jdk">1、查询系统中是否已经安装jdk
rpm -qa |grep java
或 rpm -qa |grep jdk
jdk">2、卸载已有的openjdk
rpm -e --nodeps java-1.7.0-openjdk
rpm -e --nodeps java-1.7.0-openjdk-headless
rpm -e --nodeps java-1.8.0-openjdk
rpm -e --nodeps java-1.8.0-openjdk-headless
jdk18">3、安装jdk1.8