小于1且大于0的值的计算百分比

Question

I am trying to display the percentage using BigDecimal.

for example if i have to do

    double val = (9522 / total ) * 100;

    System.out.println("Val is :" + val);

where total is 1200000.

I want to display the calculation as a percentage but since the calculation comes to a value less than 0 , I am unable to display the percentage

I also tried

    BigDecimal decimal = new BigDecimal((9522 * 100 ) / total);
    BigDecimal roundValue = decimal.setScale(2, BigDecimal.ROUND_HALF_UP);
    System.out.println("decimal: " + decimal);
    System.out.println("roundValue: " + roundValue);

but with the same result.

How can I display the percentage even if it is in Decimals?

Answer 1

The problem is you are doing integer division.

If you want fractional results, you need to do floating point division.

double val = (9522 / (double) total) * 100;

Casting one of your operands to a double will cause Java to perform the correct type of division instead of defaulting to integer division.

Answer 2

You have to inform Java that you want at least one of the numerator or denominator treated as a double, to make sure the result is a double.

This will work:

double val = ((double)9522 / total ) * 100;

System.out.println("Val is :" + val);

Answer 3

BigDecimal decimal = new BigDecimal((9522 * 100 ) / total);

This is not how you do operations on BigDecimal : by the time the BigDecimal is constructed, the precision is gone, because the calculation (9522 * 100 ) / total is done at compile time. That's why the result is the same as with integers: in fact, the entire calculation is done in integers.

Here is how you calculate with BigDecimal objects:

BigDecimal decimal = new BigDecimal(9522)
    .multiply(new BigDecimal(100))
    .divide(new BigDecimal(total));

Answer 4

If you divide two integer you will get the result truncated. Add a .0 so that it is converted to floating point, and then you will not get a truncated result

new BigDecimal((9522.0 / total) *100);

Answer 5

You may be missing a cast.

double val = (9522 / (double)total ) * 100;

System.out.println("Val is :" + val);

My suspect is that total is an int, and hence 9522/1200000 results in an integer, which is truncated to 0 because the operation implies that the result must be smaller than 1. If you convert total to double the result is going to be a double, and you will be able to retain the decimals.