What decides Nan and Infinity in java division operations

问题

Output of the below code confusing me. Why NaN sometimes and Infinity other times ?

public static void main (String[] args) {

    double a = 0.0;
    double b = 1.0;
    int c = 0; 
    System.out.println(a/0.0);
    System.out.println(a/0);
    System.out.println(b/0.0);
    System.out.println(b/0);
    System.out.println(c/0.0);
    System.out.println(c/0);
}

Outputs is:

NaN
NaN
Infinity
Infinity
NaN
Exception in thread "main" java.lang.ArithmeticException: / by zero

What is the deciding factor here ?

回答1:

This is because of The IEEE Standard for Floating-Point Arithmetic (IEEE 754) which is a technical standard for floating-point computation established in 1985 by the Institute of Electrical and Electronics Engineers (IEEE).

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The purpose:

The IEEE floating-point standard,.. specifies that every floating point arithmetic operation, including division by zero, has a well-defined result. The standard supports signed zero, as well as infinity and NaN (not a number). There are two zeroes: +0 (positive zero) and −0 (negative zero) and this removes any ambiguity when dividing.

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The Rule:

In IEEE 754 arithmetic, a ÷ +0 is positive infinity when a is positive, negative infinity when a is negative, and NaN when a = ±0.

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Source

来源：https://stackoverflow.com/questions/51801054/what-decides-nan-and-infinity-in-java-division-operations