CODEWITHSUNDEEP
javamath
user3968848
user3968848

Reputation: 119

Why is answer Zero for division?

Within my Activity I am attempting to divide two values then multiply them by 100 in order to give a percentage score.

My issue is that the percentage score is always zero, even though this is impossible with the values I am using.

What am I doing wrong?

Declaring the 2 variables at start of activity:

int score = 0;
int totalQuestions=0;

Onclick logic showing how they are calculated:

public void onClick(View v) {

        if (checkForMatch((Button) v)) {
            //increment no of questions answered (for % score)
            totalQuestions++;
            //increment score by 1
            score++;

        } else {
            //increment no of questions answered (for % score)
            totalQuestions++;

        }

    }


public void writeToDatabase() {
        // create instance of databasehelper class
        DatabaseHelper db = new DatabaseHelper(this);

        int divide = (score/ totalQuestions );

        int percentageScore = (divide * 100);

        Log.d("Pertrace", "per score "+ percentageScore);
        Log.d("divide", "divide "+ divide);


        // Adding the new Session to the database
        db.addScore(new Session(sessionID, "Stroop", SignInActivity
                .getUserName(), averageMedLevel, medMax, averageAttLevel,
                attMax, percentageScore, myDate, "false", fileNameRaw, fileNameEEGPower, fileNameMeditation, fileNameAttention));

        // single score, used for passing to next activity
        single = db.getScore(sessionID);

    }

Note: from my Trace logs i can see that is it the int divide that is zero, why would this be the case considering that score and totalQuestions are always greater than zero? E.g. 20 and 25.

Upvotes: 1

Views: 134

Answers (4)

Rahul Tripathi
Rahul Tripathi

Reputation: 172378

The reason is this line

int divide = (score/ totalQuestions);

You are dividing the numbers and storing in an int.

You need to store in a double

double divide = (double)score / totalQuestions;

If you want the result as int

double divide = (double)score / totalQuestions;
int percentageScore = (int) Math.ceil(divide * 100);

Upvotes: 2

Elliott Frisch
Elliott Frisch

Reputation: 201399

You are performing integer division. First cast score to a double (so you get floating point math), then I would use Math.round() to round the result of the multiplication. For example,

int score = 3;
int totalQuestions = 4;
double divide = ((double) score / totalQuestions);
int percentageScore = (int) Math.round(divide * 100);
System.out.println(percentageScore);

Output is the expected

75

Upvotes: 1

ata
ata

Reputation: 9011

You are saving them in int. Save values in float or double.

Also, when division occurs, the intermediate result is saved in one of the variable that is used in division. If that is an int, it will be truncated before being saved in double. So do something like double divide = (double)score * totalQuestions

Upvotes: 2

Sean Owen
Sean Owen

Reputation: 66866

The operands need to be float or double, and so does the variable you put it in:

double divide = (double) score/ totalQuestions;

Upvotes: 0

Related Questions