How can I check if Java is installed on my Mac? I have gone into Terminal and typed 

java -v


for which it responds with 

No Java runtime present, requesting install.


But I am not sure if that is confirming if Java is not installed or whether the Java SDK is not installed.
If it's responding with No Java runtime present, requesting install.... well, it's not installed. I believe that Apple's default installer still installs Java 6; I'd recommend getting the latest version (right now Java 8u144) from here.

With Java 8, java -v fails with Unrecognized option: -v. Use java -version instead.