官网下载

地址: http://www.oracle.com/technetwork/articles/javase/index-jsp-138363.html，并选择相应的 .gz 包下载

下载解压都安装目录

sudo tar -zxvf jdk-8u144-linux-x64.tar.gz -C /opt/

设置环境变量

#set oracle jdk environment
export JAVA_HOME=/opt/jdk1.8.0_144 
export JRE_HOME=${JAVA_HOME}/jre  
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib  
export PATH=${JAVA_HOME}/bin:$PATH

设置系统默认jdk 版本

sudo update-alternatives --install /usr/bin/java java /opt/jdk1.8.0_144/bin/java 300  
sudo update-alternatives --install /usr/bin/javac javac /opt/jdk1.8.0_144/bin/javac 300  
sudo update-alternatives --install /usr/bin/jar jar /opt/jdk1.8.0_144/bin/jar 300   
sudo update-alternatives --install /usr/bin/javah javah /opt/jdk1.8.0_144/bin/javah 300   
sudo update-alternatives --install /usr/bin/javap javap /opt/jdk1.8.0_144/bin/javap 300   

**初次安装会提示选择版本 **

sudo update-alternatives --config java

测试jdk

java -version

参考

1. Ubuntu 安装 JDK 7 / JDK8 的两种方式