如何格式化给定语言环境的双精度值和小数位数？ [英] How to format double value for a given locale and number of decimal places?

问题描述

如何使用 NumberFormat 格式化给定区域设置<的 double 值/ code>（默认语言环境已足够）和给定的小数位数？

How can I use NumberFormat to format a double value for a given Locale (default locale is sufficient) and for a given number of decimal places?

例如，我有以下值：

double d1 = 123456.78;
double d2 = 567890;

我想以下列方式打印它们，例如使用美国语言环境和2位小数：

And I want to print them in the following way, for example with US locale and 2 decimal places:

123,456.78
567,890.00

在这种情况下，我实际上并不关心舍入模式，因为这些双值是从具有给定比例的 BigDecimal 获得的，所以它们的小数位数总是小于或等于我想要打印的小数位数。

I don't actually care about rounding mode in this case, because these double values are gained from a BigDecimal with the given scale, so their number of decimal places is always lesser or equal than the number of decimal places I want to print.

编辑：

为了使事情更加明确，问题在于我想以依赖于语言环境的方式显示货币，但是具有固定的小数位数。上面的示例显示了如果系统区域设置为 en_US ，应如何格式化值。现在假设，系统区域设置是 cs_CZ （捷克语），因此应该以这种方式格式化相同的数字：

To make things a bit more clear, the thing is that I want to display money in a locale dependent way, but with a fixed number of decimal places. The example above showed, how the values should be formatted if the system locale is en_US. Now lets say, the system locale is cs_CZ (Czech), so the same numbers should be formatted in this way:

123 456,78
567 890,00

现在，如何设置NumberFormat以始终显示2个小数位，但是根据当前区域设置显示千位分隔符和小数点？

Now, how can I set up a NumberFormat to always display 2 decimal places, but to display thousands separator and decimal point based on the current locale?

推荐答案

如果您想阅读NumberFormat的文档，解决方案将是显而易见的：

If you care to read NumberFormat's documentation, the solution would be obvious:

double d1 = 123456.78;
double d2 = 567890;
// self commenting issue, the code is easier to understand
Locale fmtLocale = Locale.getDefault(Category.FORMAT);
NumberFormat formatter = NumberFormat.getInstance(fmtLocale);
formatter.setMaximumFractionDigits(2);
formatter.setMinimumFractionDigits(2);
System.out.println(formatter.format(d1));
System.out.println(formatter.format(d2));
System.out.println(fmtLocale.toLanguageTag());

在我的机器上打印出来：

On my machine this prints out:

123 456,78

567 890,00

pl-PL

123 456,78
567 890,00
pl-PL

我相信这就是你要找的东西，你不必弄乱模式。我不这样做 - 例如，有一些区域设置将数字分组，而不是三组（这就是我们讨论分组分隔符和不 的原因）千位分隔符）。

I believe this is what you are looking for, and you don't have to mess-up with patterns. I wouldn't do that - for instance there are locales which group digits by two, not by three (this is the reason we talk about grouping separator and not thousands separator).

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