Using Java requires you to install a JDK ("Java Development Kit") or JRE ("Java Runtime Environment"). We'll use a JDK since it can do everything a JRE can, plus more.
As of 2019, there are two major JDKs: OpenJDK (also known as AdoptOpenJDK) and the Oracle JDK. OpenJDK and Oracle JDK provide the same functionality, and are even built from the same code base. They differ only in their packaging and licensing.
OpenJDK is free for use in all situations. Oracle JDK requires a paid-for commercial license when used in a production setting.
Most personal users will probably want to use OpenJDK, since it's easier to acquire and install and that's what we'll be covering here.
First you should check if Java is already installed
java -versionIf you see a non-empty output like below then Java is already installed on your machine and you are good to go
openjdk version "13.0.2" 2020-01-14
OpenJDK Runtime Environment AdoptOpenJDK (build 13.0.2+8)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 13.0.2+8, mixed mode, sharing)If you don't see the output like above then you need to install Java on your system
brew install openjdkIf you're curious, you can list all the available JDK versions via:
brew search jdkThere will be a lot of options here! If you are not a serious Java developer, don't worry about them, and just use the default openjdk.
Once you've done that, check if Java is correctly installed by running the java -version command again.
Open a web browser and go to https://adoptopenjdk.net/. Select "OpenJDK 11 (LTS)" and "HotSpot". Click the big "Latest release" button and run the installer file that gets downloaded.
Once you've done that, check if Java is correctly installed by opening a new Terminal session and running the java -version command again.