线程“main”中的异常java.util.IllegalFormatConversionException：d！= java.lang.String [英] Exception in thread "main" java.util.IllegalFormatConversionException: d != java.lang.String

问题描述

我是Java的新手，我不确定如何解决我在尝试运行此代码时遇到的错误：

I'm new to Java and I'm not sure how to fix the error I'm getting when trying to run this code:

import java.util.Scanner;
public class P3_3 
{

    public static void main(String[] args) 
    {
        Scanner in = new Scanner(System.in);
        System.out.print("Please enter a number: ");
        int number = in.nextInt();
        if (number < 0) number *= -1;
        if (number >= 10 && number < 100)
        {
            number = 2;
        }
        else if (number >= 100 && number < 1000)
        {
            number = 3;
        }
        else if (number >= 1000 && number < 10000)
        {
            number = 4;
        }
        else if (number >= 10000 && number < 100000)
        {
            number = 5;
        }
        else if (number >= 100000 && number < 1000000)
        {
            number = 6;
        }
        else if (number >= 1000000 && number < 10000000)
        {
            number = 7;
        }
        else if (number >= 10000000 && number < 100000000)
        {
            number = 8;
        }
        else if (number >= 100000000 && number < 1000000000)
        {
            number = 9;
        }
        else
        {
            System.out.println("Number is greater than 10 billion.");
        }
        System.out.printf("%d has ", number + "digits.");
    }
}

我正在尝试打印多少位数字有，通过检查数字是> = 10，> = 100 等等...
我运行代码，我能够输入一个int但是一旦我输入它并按回车所有我得到它一个错误，似乎无法看到我做错了什么。任何人都可以开导我吗？

I'm trying to print how many digits the number has, by checking whether the number is >= 10, >= 100 and so on... I run the code and I'm able to input an int but once I input it and press enter all I get it an error and can't seem to see what I have done wrong. Can anyone enlighten me?

推荐答案

问题在于：

System.out.printf("%d has ", number + "digits.");

％d 格式说明符需要一个整数作为第二个参数传递给 printf ，但是通过连接数字和数字。 ，你实际上传递了一个字符串。

the %d format specifier requires an integer to be passed as second parameter to printf, but by concatenating number and "digits.", you actually passed a String.

固定版本：

System.out.printf("has %d digits ", number);

请注意，您不能同时打印原始数字和位数，因为您用另一个在数字变量中。也许使用两种不同的。

note that you cannot print both the original number and the number of digits, because you overwrote one with the other in the number variable. Maybe use two different ones.

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