Java

Install

sudo add-apt-repository ppa:webupd8team/java
sudo apt update
# java 7
sudo apt install oracle-java7-installer
# java 8
sudo apt install oracle-java8-installer

Check the version of Java:

java -version
javac -version

If for some reason, the Java version in use is not 1.7.x, you can try to run the following command:

sudo update-java-alternatives -s java-7-oracle

To automatically set up the Java 7 environment variables, you can install the following package:

sudo apt install oracle-java7-set-default
# or
sudo apt install oracle-java8-set-default

If you don’t want to use Oracle Java (JDK) 7 anymore and want to go back to OpenJDK, all you have to do is remove the Oracle JDK7 Installer and the previous Java (OpenJDK, etc.) version will be used:

sudo apt remove oracle-java7-installer

Configuration

To view the current configuration:

update-java-alternatives -l

…alternatively, to be asked:

sudo update-alternatives --config java

JAVA_HOME

How to set JAVA_HOME environment variable in Ubuntu:

To set JAVA_HOME. Edit ~/.bashrc and add the following line:

export JAVA_HOME=/usr/lib/jvm/java-6-sun

It took me a long time to get this working. I think the standard Java is called through a symbolic link and JAVA_HOME will not work when pointed to a symbolic link.