A good answer might be:

• How many objects are in the system the very instant the program starts running?
  • Zero.
  • (This is always the answer to this question.)
• How many objects are in the system just before the program stops running?
  • One, the object referenced by car.
  • (The String object in the println has already become garbage.)

When a program starts running there are no objects, just class definitions and a static main() method. Usually main() then constructs some objects and calls their methods to do the work of the program. In our example, main() constructed just one object and then called its calculateMPG() method.

The picture shows the variable car in the static main() method referring to the object that has been constructed following the plan given in the class definition of Car.

The static main() method is actually part of the MilesPerGallon class, which is not shown in the picture.

QUESTION 12:

Could several objects of type Car be constructed?