Java
Installing the Default JRE/JDK
The easiest option for installing Java is using the version packaged with Ubuntu. Specifically, this will install OpenJDK 8, the latest and recommended version.
apt update
sudo apt-get update
install JRE(Java Runtime Environment)
sudo apt-get install default-jre
Install JDK(Java Development Kit)
sudo apt-get install default-jdk
The JDK does contain the JRE.
Installing the Oracle JDK
If you want to install the Orcale JDK, which is the offical version distributed by Oracle.
Update your package repository
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
Oracle JDK 8
sudo apt-get install oracle-java8-installer
Oracle JDK 9
sudo apt-get install oracle-java9-installer
Managing Java
There can be multiple Java installations on one server. You can configure which version is the default for use in the command line by using update-alternatives, which manages which symbolic links are used for different commands.
sudo update-alternatives --config java
You can now choose the number to use as a default.
Setting the JAVA_HOME Environment Variable
.bash_profile or .profile에 아래의 변수를 추가한다.
JAVA_HOME='/usr/bin/java