percentage of two int?
I want to get two ints, one divided by the other to get a decimal or percentage. How can I get a percentage or decimal of these two ints? (I'm not sure if it is right.. I'm probably way off...) for example:
int correct = 25;
int questionNum = 100;
float percent = correct/questionNum *100;
This is how I thought I could do it, but it didn't work... I want to make the decimal (if there is one) into a percent out of 100 for example in this case it is %25. any ideas anyone?
Here is the correct code (thanks to Salvatore Previti!):
float correct = 25;
float questionNum = 100;
float percent = (correct * 100.0f) / questionNum;
(btw, I am making a project using this for a quiz checking program that is why I need the percentage or decimal)
Solution 1:
If you don't add .0f
it will be treated like it is an integer, and an integer division is a lot different from a floating point division indeed :)
float percent = (n * 100.0f) / v;
If you need an integer out of this you can of course cast the float
or the double
again in integer.
int percent = (int)((n * 100.0f) / v);
If you know your n value is less than 21474836 (that is (2 ^ 31 / 100)), you can do all using integer operations.
int percent = (n * 100) / v;
If you get NaN is because wathever you do you cannot divide for zero of course... it doesn't make sense.
Solution 2:
Two options:
Do the division after the multiplication:
int n = 25;
int v = 100;
int percent = n * 100 / v;
Convert an int
to a float
before dividing
int n = 25;
int v = 100;
float percent = n * 100f / v;
//Or:
// float percent = (float) n * 100 / v;
// float percent = n * 100 / (float) v;
Solution 3:
One of them has to be a float going in. One possible way of ensuring that is:
float percent = (float) n/v * 100;
Otherwise, you're doing integer division, which truncates the numbers. Also, you should be using double
unless there's a good reason for the float
.
The next issue you'll run into is that some of your percentages might look like 24.9999999999999% instead of 25%. This is due to precision loss in floating point representation. You'll have to decide how to deal with that, too. Options include a DecimalFormat to "fix" the formatting or BigDecimal to represent exact values.