Updating Java object attribute incorrectly?

Question

EDIT: Please see edit towards bottom

I have the following class:

public class Player { 
        SingleGameRound roundOne = new SingleGameRound(); 
        float score = 0.0; 
         
        <constructor> 
         
        public String toString() { 
                float roundScore = this.roundOne.getScore(); 
                this.score = roundScore; 
                return "";
        }
        
        public float getResult() {
                return this.score;
        }            
}

I'm trying to update this class's score attribute with the value returned by getScore() (a method belonging to a different public class singleGameRound).

However, after instantiating a Player object and calling the getResult() method on it, the default value of score is returned instead of an updated value. It seems like score never gets updated.

I tried using a setter method to update the attribute but the same thing happened too. Am I updating the attribute incorrectly? TIA!

(note: my actual code doesn't look like this exactly but generally follows this structure)

---

EDIT 1) After going back to the code for the SingleGameRound class, I decided to make some changes.

Before, this class would also utilise an adapted toString() method to calculate the score of a single game round - however, this score wasn't stored anywhere (it would just be returned in a string).

I've added an attribute to the SingleGameRound class so that it can store the calculated score value. My code for that class now looks like this:

public class SingleGameRound { 
        private float roundScore = 0.0f; 
         
        <constructor> 
         
        public String toString() { 
                float score = *some calculations*
                this.roundScore = score;
                String resultLine = "You scored " + this.roundScore;
                return resultLine;
        }
        
        public float getScore() {
                return this.roundScore;
        }            
}

Now, if I create an object of SingleGameRound and do System.out.println(SingleGameRoundObj), I get e.g. >>> You scored 10.5

But if I do System.out.println(SingleGameRoundObj.getScore()), I just get >>> 0.0. My original problem still exists, the values of my attributes aren't updating in either class.

(Apologies for all the faff and many thanks if you made it this far, sincerely)