[Ubuntu] 14.04版本安装JDK8失败

系统：Ubuntu 14.04

编译 Android 7.1 系统需要 JDK 8，但是安装时失败，

$ sudo apt install openjdk-8-jdk
Reading package lists... Done
Building dependency tree 
Reading state information... Done
E: Unable to locate package openjdk-8-jdk

解决办法：

$ sudo add-apt-repository ppa:openjdk-r/ppa
$ sudo apt-get update
$ sudo apt-get install openjdk-8-jdk