If you don't have JDK installed on your machine, you can install it by clicking on Install JDK.

To verify it's installed, create a new terminal and try running the following command:

java -version

You should see something similar to the following:

java version "1.8.0_311"
Java(TM) SE Runtime Environment (build 1.8.0_311-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.311-b11, mixed mode)

The detailed output will be based on the JDK you install.