Install required software
You'll need to install three different software packages. First, you'll need the Java Development Kit from Oracle. You can find that at this website, and you can use the URL that I'm showing here, or the shortcut "Java.Oracle.com."
From here, go to Java SE, then to the Download link under JDK. You'll need to accept the license agreement and then download the installer for your operating system. As of Java 9, there's only one download for Windows, and that's for 64-bit Windows.
Now you have to download and install IntelliJ IDEA. And you can get it from the Jet Brains website here. Use just the first part of the URL: www.jetbrains.com/idea/download and you'll go automatically to the appropriate page for your operating system. Download and install the Community edition of IntelliJ IDEA.