問題描述

我想將我作為字符串獲得的一些數字轉換為雙精度數，但這些數字不在美國標準語言環境中，而是在不同的語言環境中.我該怎么做?

I want to convert some numbers which I got as strings into Doubles, but these numbers are not in US standard locale, but in a different one. How can I do that?

推薦答案

試試 java.text.NumberFormat.來自 Javadocs:

Try java.text.NumberFormat. From the Javadocs:

要為不同的區域設置格式化數字，請在調用 getInstance 時指定它.

To format a number for a different Locale, specify it in the call to getInstance.

NumberFormat nf = NumberFormat.getInstance(Locale.FRENCH);

您還可以使用 NumberFormat 來解析數字:

You can also use a NumberFormat to parse numbers:

myNumber = nf.parse(myString);

parse() 返回一個 編號;所以要獲得一個double，你必須調用myNumber.doubleValue():

parse() returns a Number; so to get a double, you must call myNumber.doubleValue():

    double myNumber = nf.parse(myString).doubleValue();

請注意，parse() 永遠不會返回 null，因此這不會導致 NullPointerException.相反，如果失敗，parse 會拋出一個檢查過的 ParseException.

Note that parse() will never return null, so this cannot cause a NullPointerException. Instead, parse throws a checked ParseException if it fails.

我最初說還有另一種方法可以轉換為double:將結果轉換為Double并使用拆箱.我認為由于使用了 NumberFormat 的通用實例(根據 getInstance)，它總是返回一個 Double.但是 DJClayworth 指出 parse(String, ParsePosition)(由 parse(String) 調用)表示如果可能返回一個 Long.因此，將結果轉換為 Double 是不安全的，不應嘗試！
謝謝，DJClayworth！

I originally said that there was another way to convert to double: cast the result to Double and use unboxing. I thought that since a general-purpose instance of NumberFormat was being used (per the Javadocs for getInstance), it would always return a Double. But DJClayworth points out that the Javadocs for parse(String, ParsePosition) (which is called by parse(String)) say that a Long is returned if possible. Therefore, casting the result to Double is unsafe and should not be tried!
Thanks, DJClayworth!

這篇關于如何使用特定語言環境在 Java 中將 String 轉換為 Double?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！