使用最多五位总数格式化双精度值,必要时舍入十进制数字 [英] Format double values using a maximum of five total digits, rounding decimal digits if necessary
问题描述
我有 double
值,我想将其转换为 String
值,并具有以下格式限制:
I have double
values which I would like to convert to String
values with the following format restrictions:
number_of_fraction_digits = max(0,5-number_of_integer_digits)
number_of_fraction_digits = max( 0, 5 - number_of_integer_digits )
基本上我想在可能的情况下将位数保持为5,必要时舍入十进制数字。例如:
Essentially I want to keep the number of digits to 5 if possible, rounding decimal digits if necessary. For example:
float String
-------------------------
1 1
100 100
100000 100000
99999 99999
99999.99 99999
9999.99 9999.9
999.99 999.99
23.34324 23.343
我研究过使用DecimalFormat 但据我所知,它并没有完全实现我所追求的目标。
I've looked into using DecimalFormat but as far as I can tell it doesn't quite accomplish what I'm after.
它允许使用 setMaximumFractionDigits()
设置最大小数位数,但据我所知,我必须计算整数个数数字,并自己执行上述计算。
It allows setting of the maximum number of decimal digits using setMaximumFractionDigits()
but as far as I can tell I would have to calculate the number of integer digits and perform the above calculation myself.
所以基本的问题是,是否有一种漂亮,干净的内置方式来格式化数字。
So the basic question is whether there is a nice, clean built-in way to format numbers in this way.
推荐答案
public class SignificantFormat {
public static String formatSignificant(double value, int significant)
{
MathContext mathContext = new MathContext(significant, RoundingMode.DOWN);
BigDecimal bigDecimal = new BigDecimal(value, mathContext);
return bigDecimal.toPlainString();
}
public static void main(String[] args) {
double[] data = { 1, 100, 100000, 99999, 99999.99, 9999.99, 999.99, 23.34324 };
for(double d: data){
System.out.printf("Input: %10s \tOutput: %10s\n", Double.toString(d), formatSignificant(d, 5));
}
}
}
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