I don't know how to code this in Java

Create a GUI application that calculates and displays the total travel expenses of a business person on a trip. Here is the information that the user must provide: Number of days on the trip Amount of airfare, if any Amount of car rental fees, if any Number of miles driven, if a private vehicle was used Amount of parking fees, if any Amount of taxi charges, if any Conference or seminar registration fees, if any Lodging charges, per night The company reimburses travel expenses according to the following policy: $37 per day for meals Parking fees, up to $10.00 per day Taxi charges up to $20.00 per day Lodging charges up to $95.00 per day If a private vehicle is used, $0.27 per mile driven The application should calculate and display the following: Total expenses incurred by the businessperson The total allowable expenses for the trip The excess that must be paid by the businessperson, if any The amount saved by the businessperson if the expenses were under the total allowed