Cant return an object type?

Question

I have a method that should return an object type at the end. im using if statements and returning object type accordingly, but i keep getting an error saying i didnt return anything? now sure how to solve it.

private Door pickADoor(Door door1, Door door2, Door door3) {
        Random generator = new Random();
        int numOfDoors = generator.nextInt(3) + 1;
        if (numOfDoors == 1) {
            door1.choose();
            System.out.println("The player selected door A");
            return door1;
        } else if (numOfDoors == 2) {
            door2.choose();
            System.out.println("The player selected door B");
            return door2;
        } else if (numOfDoors == 3) {
            door3.choose();
            System.out.println("The player selected door C");
            return door3;
        }
    }

Answer 1

You miss the else block. Although logically there shouldn't be any, the compiler cannot know that. So add something like:

 else {
      throw new IllegalStateException ("cannot happen");
 }

Edit: or simply assert false , as suggested below. This doesn't give explanation but here clearly is not necessary.

Answer 2

It is complaining because you don't cover all of the possibilities in your if statements, you only cover the cases where numOfDoors is 1,2, or 3. Maybe nofOfDoors can only be 1,2 or 3 but the compiler doesn't know that.

One possible fix: on your final else

change

else  if(numOfDoors == 3) {

to be

else {

So it covers all other values.

Answer 3

The issue is that java thinks there could be a scenario in which numOfDoors could be a number other than 1, 2, or 3. Logically, however, we know that your random number will be from 1-3 inclusive, it's just java doesn't realize this.

Instead, you can change your last else if to this:

        else {
          door3.choose();

           System.out.println("The player selected door C"); 
           return door3;
        }

    }

Answer 4

You are missing a return statement in after the if block,

    private Door pickADoor(Door door1, Door door2, Door door3) {

    Random generator = new Random();
    int numOfDoors = generator.nextInt(3) + 1;

    if (numOfDoors == 1) {
        door1.choose();

        System.out.println("The player selected door A");
        return door1;

    }

    else if (numOfDoors == 2) {
        door2.choose();

        System.out.println("The player selected door B");
        return door2;
    }

    else if (numOfDoors == 3) {
        door3.choose();

        System.out.println("The player selected door C");
        return door3;
    }
    // decide what should you do here
    throw new IllegalStateException("only 3 doors selectable");

}

Answer 5

you need return statement for all other scenarios. Example if numOfDoors would be greater than 3 or less than 1. In this case nothing would be returned. It is inadmissible. Just add to your code

else return null;

...or default door... depend of your logic