Installing the Java Development Kit (JDK) on Ubuntu

The Java Development Kit (JDK) is essential for developing and running Java-based applications. This tutorial provides a comprehensive guide to installing the JDK on Ubuntu Linux. We’ll focus on the recommended approach using the OpenJDK, which is freely available and easily managed through Ubuntu’s package manager.

Prerequisites

An Ubuntu Linux system (desktop or server).
A user account with sudo privileges (necessary to install software).
An active internet connection.

Step 1: Updating the Package List

Before installing any new software, it’s crucial to update your system’s package list. This ensures you have the latest information about available packages and dependencies. Open a terminal window and run the following command:

sudo apt update

This command retrieves package information from the configured repositories.

Step 2: Installing the JDK

Ubuntu provides OpenJDK as a readily available package. To install the latest version, use the following command:

sudo apt install default-jdk

This command installs the default JDK, which typically includes the Java Runtime Environment (JRE) and development tools like the Java compiler (javac). If you need a specific version of OpenJDK (e.g., OpenJDK 8, 11, 17, or 21), you can specify it explicitly:

sudo apt install openjdk-8-jdk
sudo apt install openjdk-11-jdk
sudo apt install openjdk-17-jdk
sudo apt install openjdk-21-jdk

Choose the version that best suits your project requirements.

Step 3: Verifying the Installation

After the installation is complete, verify that Java is installed correctly by checking its version. Run the following command in the terminal:

java -version

This command should display the Java version information, confirming that the JDK has been installed successfully. You should see output similar to this:

openjdk version "17.0.7" 2023-04-18
OpenJDK Runtime Environment (build 17.0.7+7-Ubuntu-122.04)
OpenJDK 64-Bit Server VM (build 17.0.7+7-Ubuntu-122.04, mixed mode)

You can also verify the Java compiler:

javac -version

Step 4: Setting the `JAVA_HOME` Environment Variable (Optional but Recommended)

While not strictly required, setting the JAVA_HOME environment variable is a good practice, especially if you’re working on multiple Java projects or using tools that rely on it. JAVA_HOME points to the root directory of your JDK installation.

Determine the installation path: The location of the JDK varies depending on the version and Ubuntu release. A common location is /usr/lib/jvm/java-<version>-openjdk-<architecture>. You can list the directories under /usr/lib/jvm/ to find the correct one.
Set the JAVA_HOME variable: You can set this variable in your shell’s configuration file (e.g., .bashrc, .zshrc) or system-wide in /etc/environment. For example, to set it in .bashrc:
```
echo 'export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64' >> ~/.bashrc
source ~/.bashrc
```
Replace /usr/lib/jvm/java-17-openjdk-amd64 with your actual JDK installation path. The source ~/.bashrc command reloads your shell configuration to apply the changes.
Update the PATH variable: Add the JDK’s bin directory to your PATH so you can run Java commands from anywhere. Add this line to your shell configuration file:
```
echo 'export PATH=$PATH:$JAVA_HOME/bin' >> ~/.bashrc
source ~/.bashrc
```

Conclusion

You have successfully installed the Java Development Kit (JDK) on your Ubuntu system. You can now start developing and running Java applications. Remember to choose the appropriate JDK version for your project and configure the JAVA_HOME environment variable for easier management.