/software/jdk1.8.0_231
ENV JRE_HOME ${JAVA_HOME}/jre
ENV CLASSPATH .:JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
ENV PATH ${JAVA_HOME}/bin:$JRE_HOME/bin:$PATH