How to Install JAVA on Ubuntu 20 04

Linux

How to Install Java on Ubuntu 20.04

Java is a high level, robust, object-oriented and secure rogramming language.Java was developed by Sun Microsystems (which is now the subsidiary of Oracle) in the year 1995.Java runs on all major operating systems and devices.

In this Article we will discuss how to install java on ubuntu 20.04 system.

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Step 1: Install Java

First we will update the repo with apt and install openJdk 14

sudo apt update
sudo apt install openjdk-14-jdk

once it is installed, check java version with following command.

java -version

output:

openjdk version "14.0.2" 2020-07-14
OpenJDK Runtime Environment (build 14.0.2+12-Ubuntu-120.04)
OpenJDK 64-Bit Server VM (build 14.0.2+12-Ubuntu-120.04, mixed mode, sharing)

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Step 2: install multiple versions of Java

you can install multiple versions of java. Here we will install openjdk 11  with the following command.

sudo apt install openjdk-11-jdk

install open jdk 8 

sudo apt install openjdk-8-jdk

Step 3: Setup default Java version

you can setup default java version using the update-alternatives command.

sudo update-alternatives --config java

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output:

There are 3 choices for the alternative java (providing /usr/bin/java).
 Selection    Path                                            Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-14-openjdk-amd64/bin/java      1411      auto mode
  1            /usr/lib/jvm/java-11-openjdk-amd64/bin/java      1111      manual mode
  2            /usr/lib/jvm/java-14-openjdk-amd64/bin/java      1411      manual mode
  3            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      manual mode
Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/lib/jvm/java-11-openjdk-amd64/bin/java to provide /usr/bin/java (java) in manual mode

Now check java version 

java --version

output:

openjdk 11.0.11 2021-04-20
OpenJDK Runtime Environment (build 11.0.11+9-Ubuntu-0ubuntu2.20.04)
OpenJDK 64-Bit Server VM (build 11.0.11+9-Ubuntu-0ubuntu2.20.04, mixed mode, sharing)

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Step 4: Setup Java environment variable

To set Java environment variable, we can check where java is installed by running the below command.

readlink -f /usr/bin/java

ouput:

/usr/lib/jvm/java-11-openjdk-amd64/bin/java

now open /etc/environment file usig nano or vi editor

sudo nano /etc/environment

add below line at the end of the file to above file.

JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64"

save the file and exit.

Now reload the file to effect changes on your current shell.

source /etc/environment

verify Java environment variable with following command.

echo $JAVA_HOME

output:

/usr/lib/jvm/java-11-openjdk-amd64

That's it. Now we have successfully installed Java on Ubuntu 20.04 system.

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