Java 如何检查零是正数还是负数？
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How do I check if a zero is positive or negative?
提问by e4lime
Is it possible to check if a floatis a positive zero (0.0) or a negative zero (-0.0)?
是否可以检查 afloat是正零 (0.0) 还是负零 (-0.0)？
I've converted the floatto a Stringand checked if the first charis a '-', but are there any other ways?
我已将 the 转换float为 aString并检查第一个char是否为 a '-'，但还有其他方法吗？
采纳答案by harold
Yes, divide by it. 1 / +0.0fis +Infinity, but 1 / -0.0fis -Infinity. It's easy to find out which one it is with a simple comparison, so you get:
是的，除以它。1 / +0.0f是+Infinity，但是1 / -0.0f是-Infinity。通过简单的比较很容易找出它是哪一个，因此您会得到：
if (1 / x > 0)
// +0 here
else
// -0 here
(this assumes that xcan only be one of the two zeroes)
（这假设x只能是两个零之一）
回答by Jesper
You can use Float.floatToIntBitsto convert it to an intand look at the bit pattern:
您可以使用Float.floatToIntBits将其转换为 anint并查看位模式：
float f = -0.0f;
if (Float.floatToIntBits(f) == 0x80000000) {
System.out.println("Negative zero");
}
回答by andre baresel
Definitly not the best aproach. Checkout the function
绝对不是最好的方法。签出功能
Float.floatToRawIntBits(f);
Doku:
独行：
/**
* Returns a representation of the specified floating-point value
* according to the IEEE 754 floating-point "single format" bit
* layout, preserving Not-a-Number (NaN) values.
*
* <p>Bit 31 (the bit that is selected by the mask
* {@code 0x80000000}) represents the sign of the floating-point
* number.
...
public static native int floatToRawIntBits(float value);
回答by assylias
The approach used by Math.minis similar to what Jesper proposes but a little clearer:
使用的方法Math.min类似于 Jesper 提出的方法，但更清晰一点：
private static int negativeZeroFloatBits = Float.floatToRawIntBits(-0.0f);
float f = -0.0f;
boolean isNegativeZero = (Float.floatToRawIntBits(f) == negativeZeroFloatBits);
回答by Kip
When a float is negative (including -0.0and -inf), it uses the same sign bit as a negative int. This means you can compare the integer representation to 0, eliminating the need to know or compute the integer representation of -0.0:
当浮点数为负数（包括-0.0和-inf）时，它使用与负整数相同的符号位。这意味着您可以将整数表示与 进行比较0，从而无需了解或计算 的整数表示-0.0：
if(f == 0.0) {
if(Float.floatToIntBits(f) < 0) {
//negative zero
} else {
//positive zero
}
}
That has an extra branch over the accepted answer, but I think it's more readable without a hex constant.
这在接受的答案上有一个额外的分支，但我认为它在没有十六进制常量的情况下更具可读性。
If your goal is just to treat -0 as a negative number, you could leave out the outer ifstatement:
如果您的目标只是将 -0 视为负数，则可以省略外部if语句：
if(Float.floatToIntBits(f) < 0) {
//any negative float, including -0.0 and -inf
} else {
//any non-negative float, including +0.0, +inf, and NaN
}
回答by Reuben Thomas
Double.equalsdistinguishes ±0.0 in Java. (There's also Float.equals.)
Double.equals在 Java 中区分 ±0.0。（还有Float.equals。）
I'm a bit surprised no-one has mentioned these, as they seem to me clearer than any method given so far!
我有点惊讶没有人提到这些，因为在我看来它们比迄今为止给出的任何方法都更清晰！
回答by Tridib
For negative:
对于否定：
new Double(-0.0).equals(new Double(value));
For positive:
对于阳性：
new Double(0.0).equals(new Double(value));
