Java IS case-sensitive. The f or F you are saying is different, it doesn't apply to variable names or method names etc. There is even l or L for showing as long, it doesn't mean Java is not case sensitive.
Please revise your display name to meet the JavaRanch Naming Policy. To maintain the friendly atmosphere here at the ranch, we like folks to use real (or at least real-looking) names, with a first and a last name.