Ubuntu 安装 JDK8

$sudo apt-get install python-software-properties
$sudo apt-get install software-properties-common

$ sudo add-apt-repository ppa:webupd8team/java　

$ sudo apt-get update

$ sudo apt-get install oracle-java8-installer
$ java -version
java version "1.8.0_05"
Java(TM) SE Runtime Environment (build 1.8.0_05-b13)
Java HotSpot(TM) Server VM (build 25.5-b02, mixed mode)

sudo update-java-alternatives -s java-8-oracle