Step 1: Update Your System

As it is a good practice to update your system before going to install any new package so update the system.

sudo apt update

Step 2: Install Java OpenJDK JDK on Ubuntu 20.04

To install the Java OpenJDK on your Ubuntu 20.04 system type the below command in your terminal.

For Java 11 run the following command. And press Y when prompted.

sudo apt install openjdk-11-jdk

Output:

You’ll see the similar output upon successful installation.

Processing triggers for gnome-menus (3.36.0-1ubuntu1) …
 Processing triggers for man-db (2.9.1-1) …
 Processing triggers for ca-certificates (20190110ubuntu1) …
 Updating certificates in /etc/ssl/certs…
 0 added, 0 removed; done.
 Running hooks in /etc/ca-certificates/update.d…
 done.
 done.
 Processing triggers for sgml-base (1.29.1) …
 Setting up x11proto-dev (2019.2-1ubuntu1) …
 Setting up libxau-dev:amd64 (1:1.0.9-0ubuntu1) …
 Setting up libice-dev:amd64 (2:1.0.10-0ubuntu1) …
 Setting up libsm-dev:amd64 (2:1.2.3-1) …
 Setting up libxdmcp-dev:amd64 (1:1.1.3-0ubuntu1) …
 Setting up x11proto-core-dev (2019.2-1ubuntu1) …
 Setting up libxcb1-dev:amd64 (1.14-2) …
 Setting up libx11-dev:amd64 (2:1.6.9-2ubuntu1) …
 Setting up libxt-dev:amd64 (1:1.1.5-1) …

For Java 8 run the given command.

sudo apt install -y openjdk-8-jdk

Output:

Upon successful installation you’ll see the similar output.

provide /usr/bin/idlj (idlj) in auto mode
 update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/wsimpo
 rt to provide /usr/bin/wsimport (wsimport) in auto mode
 update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/jsadeb
 ugd to provide /usr/bin/jsadebugd (jsadebugd) in auto mode
 update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/native
 2ascii to provide /usr/bin/native2ascii (native2ascii) in auto mode
 update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/javah 
 to provide /usr/bin/javah (javah) in auto mode
 update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/clhsdb
  to provide /usr/bin/clhsdb (clhsdb) in auto mode
 update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/extche
 ck to provide /usr/bin/extcheck (extcheck) in auto mode
 update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/hsdb t
 o provide /usr/bin/hsdb (hsdb) in auto mode
 update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/schema
 gen to provide /usr/bin/schemagen (schemagen) in auto mode
 update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/xjc to
  provide /usr/bin/xjc (xjc) in auto mode
 update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/jhat t
 o provide /usr/bin/jhat (jhat) in auto mode
 update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/wsgen 
 to provide /usr/bin/wsgen (wsgen) in auto mode
 Setting up openjdk-8-jdk:amd64 (8u252-b09-1ubuntu1) …
 update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/applet
 viewer to provide /usr/bin/appletviewer (appletviewer) in auto mode
 Processing triggers for mime-support (3.64ubuntu1) …
 Processing triggers for hicolor-icon-theme (0.17-2) …
 Processing triggers for gnome-menus (3.36.0-1ubuntu1) …
 Processing triggers for libc-bin (2.31-0ubuntu9) …
 Processing triggers for desktop-file-utils (0.24-1ubuntu2) …

Step 3: Install Java OpenJDK JDK Headless

To install JDK headless simply fire the below command in your terminal.

For Java Headless 11 JDK.

sudo apt install -y openjdk-11-jdk-headless

For Java Headless 8 JDK.

sudo apt install -y openjdk-8-jdk-headless

Step 4: Install Java OpenJDK JRE on Ubuntu 20.04

Hit the command given below in your terminal.

For Java JRE 11.

sudo apt install -y openjdk-11-jre

Java JRE 8.

sudo apt install -y openjdk-8-jre

For Java JRE headless

You can install Java JRE headless with the help of following command.

For Java 11.

sudo apt install -y openjdk-11-jre-headless

For Java 8.

sudo apt install -y openjdk-8-jre-headless

Step 5: How To Set Default Java Version on Ubuntu 20.04

Run the below command to set the default java version on Ubuntu 20.04.

sudo update-alternatives --config java

Select the number from the list you want to make default java version.

Verify the installed Java version by running the below command.

java -version

Output:

sabi@Ubuntu:~$ java -version
 openjdk version "1.8.0_252"
 OpenJDK Runtime Environment (build 1.8.0_252-8u252-b09-1ubuntu1-b09)
 OpenJDK 64-Bit Server VM (build 25.252-b09, mixed mode)

Step 6: Setting Up Environment Variables

For setting up environment variables you’ve to create a new file. To do this run the following command.

sudo nano /etc/profile.d/java.sh

And then provides the variables paths where the Java is installed.

export PATH=$PATH:/usr/lib/jvm/java-11-openjdk-amd64/bin/
export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64/
export J2SDKDIR=/usr/lib/jvm/java-11-openjdk-amd64/

And finally source the file.

source /etc/profile.d/java.sh

That’s it you’ve successfully installed Java.

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