sudo apt-get install openjdk-7-jre 
sudo apt-get install openjdk-7-jdk

sudo apt-get install python-software-properties
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
# 选择需要的版本
sudo apt-get install oracle-java6-installer
# or
sudo apt-get install oracle-java7-installer
# or
sudo apt-get install oracle-java8-installer

update-alternatives --config java
update-alternatives --config javac
java -version