1.sudo su，切换到管理员权限下
2.添加ppa
add-apt-repository ppa:webupd8team/java

3.apt-get update更新资源索引

apt-get update 和 upgrade 的区别

update

update 是同步 /etc/apt/sources.list 和 /etc/apt/sources.list.d 中列出的源的索引，这样才能获取到最新的软件包。

upgrade

upgrade 是升级已安装的所有软件包，升级之后的版本就是本地索引里的，因此，在执行 upgrade 之前一定要执行 update, 这样才能是最新的。

An update should always be performed before an upgrade or dist-upgrade.

upgrade is used to install the newest versions of all packages currently installed on the system from the sources enumerated in /etc/apt/sources.list. Packages currently installed with new versions available are retrieved and upgraded.


4.sudo apt-get install oracle-java8-installer

安装java

5 java -version 查看是否安装成功