How do i implement OOPs here and wat pattern do i follow

[Anil Verghese]

Hi,

I have a program , I shall explain it to you can you suggest the best design pattern and how to implement OOPs in it.

Problem: Tax

In a shop there are two types of commodities ordinary and imported. In the ordinary group the following are exempted from taxes , bookas, medicinal and food. Apart from that all the things have tax of 10%. the tax has to be rounded to .05.
In the imported category every thing has tax of an extra 5% with no exemptions at all.

The input will be as
Input 1:
1 book at 12.49
1 music CD at 14.99
1 chocolate bar at 0.85

Input 2:
1 imported box of chocolates at 10.00
1 imported bottle of perfume at 47.50

Input 3:
1 imported bottle of perfume at 27.99
1 bottle of perfume at 18.99
1 packet of headache pills at 9.75
1 box of imported chocolates at 11.25

OUTPUT

Output 1:
1 book : 12.49
1 music CD: 16.49
1 chocolate bar: 0.85
Sales Taxes: 1.50
Total: 29.83

Output 2:
1 imported box of chocolates: 10.50
1 imported bottle of perfume: 54.65
Sales Taxes: 7.65
Total: 65.15

Output 3:
1 imported bottle of perfume: 32.19
1 bottle of perfume: 20.89
1 packet of headache pills: 9.75
1 imported box of chocolates: 11.85
Sales Taxes: 6.70
Total: 74.68

How do i go about with this

[Campbell Ritchie]

Several ways to do it.

Set up an enum with different rates of tax in, use that to feed rates to different classes.

Set up a Commodity class (abstract) with Book, Aspirin, Chocolate subclasses and tax fields. You can set up (maybe static) methods which calculate the tax from the price.

Create an Imported annotation, then you can use that as a tag and enhance the tax.