Question

I’d like to call a method that either returns false, or an integer. At the moment my code is:

int winningID = -1;
if((ID = isThereAWinner()) != -1) {
    // use the winner's ID
} else {
    // there's no winner, do something else
}

private int isThereAWinner() {
    // if a winner is found
    return winnersID;
    // else
    return -1;
}

I don’t like the if((ID = isThereAWinner()) != -1) bit as it doesn’t read very well, but unlike C you can’t represent booleans as integers in Java. Is there a better way to do this?

Answer 1

I would use something similar to Mat’s answer:

class Result {
    public static Result withWinner(int winner) {
        return new Result(winner);
    }

    public static Result withoutWinner() {
        return new Result(NO_WINNER);
    }

    private static final int NO_WINNER = -1;

    private int winnerId;

    private Result(int id) {
        winnerId = id;
    }

    private int getWinnerId() {
        return winnerId;
    }

    private boolean hasWinner() {
        return winnerId != NO_WINNER;
    }
}

This class hides the implementation details of how you actually represent if there were no winner at all.

Then in your winner finding method:

private Result isThereAWinner() {
    // if a winner is found
    return Result.withWinner(winnersID);
    // else
    return Result.withoutWinner();
}

And in your calling method:

Result result = isThereAWinner();
if(result.hasWinner()) {
    int id = result.getWinnerId();
} else {
    // do something else
}

It may seem a little bit too complex, but this approach is more flexible if there would be other result options in the future.