Not every DevOps or software quality tool requires the Java Runtime Environment in order to function. Source code management tools, like Git and Subversion, fall into the non-Java category, as do popular configuration management tools, like Chef and Puppet. But there are a large number of Java build tools and Java testing tools that do require a Java Development Kit installation, with a few of the most noteworthy being Groovy, Gradle and Jenkins CI. Each of these tools requires a JDK download and subsequent JRE installation in order for any of their features to function.
In this Java video tutorial, we'll walk through how to choose the correct JDK download and perform the JRE installation. This video also shows you how to configure a Java 10 installation by setting up the important JAVA_HOME system variable and adding the JDK's bin directory to the Windows PATH variable. And while this tutorial demonstrates a Windows-based JDK download and JRE installation, the steps are essentially the same, regardless of whether you are a doing a JDK download on macOS or performing the JRE installation on a Linux machine.
The JDK download and JRE installation are fairly straightforward processes. However, there are a couple of points that are worth clarifying before watching the installation tutorial.
Download the Java 10 JDK
First, the JDK download includes the JRE, so the JRE is not a separate download. The JRE is packaged along with the JDK. Along with the JRE, the JDK download also includes a variety of other development tools, such as a Java compiler and a Java package and archive tool. It is possible to download just the JRE from Oracle, but this download doesn't include the extra development tools that products like Jenkins or Gradle need. So, when visiting Oracle's software site, make sure the JDK download is selected and not just the plain old JRE.
Include the JDK to the PATH
Secondly, it is important to point the OS' PATH variable to the bin directory of the JDK installation. The bin directory is where the compilation and archiving tools are found. By placing the bin directory of the JDK installation on the OS' global PATH variable, a command-line program can easily invoke the Java tools and utilities by name rather than having to include the name of the directory in which they were installed. In this Java video tutorial, the Windows PATH variable will be configured to include the following directory: C:\_jdk10\bin.
Configure JAVA_HOME on Windows
Thirdly, whenever you perform a JDK download and install, it is important to set up a new environment variable named JAVA_HOME and point it to the directory in which the JDK was installed. Tools like Gradle, Tomcat or Jenkins require that Java look for this JAVA_HOME environment variable when they start, so it is important to configure it correctly. In this Java tutorial, the JDK will be installed into a directory named C:\_jdk10, which is the value that will be given to the JAVA_HOME variable.
Not to worry, the accompanying Java video tutorial will walk you through each of these configurations. Be aware of what these steps are and why they are being performed to get the most out of the video.