Android Question What compiler Error for undefined variables

Sometimes the compiler tells me that I have a variable that is not used so I comment it out and compile and run my program and everything seems fine.

Later on I scroll into my program and find a place where I am setting this variable (that I have now comment out or deleted). But am really not using.

Is there any setting that I can tell the compiler I want an Error for any Undefined Variables?

I am sure someday having an undefined variable and using it somewhere else is going to cause me problems.

Thanks

BobVal