Java程序错误：可能会丢失精度 [英] Java program error: possible loss of precision

问题描述

我想弄清楚为什么我在Java程序中出现这种精度错误的错误。

I am trying to figure out why I am getting this loss of precision error in my Java program.

这是错误：

error: possible loss of precision
         int digit = num/Math.pow(10,i-1)%10;
                                         ^
  required: int
  found:    double
1 error

这是for循环中的代码片段

This is the code clip inside a for loop

for(int i = 1; i<=String.valueOf(num).length(); i++)
{
    int digit = num/Math.pow(10,i-1)%10;
    //etc
}

我想将数字保持为整数变量，我试图在循环外声明数字，我也尝试将其转换为一个不起作用的整数。我确实尝试过这样做：

I want to keep digit as an integer variable, and I tried to declare digit outside the loop, and I also tried casting it into an integer which didn't work. I did try doing it as:

digit += num/Math.pow(10,i-1)%10; //with digit declare outside of loop

神奇地工作，但我不想增加它，而我希望它包含我以后可以使用的数字。这里有什么我想念的吗？请解释。

which worked magically, but I don't want to increment it, instead I want it to contain the digit which I can use for later. Is there something I'm missing here? Please explain.

推荐答案

我尝试按如下方式运行您的代码：

I tried to run your code as follows:

int digit = (int) (num/Math.pow(10,i-1)%10);

它按预期工作，即它遍历变量num的数字（我假设为int）。

And it worked as expected, i.e. it iterated through the digits of your variable num (which I assumed as int).

当你使用+ =运算符时，它不是因为魔法，而是因为自动类型提升。您可以在此处阅读更多相关信息： http：// docs.oracle.com/javase/specs/jls/se7/html/jls-5.html

When you use the += operator, it works not because of magic, but because of automatic type promotion. You can read more about it here: http://docs.oracle.com/javase/specs/jls/se7/html/jls-5.html

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