Java双除正

Question

为什么这个java代码产生正无穷大？

    double d = 10.0 / -0; 

    System.out.println(d);
    if (d == Double.POSITIVE_INFINITY) 
        System.out.println("Positive Infinity");
    else 
        System.out.println("Negative Infinity");

Answer 1

虽然 double区分正负零，int才不是。因此，当您转换 int 时值为 0 到 double ，你总是得到“正零”。-0是 int ，其值为 0。
除以“负零”得到负无穷大。为此，您需要将除数指定为 double (不是 int ):

    double d = 10.0 / -0.0;

    System.out.println(d);
    if (d == Double.POSITIVE_INFINITY) {
        System.out.println("Positive Infinity");
    } else {
        System.out.println("Different from Positive Infinity");
    }
    if (d == Double.NEGATIVE_INFINITY) {
        System.out.println("Negative Infinity");
    } else {
        System.out.println("Different from Negative Infinity");
    }

输出:

-Infinity
Different from Positive Infinity
Negative Infinity