To install Java on Ubuntu 20.04, you can follow these steps. There are different implementations of Java available for Ubuntu, such as OpenJDK and Oracle JDK. In this example, I'll show you how to install OpenJDK, which is the default and widely used implementation of Java on Ubuntu.

Update the Package Lists:

Open a terminal and run the following command to ensure that the package lists are updated:

sudo apt update

Install OpenJDK:

Run the following command to install OpenJDK 11, which is a Long Term Support (LTS) version:

sudo apt install default-jdk

If you specifically need a different version of OpenJDK, you can replace default-jdk with the version you want. For example, openjdk-8-jdk for OpenJDK 8.

Verify the Installation:

After the installation is complete, you can verify that Java is installed by checking the version:

java -version

This command should display information about the installed Java version.

Set the JAVA_HOME Environment Variable (Optional):

While optional, setting the JAVA_HOME environment variable can be useful for certain applications that rely on it. To set it temporarily in the current session, you can use the following command:

export JAVA_HOME=$(readlink -f /usr/bin/java | sed "s:bin/java::")

To set it permanently, you can add the above line to your shell profile file (like ~/.bashrc or ~/.zshrc).