初始化一个double和它的getter

Question

What benefits has the following?

private double pro;
pro = Double.NaN;

Why not make it

pro = 0.0;

the getter is:

public double getpro() {
    if (Double.isNaN(pro))
        somemethod();
    return pro;
}

Answer 1

Because NanN stands for "not a number," it is generally a hint that the number hasn't been initialized.

You could use pro = 0.0; and that would be fine, too. I think that the issue is more of a style-thing.

Answer 2

Because any operation on NaN results NaN. While operations with 0.0 may result as if pro is set to some value. While NaN may be used to represents that pro isn't defined yet as your case.

     Double d =Double.NaN;
     System.out.println(d*10);
     System.out.println(10/d);
     System.out.println(d/10);
     System.out.println(d+10);

results

NaN
NaN
NaN
NaN

while d=0.0 would result something like

0.0
Infinity
0.0
10.0

Answer 3

我想在你的情况下， NaN是一个提示，因为变量pro没有被初始化，0.0是一个有效的初始化值。