在Java中使用浮点型或双精度输出十进制数（Eclipse）

Question

I wanted the output to be 0.123456789123456789 . But, result is 0.123456789 in float type. 0.12345678912345678 in double type. So, I tried using %030.19f,e but this doesn't work either. How do I output 0.123456789123456789 ?

Answer 1

For bigger numbers you can use BigDecimal. For example:

import java.math.BigDecimal;

public class HelloWorld{

 public static void main(String []args){
    BigDecimal bdcm=new BigDecimal("0.123456789123456789");
    System.out.println(bdcm);
    BigDecimal bdcm2=new BigDecimal("100.123456789123456789");
    System.out.println(bdcm.add(bdcm2));
 }
}

And the output is proper :)

Answer 2

Don't use float or double if you need to print exact values.

Use instead a BigDecimal that is a class to hold

Immutable, arbitrary-precision signed decimal numbers

The problem using float and double is that they suffer for the rounding related to binary decimal numbers.