E: Unable to locate package openjdk-8-jre-headless

在ubuntu上安装JDK时遇到问题：

$ apt-get install openjdk-8-jre-headless

Reading package lists... Done

Building dependency tree

Reading state information... Done

E: Unable to locate package openjdk-8-jre-headless

解决：

add-apt-repository ppa:openjdk-r/ppa

apt-get update

apt-get install openjdk-8-jre-headless