BowlingBallFactory

BowlingBallFactory.groovy

class BowlingBallFactory {
    static private class BowlingBall implements IBowlingBall{
        private String petName;

        BowlingBall() {
        }

        private void setPetName(String petName) {
            this.petName = petName;
        }

        String getPetName() {
            return this.petName;
        }
    }

    IBowlingBall createBowlingBallFor(Bowler b) {
        b.setBowlingBall(new BowlingBall());
    }

    IBowlingBall createBowlingBallFor(ProShop p) {
        p.addBowlingBall(new BowlingBall());
    }

}

class Bowler {
    private BowlingBall bowlingBall;

    Bowler(BowlingBall b) {
        this.bowlingBall = b;
    }

    void setPetName(String petName) {
        if (petName ==~ /[A-Z][a-z\s]*/) {
            bowlingBall.setPetName(petName);
        } else {
            throw Exception("only letters, please")
        }
    }

    String getPetName() {
        return bowlingBall.getPetName();
    }
}