1.centos7 默认安装的jdk 

pm -qa | grep java

2.卸载默认的jdk

rpm -e --nodeps tzdata-java-2014i-1.el7.noarch

rpm -e --nodeps java-1.7.0-openjdk-headless-1.7.0.71-2.5.3.1.el7_0.x86_64

3.上传新的jdk

4.解压

tar -zxvf jdk-8u121-linux-x64.tar.gz

5.配环境变量

vi /etc/profile

#set java environment

JAVA_HOME=/usr/jdk1.8.0_121

JRE_HOME=/usr/jdk1.8.0_121/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

6.文件生效

source /etc/profile

7.验证

Java -version