java - 了解 float 计数器

Question

我有以下简单代码:

for (float i=0; i<1f; i+=0.1) {
    System.out.println(i);
}

我刚刚得到以下结果:

0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.70000005
0.8000001
0.9000001

但我不明白为什么会有。拜托，我希望你能告诉我。谢谢。

Answer 1

来自 The Floating-Point Guide :

Why don’t my numbers, like 0.1 + 0.2 add up to a nice round 0.3, and instead I get a weird result like 0.30000000000000004?

Because internally, computers use a format (binary floating-point) that cannot accurately represent a number like 0.1, 0.2 or 0.3 at all.

When the code is compiled or interpreted, your “0.1” is already rounded to the nearest number in that format, which results in a small rounding error even before the calculation happens.