Install OpenJDK on Ubuntu

Why OpenJDK

• To develop Java applications you need the JDK (the full Java Development Kit).
• Many enterprise and server applications run on Java.
• OpenJDK is the free and open-source alternative to Oracle's Java.

The packages:

• JRE (openjdk-17-jre) lets you run Java programs.
• JDK (openjdk-17-jdk) lets you also compile and develop.
• default-jdk installs the recommended JDK of your Ubuntu version.

Check if Java is installed

java -version

Install OpenJDK

Update the package list:

sudo apt update

Install the default JDK:

sudo apt install default-jdk

Or choose a version:

sudo apt install openjdk-17-jdk

Find the packages that you can install:

sudo apt-cache search openjdk

Check the install

java --version
javac --version

Set JAVA_HOME

Find the path:

readlink -f $(which javac) | sed "s:/bin/javac::"

Open your shell file:

nano ~/.bashrc

Add (use the path you found):

export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64
export PATH=$PATH:$JAVA_HOME/bin

Load the change:

source ~/.bashrc

For all users, put the lines in /etc/environment or in a file in /etc/profile.d/.

Switch between versions

If several versions are installed:

sudo update-alternatives --config java

Remove OpenJDK

sudo apt remove openjdk-17-jdk openjdk-17-jre

Quick recap

• sudo apt install default-jdk is the easy way.
• Check with java --version.
• Set JAVA_HOME in ~/.bashrc.