1、查看本地是否自带 java 环境:yum list installed | grep java
    2、删除本地自带的java:yum -y remove java-1.8.0-openjdk
    3、查看仓库的java安装包:yum -y list java

    4、安装java:yum -y install java-1.8.0-openjdk*
    5、查找java安装路径:which java