enthuware.ocajp.i.v7.2.1117

[jojo314519]

I ran it. It only prints:

Automobile: drive


Why does test say answer is:
It will print:
Automobile: drive
Truck: drive
Truck: drive
in that order.


Thanks.

[admin]

Please make sure you are running the code exactly as given.

[lostintesting]

no, he's right. the code is:

class Automobile{
public void drive() { System.out.println("Automobile: drive"); }
}

public class Truck extends Automobile{
public void drive() { System.out.println("Truck: drive"); }
public static void main (String args [ ]){
Automobile a = new Automobile();
Truck t = new Truck();
a.drive(); //1

there is only one line that calls the drive statement. a.drive(); there is not way to get three lines of output.

[admin]

Please observe lines marked //1 , //2, and //4.

[baichen7788]

I don't understand why t=(Truck)a will result in ClassCastException.

[admin]

Does the variable a refer to an object of type Truck at run time?

[baichen7788]

class Automobile{
public void drive(){}
}



public class Truck extends Automobile {
public void drive(){}

public static void main(String[] args) {
Automobile a = new Automobile();
Truck t = new Truck();
t=(Truck) a;
}

}

[admin]

So, what type of object does the variable a refer to??
a refers to an object of type Automobile. An Automobile is not a Truck. That is why CCE is thrown.
Please go through Java book to understand how casting works. Or you may also go through this tutorial: https://www.baeldung.com/java-type-casting