Installing Java

Debian

OpenJDK

Update package information:

apt-get update

Install

apt-get install default-jdk

Or

apt-get install default-jre

Ubuntu

OpenJDK

Then update the package information:

apt-get update

Install

apt-get install default-jre

Or

apt-get install default-jdk

CentOS

OpenJDK

Run the command

yum install java-1.7.0-openjdk

Manage Java

One server can have multiple Java installations at the same time. You can use the update-alternatives command to select the version of Java that will be used by the system by default

sudo update-alternatives --config java

JAVA_HOME variable

Many programs use the JAVA_HOME environment variable to determine where Java is installed. To set this variable, you must first find out exactly where the Java installation is stored

To do this, this command is used:

sudo update-alternatives --config java

Copy the path of the desired version of the program and open /etc/environment in a text editor:

sudo nano /etc/environment

Add the following line to the end of the file (replace the conditional path of the program with the just copied path):

JAVA_HOME="/usr/lib/jvm/java-8-oracle"

Save and close the file. To update the settings, enter:

source /etc/environment

Make sure that the environment variable is set. To do this, type:

echo $JAVA_HOME

The command should return the path you set.