Java - How to check if a abstract superclass is a particular subclass

Question

The question might look trivial but I couldn't find the solution anywhere!

I have an abstract superclass Vehicle, and there are 4 subclasses that extend it, viz Car, Bus, Lorry and Bicycle.

I also have an ArrayList<Vehicle> V containing many Vehicle objects but we don't know which type of vehicle.

Now I am not able to calculate the number of Cars in the ArrayList V

int carCount = 0;
for (Vehicle ob: V){
    if (ob is a car) {
        carCount++;
        }
    }
return carCount;

Would like to know what should be the code inside if(ob is a car) in the code above.

Thanks!

score 4 · Accepted Answer · answered Sep 18 '17 at 12:27

4

if(ob instanceof Car)

Please try this

answered Sep 18 '17 at 12:27

BatyaGG

score 3 · Answer 2 · answered Sep 18 '17 at 12:59

3

You can do it in one line, if you use java-8:

V.stream().filter(Car.class::isInstance).count();

answered Sep 18 '17 at 12:59

Anton Balaniuc

score 2 · Answer 3 · answered Sep 18 '17 at 12:39

2

You are looking for

if (ob instanceof Car) {
    carCount++;
}

Get detailed information here: Oracle: instanceof

answered Sep 18 '17 at 12:39

Mathias Bader

3 Answers3