Java arithmetics for calculating a percentage

Question

I have a little problem in my java application.

I have to calculate the score they have when they finish, I use this method:

public Float ScoreProcent(in         


        

Answer 1

Firstly, you shouldn't be using Float all over the place - you want float; there's no need to be boxing here.

Secondly, you're not using x and y at all.

Thirdly, I'd say the way you're expressing the equation is at the least confusing. It's possible that just changing to x and y would be fine, but I wouldn't - I'd change the whole way you're expressing yourself.

Fourthly, you're violating Java naming conventions by writing a method name in PascalCase. You've also got a spelling mistake.

Fixing all of these, you'd end with with something like:

public static float getPercentageCorrect(int questions, int correct) {
    float proportionCorrect = ((float) correct) / ((float) questions);
    return proportionCorrect * 100;
}

I'd actually generalize this - it's not specific to "correct answers", so can be used for anything where it's some score out of a total:

/**
 * Returns a proportion (n out of a total) as a percentage, in a float.
 */
public static float getPercentage(int n, int total) {
    float proportion = ((float) n) / ((float) total);
    return proportion * 100;
}

As noted in comments, this could be written as:

float proportion = (float) n / total;

... but then you need to know the precedence rules to validate it. I've included both casts explicitly to make it clear that I want to convert each operand to float before the division.