If you using firebase and want to debug for Oauth or Messaging you will need to add a certificate SHA1 from your app key. You might need it for other features but this is what I'm sure about. Assuming java is installed then wherever you java is installed is where you will need to point to for
Example of File locationC:\Program Files (x86)\Java\jre1.8.0_60\bin
"keytool -exportcert -list -v -alias "YOURALIAS" -keystore YOURKEYFILE.jks > file.txt"
I would output to a file so you can copy it later...
Authenticating Your Client