请按照以下步骤安装oracle java：

Please follow below steps to install oracle java:

下载 最新 Java SE SDK版本。

Download the latest Java SE SDK version.

http：// www.oracle.com/technetwork/java/javase/downloads/index.html

解压档案：

tar -xzvf jdk-8-linux-x64.tar.gz
mv jdk1.8.0 /opt 
cd /opt/jdk1.8.0

此步骤将下载的Java版本作为替代方案，并将其切换为默认值：

This step registers the downloaded version of Java as an alternative, and switches it to be used as the default:

update-alternatives --install /usr/bin/java java /opt/jdk1.8.0/bin/java 1
update-alternatives --install /usr/bin/javac javac /opt/jdk1.8.0/bin/javac 1
update-alternatives --install /usr/lib/mozilla/plugins/libjavaplugin.so mozilla-javaplugin.so /opt/jdk1.8.0/jre/lib/amd64/libnpjp2.so 1
update-alternatives --set java /opt/jdk1.8.0/bin/java
update-alternatives --set javac /opt/jdk1.8.0/bin/javac
update-alternatives --set mozilla-javaplugin.so /opt/jdk1.8.0/jre/lib/amd64/libnpjp2.so

测试

检查您正在运行的Java版本

To check the version of Java you are now running

java -version

输出

java version "1.8.0"
Java(TM) SE Runtime Environment (build 1.8.0-b132)
Java HotSpot(TM) 64-Bit Server VM (build 25.0-b70, mixed mode)

要检查浏览器插件，请浏览 http://www.java.com/ 并点击我有Java吗？

To check the browser plugin browse to http://www.java.com/ and click "Do I have Java?"

参考： https://askubuntu.com/questions/437776 / ubuntu-13-04-could-to-install-jdk7