Exercise 5 on page 415. Replace its last sentence with: Add the controls displaying the initial gas mileage upon creating each objects, and updating them after incrementing or decrementing it using operators ++ and -- .
Car and CarDemo classes should be defined in separate files. The buttons for MPG incrementing and decrementing should be colored differently.
Create an application named CarDemo that declares at least two Car objects and demonstrates how they can be incremented using an overloaded ++ operator. Create a Car class that contains a model and a value for miles per gallon. Include two overloaded constructors. One accepts parameters for the model and miles per gallon; the other accepts a model and sets the miles per gallon to 20. Overload a ++ operator that increases the miles per gallon value by 1. The CarDemo application creates at least one Car using each constructor and displays the Car values both before and after incrementation.