Question

我正在进行Java分配，每当我在扫描仪中插入小数时，代码都会返回错误。我走得足够远，意识到它不是因为数字是小数，而是因为每当输入任何不是数字的字符时都会返回此错误。

Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Unknown Source)
    at java.util.Scanner.next(Unknown Source)
    at java.util.Scanner.nextInt(Unknown Source)
    at java.util.Scanner.nextInt(Unknown Source)
    at population.main(population.java:14)

如果有人可以帮助我获得小数点，那将是很酷的，这是我的错误代码。

import java.util.Scanner;

public class population {

    public static void main(String[] args) {
        System.out.print("Enter the amount of years:"); // Prompts the user
        Scanner input = new Scanner(System.in); // Defines the scanner
        double value = input.nextInt(); // Defines the variable


        double A = (60.0 * 24.0 * 365.0); // Brings time from seconds to years
        double B = ((60.0 / 7.0) * A); // Births per year
        double C = ((60.0 / 13.0) * A); // Deaths per year
        double D = ((60.0 / 45.0) * A); // Immigration per year
        double E = (B + D - C); // Change per year  
        double F = ((E * value) + 312032486.0); // Change in population after 5 years

        System.out.println(F);

    }

}

Answer 1

input.nextInt();接受整数。将其更改为input.nextDouble()

Answer 2

Scanner#nextInt() - 将输入的下一个标记扫描为int。

并抛出 InputMismatchException - 如果下一个标记与Integer正则表达式不匹配，或者超出范围

input.nextInt()接受int

类型的输入

使用

input.nextDouble()

Answer 3

由于输入无效而发生异常。你可以添加try catch块。请参阅以下代码。
有关详细信息，请参阅this

public static void main(String[] args) {
    try
    {
        System.out.print("Enter the amount of years:"); // Prompts the user
        Scanner input = new Scanner(System.in); // Defines the scanner
        double value = input.nextInt(); // Defines the variable
        double A = (60.0 * 24.0 * 365.0); // Brings time from seconds to years
        double B = ((60.0 / 7.0) * A); // Births per year
        double C = ((60.0 / 13.0) * A); // Deaths per year
        double D = ((60.0 / 45.0) * A); // Immigration per year
        double E = (B + D - C); // Change per year  
        double F = ((E * value) + 312032486.0); // Change in population after 5 years
        System.out.println(F);
    }
    catch(Exception e)
    {
        System.out.println("Invalid Input");
    }
}

在Java中使用扫描仪

3 个答案: