How to divide down to decimals and not get zero in Java? [duplicate]

Question

double[] arrayName = new double[10]; 
arrayName[0] = (14/49)*100;

Trying to get percentage of two numbers, 14 / 49, and add results to an array. All it returns is 0.0. Same thing if I use float instead of double. New to Java.

Answer 1

Either cast the ints to double, or just use doubles.

For example:

double[] arrayName = new double[10]; 
resultValue[0] = (14.0/49.0)*100;

or:

double[] arrayName = new double[10]; 
resultValue[0] = ((double)14/49)*100;

Answer 2

How you see it:

(double/double)*double

How the JVM sees it

(int/int)*int

From the the JLS. int to double is a widening conversion. From §5.1.2:

Widening primitive conversions do not lose information about the overall magnitude of a numeric value.

[...]

Conversion of an int or a long value to float, or of a long value to double, may result in loss of precision-that is, the result may lose some of the least significant bits of the value. In this case, the resulting floating-point value will be a correctly rounded version of the integer value, using IEEE 754 round-to-nearest mode (§4.2.4).

If you replace one of those with a double literal (like adding .0 or cast one of them to double and you should get the result you expect.

Answer 3

Like this:

arrayName[0] = (14/49)*100.0; // put ".0" after any of the numbers

or this:

arrayName[0] = (double)(14/49)*100;