DecimalFormat无法正确舍入到小数点后两位

Question

In the program I am writing I have a percent change function. With the numbers I'm using, it is supposed to return .03, yet I just get 0. Using a calculator, the value not formatted would be 0.03303. I want the number to be truncated after the second decimal place, no rounding at all.

df = new DecimalFormat("###.##;-###.##");
df.setRoundingMode(RoundingMode.DOWN);

//later in code
return df.format(((price-base_price)/price)*100.00D);

Edit: all variable types are doubles. Base price is 756.60 and price is 756.85

Answer 1

Your assumption about the value calculated in ((price-base_price)/price)*100.00D is incorrect (I think you've probably invoked integer math, try ((price-base_price)/(double)price)*100.00D ). When I directly execute,

double value = 0.03303;
DecimalFormat df = new DecimalFormat("###.##;-###.##");
df.setRoundingMode(RoundingMode.DOWN);
System.out.println(df.format(value));

I get the (requested) output

0.03