Java 上 0.1 到 2 的奇怪循环 [英] Strange loop on Java for 0.1 to 2

问题描述

我尝试从 0.1 循环到 2.0，然后将输出打印到控制台..但我得到了如下奇怪的输出:

<前>0.10.20.300000000000000040.40.50.60.70.79999999999999990.89999999999999990.99999999999999991.09999999999999991.21.31.40000000000000011.50000000000000021.60000000000000031.70000000000000041.80000000000000051.90000000000000062.0000000000000004

源代码:

公共类测试{public static void main(String[] a) {双 i = 0.1;而 (i <2.1)System.out.println(i);i+=0.1;}}}

为什么它不打印确切的数字，而不是像 0.79999999999 这样的点?使用 for 而不是 while 也有什么区别，因为我不知道如何进行 0.1 增量?

解决方案

这是正常的.它是浮点固有的；像 0.3 这样的数字不能以二进制形式存储为精确值，因此您会慢慢累积错误.参考资料:Python 手册、维基百科，普林斯顿CS的技术解释一>.

I tried to loop from 0.1 to 2.0 and then print the output to the console.. But I got strange output like these:

0.1
0.2
0.30000000000000004
0.4
0.5
0.6
0.7
0.7999999999999999
0.8999999999999999
0.9999999999999999
1.0999999999999999
1.2
1.3
1.4000000000000001
1.5000000000000002
1.6000000000000003
1.7000000000000004
1.8000000000000005
1.9000000000000006
2.0000000000000004

Source code:

public class test {
    public static void main(String[] a) {
        double i = 0.1;
        while (i < 2.1)
            System.out.println(i);
            i+=0.1;
        }
    }
}

Why it doesn't this print the exact numbers instead of having point like 0.79999999999? Also is ther any difference using for instead of while, since I dont know how to make 0.1 increment?

解决方案

This is normal. It's inherent in floating point; numbers like 0.3 can't be stored as exact values in binary, so you get slowly accumulating errors. References: Python manual, Wikipedia, Technical explanation from Princeton CS.

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