信息来源链接：

http://www.linuxidc.com/Linux/2016-09/134941.htm
http://blog.csdn.net/testcs_dn/article/details/39026213
https://zhidao.baidu.com/question/265772073.html
http://www.jb51.net/LINUXjishu/150570.html

安装

# 从oracle官网下载你需要的版本JDK的rpm文件
# 通过rpm命令安装jdk
rpm -ivh jdk-8u121-linux-x64.rpm

[root@iZ28nvy56w8Z ~]# rpm -ivh jdk-8u121-linux-x64.rpm\?AuthParam\=1492323051_47a487993c898f2155bfccc2860571b2 
Preparing...                ########################################### [100%]
   1:jdk1.8.0_121           ########################################### [100%]
Unpacking JAR files...
    tools.jar...
    plugin.jar...
    javaws.jar...
    deploy.jar...
    rt.jar...
    jsse.jar...
    charsets.jar...
    localedata.jar...

问题解决

# 安装时无法安装有冲突
# 通过yum命令查询已安装信息
yum list installed

[root@iZ28nvy56w8Z ~]# yum list installed|grep jdk
jdk1.8.0_121.x86_64 2000:1.8.0_121-fcs  installed

# 卸载之前安装信息
yum -y remove jdk1.8.0_121.i586

[root@iZ28nvy56w8Z ~]# yum -y remove jdk1.8.0_121.i586
Loaded plugins: security
Setting up Remove Process
Resolving Dependencies
--> Running transaction check
---> Package jdk1.8.0_121.i586 2000:1.8.0_121-fcs will be erased
--> Finished Dependency Resolution

Dependencies Resolved

=====================================================================================================================================
 Package                         Arch                    Version                                  Repository                    Size
=====================================================================================================================================
Removing:
 jdk1.8.0_121                    i586                    2000:1.8.0_121-fcs                       installed                    266 M

Transaction Summary
=====================================================================================================================================
Remove        1 Package(s)

Installed size: 266 M
Downloading Packages:
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Warning: RPMDB altered outside of yum.
  Erasing    : 2000:jdk1.8.0_121-1.8.0_121-fcs.i586                                                                              1/1 
  Verifying  : 2000:jdk1.8.0_121-1.8.0_121-fcs.i586                                                                              1/1 

Removed:
  jdk1.8.0_121.i586 2000:1.8.0_121-fcs                                                                                               

Complete!

配置环境变量

# 设置JDK目录软链接
ln -s jdk1.8.0_121 currentjdk
# 修改系统环境变量/etc/profile，加入以下信息
# Java environment
JAVA_HOME=/usr/java/currentjdk
JRE_HOME=/usr/java/currentjdk/jre
CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
export JAVA_HOME JRE_HOME CLASS_PATH PATH

# 通过source命令使修改生效
source /etc/profile

查看JDK安装信息

# 查看Java版本
java -version

[root@iZ28nvy56w8Z jre]# java -version
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)

# 查看javac版本
javac -version

[root@iZ28nvy56w8Z jre]# javac -version
javac 1.8.0_121