使用 DecimalFormat 显示填充零

Show padding zeros using DecimalFormat(使用 DecimalFormat 显示填充零)

问题描述

我正在使用 DecimalFormat 将双精度数设置为 2 位小数，如下所示:

I'm using DecimalFormat to format doubles to 2 decimal places like this:

DecimalFormat dec = new DecimalFormat("#.##");
double rawPercent = ( (double)(count.getCount().intValue()) / 
                            (double)(total.intValue()) ) * 100.00;
double percentage = Double.valueOf(dec.format(rawPercent));

它有效，但如果我有一个像 20 这样的数字，它会给我这个:

It works, but if i have a number like 20, it gives me this:

20.0

我想要这个:

20.00

有什么建议吗?

推荐答案

DecimalFormat 类用于将十进制数值转换为字符串.在您的示例中，您正在获取来自 format() 方法的字符串并将其放回双变量中.如果您随后输出该双变量，您将看不到格式化的字符串.请参阅下面的代码示例及其输出:

The DecimalFormat class is for transforming a decimal numeric value into a String. In your example, you are taking the String that comes from the format( ) method and putting it back into a double variable. If you are then outputting that double variable you would not see the formatted string. See the code example below and its output:

int count = 10;
int total = 20;
DecimalFormat dec = new DecimalFormat("#.00");
double rawPercent = ( (double)(count) / (double)(total) ) * 100.00;

double percentage = Double.valueOf(dec.format(rawPercent));

System.out.println("DF Version: " + dec.format(rawPercent));
System.out.println("double version: " + percentage);

哪些输出:

"DF Version: 50.00"
"double version: 50.0"

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