This tutorial explains all the steps required to install OpenJDK 12 on Windows 10. The steps to install OpenJDK 12 on other versions of Windows should be similar to the steps explained in this tutorial.
Open the JDK 12 GA Release site and download the distribution for Windows as highlighted in Fig 1.
Click on the zip download link to download OpenJDK for Windows. Also, verify your download using the given sha256 checksum.
Extract the downloaded zip to the desired location. In my case, I have extracted the downloaded zip to C:\java\java-12. The zip extractor will extract the files to C:\java\java-12\jdk-12.0.1.
This is only step required to install OpenJDK on windows.
Set Environment Variables
In this step, we will configure the environment variables in order to use the OpenJDK from Command Prompt. Open Command Prompt and check the installed version of Java using the command java -version as shown in Fig 2.
It shows the version of Java 8 since my current version of Java is 8. In your case it might show another version of the Java if it's already installed, else it will show the message - Java is not recognized as internal or external command, operable program or batch file.
Right Click -> My Computer(This PC) -> Properties -> Advanced System Settings
The above steps will open the Windows settings panel as shown in Fig 3.
Now click on Environment Variables, select Path under System Variables section and click on Edit. We need to add the path of installed JDK to system Path.
Click on New Button and add the path to installed JDK bin which is C:\java\java-12\jdk-12.0.1\bin in our case. It should look like the one shown in Fig 4.
Press OK Button 3 times to close all the windows. This sets the JDK 12 on system environment variables to access the same from the console.
Notes: Remove existing PATH values specific to previously installed Java. Also update JAVA_HOME, in case it was already set.
Now again open the console and test the Java version as shown in Fig 5.
It must show the OpenJDK version as shown in Fig 5.
These are the easy to install steps required to install OpenJDK on Windows.