ITEC 120 2009spring ibarland nokie jmdymacek

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lab07a
eBay fees
using if-else-if

Work on today's lab with a partner. You can write the following two-to-three methods in a class named, say, ebayExpert.

Calculating eBay fees

If you sell an item on eBay, you are charged several different fees. Today, we will compute one of those: the “final-value fee”, which depends on how much the item sold for (its “sale price”).

(Note that there is also a flat fee just for using eBay to start with, as well as an optional extra fee if you want some fancy pictures in your listing. We'll handle those other fees in a future lab.) The final value fee is 8.75% of the (up to) first $25 of the sale price, and 3.50% of the rest of the sale price.

1. Make a new BlueJ Project for lab07a, make a new class EbayExpert, and paste in the following:

   class EbayExpert { /** computeFVFee computes the final-value fee which eBay charges to a seller. * @param ________ _______________ * @return _____________________, in dollars. */ ______ computeFVFee( ______ _______ ) { return 56.78; // A dummy, stub result. } }

2. As always, first write a test-program which tests several inputs. Can you find test-cases that make your arithmetic easy, yet enough test-cases to convince you that any code passing your tests is always correct? (We will do some in class, and you'll need to do some on your own). Fill out the javadoc and function signatures for computeFVFee.
3. Write the function body for computeFVFee, and run your test-driver.
   

4. The above problem was simplified a bit; eBay's final-value-fee doesn't have just the two tiers (0.00, 25.00] and (25.00,+∞), but actually three: (0.00,25.00], (25.00,1000.00], and (1000.00,+∞). Those round and square parentheses are math-ese for intervals with open and closed endpoints; eBay presents this same information in a table.
   Go back and change your program to use eBay's actual final-value-fee.

   Use the if-else-if statement, for this three-tier problem. Match up those curly-brackets carefully!

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If you finish…

Modify your program to account for two additional fees:

• The insertion fee, where we will assume the auction's starting price is $0.01. (The assumption makes this a flat fee.)
• The picture-hosting fee of “first picture free, each additional picture $0.15”. Note that your method needs to be given two pieces of information: the auction's sale-price, and the number of pictures used.
• a fee of $0.35, if the seller used “gallery plus”. Note that your method needs to be given a third piece of information: whether or not the seller used “gallery plus”. Use a boolean value to represent this. (Boolean values are discussed in the textbook §5.4.)
How can you combine the method for computing the final-value-fee with all these other fees? See if you can do it without needing to change your first method. You can use “this.methodName(args…)” to have your method call another method you wrote previously!

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©2009, Ian Barland, Radford University Last modified 2009.Mar.03 (Tue)

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