Java：BigDecimal 和 Double.NaN
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Java: BigDecimal and Double.NaN
提问by Denis Kulagin
I am trying to execute following code:
我正在尝试执行以下代码：
import java.math.*;
public class HelloWorld{
public static void main(String []args){
System.out.println(BigDecimal.valueOf(Double.NaN));
}
}
And reasonably, I am getting:
并且合理地，我得到：
Exception in thread "main" java.lang.NumberFormatException
at java.math.BigDecimal.<init>(BigDecimal.java:470)
at java.math.BigDecimal.<init>(BigDecimal.java:739)
at java.math.BigDecimal.valueOf(BigDecimal.java:1069)
at HelloWorld.main(HelloWorld.java:6)
Is there a way to represent Double.NaNin BigDecimal?
有没有办法在 BigDecimal 中表示Double.NaN？
回答by Stephen C
Is there a way to represent Double.NaN in BigDecimal?
有没有办法在 BigDecimal 中表示 Double.NaN？
No. The BigDecimalclass provides no representation for NaN, +∞ or -∞.
不。BigDecimal该类不提供 NaN、+∞ 或 -∞ 的表示。
You might consider using null... except that you need at least 3 distinct nullvalues to represent the 3 possible cases, and that is not possible.
您可能会考虑使用null... ，但您需要至少 3 个不同的null值来表示 3 种可能的情况，这是不可能的。
You could consider creating a subclass of BigDecimalthat handles these "special" values, but it may be simpler to implement your "numbers" as a wrapper for BigDecimal, and treat NaNand the like as special cases; e.g.
您可以考虑创建一个BigDecimal处理这些“特殊”值的子类，但将“数字”实现为 的包装器可能更简单BigDecimal，NaN并将其视为特殊情况；例如
public class MyNumber {
private BigDecimal value;
private boolean isNaN;
...
private MyNumber(BigDecimal value, boolean isNaN) {
this.value = value;
this.isNaN = isNan;
}
public MyNumber multiply(MyNumber other) {
if (this.isNaN || other.isNaN) {
return new MyNumber(null, true);
} else {
return new MyNumber(this.value.multiply(other.value), false);
}
}
// etcetera
}
回答by atish shimpi
"NaN" stands for "not a number". "Nan" is produced if a floating point operation has some input parameters that cause the operation to produce some undefined result. For example, 0.0 divided by 0.0 is arithmetically undefined. Taking the square root of a negative number is also undefined.
“NaN”代表“非数字”。如果浮点运算具有一些导致运算产生某些未定义结果的输入参数，则会产生“Nan”。例如，0.0 除以 0.0 在算术上是未定义的。取负数的平方根也是未定义的。
BigDecimal.valueOf(Double.NaN)It trying to convert Double.NaNto BigDecimal, and result is number can not be converted in to BigDecimali.e. java.lang.NumberFormatException.
BigDecimal.valueOf(Double.NaN)它试图转换Double.NaN为BigDecimal，结果是数字无法转换为BigDecimalie java.lang.NumberFormatException。
回答by wastl
According to the docs it is not possible, see http://docs.oracle.com/javase/7/docs/api/java/math/BigDecimal.html#BigDecimal%28double%29
根据文档，这是不可能的，请参阅http://docs.oracle.com/javase/7/docs/api/java/math/BigDecimal.html#BigDecimal%28double%29
回答by Amr
NaN = not a number. Its not a number, so it cant be converted to BigDecimal
NaN = 不是数字。它不是数字，因此无法转换为 BigDecimal
回答by Stephan
You can rewrite your code like this:
你可以像这样重写你的代码：
public static void main(String []args){
Double d = ...;
String value;
if (Double.isNaN(d) == true) {
value= "My-NaN-formatting";
} else {
value=BigDecimal.valueOf(d);
}
System.out.println(value);
}
