(Java) 为什么我的代码没有打印出完整的数字？

Question

I'm trying to calculate the value of e using the following Java code:

import java.util.Scanner;

public class Test {
    public static void main(String[] args) {
        Scanner scnr = new Scanner(System.in);
        
        int n;
        
        System.out.print("number of values: ");
        n = scnr.nextInt();
        
        double e = 0.0;
        double f = 1.0;
        for (int i = 1; i <= n; i++) {
            f = f * (i);
            e += 1 / f;
        }
        e += 1;
        System.out.print(e);
    }
}

However, when I print out e, the number it limited to 2.7182818284590455 instead of a much more specific number (2.7182818284590455 x 10^-308 or something similar). Is it a problem with the Types I'm using?

Answer 1

From this answer :

The number of decimal places in a double is 16 .

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I can't see how you expect to get 2.7182818284590455 x 10^-308 :

0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000027182818284590455

That's a very small fraction!

What you're doing is adding an increasingly smaller fraction to e . Based on your code, you can only expect the result to be between 2.0 and 3.0 .

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What you probably were looking for was a precision of more than 16 decimal places. That simply can't be achieved using double due to precision limitations.