安装jdk-7u21：rpm -ivh rpm -ivh jdk-7u21-linux-x64.rpm
安装时出现如下错误，提示文件冲突，表明正在安装的jdk-7u21和已安装的jdk-7u79冲突：
file /etc/init.d/jexec from install of jdk-2000:1.7.0_21-fcs.x86_64 conflicts with file from package jdk-2000:1.7.0_79-fcs.x86_64
查看已安装的jdk：rpm -qa|grep jdk
卸载掉冲突的jdk：rpm -e --nodeps jdk-1.7.0_79-fcs.x86_64
重新安装jdk-7u21 ：rpm -ivh rpm -ivh jdk-7u21-linux-x64.rpm
查看当前安装的jdk：rpm -qa|grep jdk
来源：oschina
链接：https://my.oschina.net/u/1588291/blog/651165