Create a class called Invoice that a hardware store might use to represent an invoice for an item sold at the 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 pur-chased (type int) and a price per item (double). Your class should have a constructor that initializes the four instance variables. Provide a set and a 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.