Problem Statement:

On a retail website, the following discounts apply: 
1. If the user is an employee of the store, he gets a 30% discount 
2. If the user is an affiliate of the store, he gets a 10% discount 
3. If the user has been a customer for over 2 years, he gets a 5% discount. 
4. For every $100 on the bill, there would be a $ 5 discount (e.g. for $ 990, you get $ 45 as a discount). 
5. The percentage based discounts do not apply on groceries. 
6. A user can get only one of the percentage based discounts on a bill.  

Write a program with test cases such that given a bill, it finds the net payable amount. 

Please note the stress is on object oriented approach and test coverage.

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Solution:

Classes Hierarchy*:

				Discount 
							DiscountDecorator*
BillingDiscount				EmployeeDiscount 	AffiliateDiscount 	LoyalCustomerDiscount

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					User(Discount)
	RegularCustomer		 LoyalCustomer  		 Employee 			Affiliate
	(BillingDiscount)   (LoyalCustomerDiscount)		(EmployeeDiscount)		(AffiliateDiscount)		 
	
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* Read Javadocs for details around the purpose of each class.

** The class files are not required in VCS.