科学计数到小数 [英] Scientific notation to decimal
问题描述
我有一个双精度字,我正在尝试将其转换为十进制数。当我使用十进制格式实现此目标时,我得到以下信息:
I have a double and i am trying to convert it to a decimal. When i use decimalformat to achieve this i get the following:
public void roundNumber(){
double d = 2.081641999208976E-4;
JOptionPane.showMessageDialog(null,roundFiveDecimals(d));
}
public double roundFiveDecimals(double d) {
DecimalFormat df = new DecimalFormat("#.#####");
return Double.valueOf(df.format(d));
}
我希望输出为.00021;但是,我得到2.1E-4。谁能帮助解释如何获取.00021而不是2.1E-4?
I want the output to be .00021; however, i get 2.1E-4. Can anyone help explain how to get .00021 and not 2.1E-4?
推荐答案
您正在解析<来自 DecimalFormat
的结果-您应该以 String
的形式返回:
You're parsing the result from DecimalFormat
- you should be returning it as a String
:
public String roundFiveDecimals(double d) {
DecimalFormat df = new DecimalFormat("#.#####");
return df.format(d);
}
double
的值本身没有格式的概念-只是一个数字。 DecimalFormat
的工作是将值格式化为文本,但是您需要...如果将文本 back 转换为数字,则已经失去了这项工作。
The double
value itself has no concept of formatting - it's just a number. It's the job of DecimalFormat
to format the value into text however you want... if you then convert that text back into a number, you've lost that work.
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