Your newBalance variable is a BigDecimal and not a double. I notice the comment in the first method that says "change double newBalance to BigDecimal when working with finances".
You should use BigDecimal when precision is important, such as finances, but at that point it's to late as the value being passed in is a double. If there is any precision loss because of the nature of floating point variables it has already happened.
You should probably do something more like this.
P.S. If you should not put the amount into a double anywhere in the program. You should always deal with it as a String or BigDecimal. BigDecimal has a constructor that takes a String so you can store the value as a BigDecimal as soon as you get the value into your program. [ March 05, 2005: Message edited by: Steven Bell ]