Need help writing java for this question

6) Construct a program, named Discount.java, which calculates the bill for a customer at a Department Store The program requires the user to enter the sales amount. If the sales amount is more than 300 dollars, the customer gets a 30% discount. If the sales amount is more than $100, but less than or equal to $300, he/she is entitled to a 10% discount. The customer is NOT entitled to a discount if the sale is less than $100. A tax of 7% is added to the final sales amount. The program calculates and prints the final amount he/she owes to the store. All inputs and outputs happen through dialog boxes. An error dialog appears, if the user enters a sales amount less than or equal to $0. Note that money amounts are formatted with 2 decimals. Sample execution : n Somple execution2 Somple execution 3 trout The tinal bail i$367.01 Sample execution 4 I Enter sales ampunt 67 90