Quite apart from the ten programming sins you have in that code, the Java error is like this:
You have a while-loop which iterates through the rows of the spreadsheet. In that loop you have a local variable named rowarrylist, which you use to collect stuff from the spreadsheet.
But it's a local variable so it's unavailable after the loop finishes. Your solution was to create another variable of the same name and assign it a null value. That doesn't work, it will give you a NullPointerException.
Solution: Declare the variable outside the loop so it would be available to other code which needs it.