如何在 java 中设置双原始类型的特定位数？

Question

I want a particular number of digits (before decimal + after decimal) in double primitive type.

Is there any way to do this...

For eg: (fixed to 6 digits)

1. If we have 12.666666667 gives output as 12.6667
2. If we have 5.6666666667 gives output as 5.66667
3. But , If we have 9.00000000 gives output as only 9.

For, more clear understanding, I have attached an image. enter image description here

Answer 1

Two things to consider. One is if you need an exact precision, since floating point arithmetic might not give you that. See the BigDecimal class for more information. The other is what you're trying to do: display a number with a certain number of decimal places. You can accomplish this with String.format . For example

double num = 5.666666666;
String formatted = String.format("%.5f", num);

And

System.out.println(formatted)

Will output

5.66667

Answer 2

import java.text.DecimalFormat;

public class rounding {
    public static void main(String[] args) {
        double num = 23.122345899;
        double rounded = Math.round(num * 1000000) / 1000000.0;
        System.out.println(rounded);
    }
}