Create a class called Invoice in your assignment source package. An Invoice should include four pieces of information as attributes(instance variables) - a part number of type String, a part description of type String, a purchasing quantity of type Int, and a price per item of type double. Your class should have a full constructor that initializes all the four attributes. Provide a set and a get method for each attribute. In addition, provide a method named getInvoiceTotal that calculates the invoice total, purchasing quantity * price per ite, and returns the invoice total. If the quantity is negative, returns 0.

Create an test app named InvoiceTest in the same package that demonstrates class Invoice's capabilities.