Question

Suppose I have the following classes:

class car1 {}
class car2 {}
class car3 {}
class car4 {}

Support I also have the method: queryCar()

private Object queryCar()
{
     int version = getCarVersion(); // returns car version
     if (version == 1)
         return new car1();
     else if (version == 2)
         return new car2();
     else if (version == 3)
         return new car3();
     ...
}

I have another method, doStuff()

private void doStuff()
{
     // psudocode
     if queryCar() returns a car1, I want to create a JPanel with an instance member of type car1
}

How do I accomplish said psudocode? InstanceOf works for determining the class. However, I only want one class to autogenerate that car on runttime. (Thinking of an analog of C++ pointers in java)

Answer 1

You can do this using instanceof with Object like you did, but it might make it easier to use a car interface like this:

interface Car {}
class Car1 implements Car {}

private void doStuff {
    Car car = queryCar();
    if(car instanceof Car1) {
        Car1 theCar = ((Car1) car);
        theCar.car1OnlyMethod();
        //Or
        ((Car1) car).car1OnlyMethod();
    }
}