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So, you better try to use FileOutputStream and ObjectOutputStream (concept of serialization) in your function.

So, you can get text from your file into a string and try using nextInt(). Ain't you?

1. Where are you getting menu choice?
2. Are you sure that in file there is no space between your operator and the immediate operand?
3. You better try using nextInt() or whatever type of values...

Can you kindly post through your whole code so that we could look over that and inside the findTotal() method, you used str.charAt(0), should it always check the character position at 0?
Anyways,...