get and set method

Create a class called Invoice that a hardware store might use to represent an invoice for an item sold at a store. An Invoice should include four pieces of information as instance variables ? a part number (type String), a part description (type String), a quantity of the item being purchased (type int), a price per item (type double). Your class should have a constructor that initialises the four instance variables. Provide a set and get method for each instance variable. In addition provide a method named getInvoiceAmount that calculates the invoice amount (i.e multiplies the quantity by the price per item), then returns the amount as a double value. If the quantity is not positive, it should be set to 0. If the price per item is not positive it should be set to 0.0. Write a test application named InvoiceTest that demonstrates class Invoice?s capabilities