首先去官方站点下载java源码包
http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html

解压
tar -zxf jdk-8u181-linux-x64.tar.gz
设置环境变量
[root@java jdk1.8]# vim /etc/profile
JAVA_HOME=/usr/local/java/jdk1.8
JRE_HOME=$JAVA_HOME/jre
PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
export JAVA_HOME JRE_HOME PATH CLASSPATH
使环境变量生效
[root@java jdk1.8]# source /etc/profile
检查java版本
[root@java jdk1.8]# java -version
java version "1.8.0_181"
Java(TM) SE Runtime Environment (build 1.8.0_181-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.181-b13, mixed mode)