Why no Unchecked Cast warning when using delegate method?

Question

I have a generic factory that returns a controller and I would like to avoid an Unchecked Cast warning without using @SuppressWarnings.

In my example below, the factory uses two different ways of returning a controller. The first one ((BallController<T>) getBaseballController();) causes an Unchecked Cast warning. The second one ((BallController<T>) someOtherClass.getFootballController();) does not cause any warnings.

public class BallControllerFactory {

    public BaseballController getBaseballController() {
        return new BaseballController();
    }

    public <T extends Ball> BallController<T> getBallController(T ball) {
        if(ball instanceof Baseball) {
            return (BallController<T>) getBaseballController();
        }
        else if(ball instanceof Football) {
            SomeOtherClass someOtherClass = new SomeOtherClass();
            return (BallController<T>) someOtherClass.getFootballController();
        }

        //No controller found
        return null;
    }
}

As you can see, just by moving the getXXXController method to a delegate class, the warning is eliminated. Here is the SomeOtherClass, just so you can see nothing special is happening.

public class SomeOtherClass {
    public FootballController getFootballController() {
        return new FootballController();
    }
}

My question is, why is it that when I use a delegate method to return the controller I do not get the Unchecked Cast warning, but when I use a local method I do?

For the sake of completeness, here are the other class definitions (all are empty classes).

public class BallController<T extends Ball>
public class BaseballController extends BallController<Baseball>
public class FootballController extends BallController<Football>
public class Ball
public class Baseball extends Ball
public class Football extends Ball

Answer 1

Although your warning message are inconsistent for some reason (you should get warnings on both), the fix for your situation is to change:

public <T extends Ball> BallController<T> getBallController(T ball) {

to

public <T extends Ball> BallController<?> getBallController(T ball) {

and remove the casts:

        return (BallController<T>) getBaseballController();
        return (BallController<T>) someOtherClass.getFootballController();

like:

        return getBaseballController();
        return someOtherClass.getFootballController();