使用 Double 的线程“主”java.util.InputMismatchException 中的异常

Question

import java.util.Scanner;
import java.text.DecimalFormat;

public class palomba2 {

    public static void main(String args[]) {

        Scanner keyboard = new Scanner(System.in);
        //allows input to be read
        // VOLUME OF A PRISM

        int prLngth, prWdth, prHght, prVol;

        System.out.print("Enter the length of the prism in feet: ");
        prLngth = keyboard.nextInt();

        System.out.print("Enter the width of the prism in feet: ");
        prWdth = keyboard.nextInt();

        System.out.print("Enter the height of the prism in feet: ");
        prHght = keyboard.nextInt();

        prVol = prLngth * prWdth * prHght;

        System.out.print("The volume of the prism is " + prVol);
        System.out.print(" feet.");
        System.out.println("");
        System.out.println("");
        // AREA/CIRCUMFERENCE OF A CIRCLE

        DecimalFormat format = new DecimalFormat("0.##");

        double radius, circ, area;

        System.out.print("Enter the radius of a circle rounded to the nearest hundreth: ");
        radius = keyboard.nextInt();

        circ = 2 * radius * 3.14159265358979;
        area = radius * radius * 3.14159265358979;

        System.out.print("The circumference of the circle is " + format.format(circ));
        System.out.print("units.");
        System.out.print("The area of the circle is " + format.format(area));
        System.out.print("units.");
    }
}

在我输入圆的半径之前，我的代码中的所有内容都有效。输入半径后出现错误消息。

 Enter the radius of a circle rounded to the nearest hundreth: 2.12

 Exception in thread "main" java.util.InputMismatchException
     at java.base/java.util.Scanner.throwFor(Scanner.java:860)
     at java.base/java.util.Scanner.next(Scanner.java:1497)
     at java.base/java.util.Scanner.nextInt(Scanner.java:2161)
     at java.base/java.util.Scanner.nextInt(Scanner.java:2115)
     at palomba2.main(palomba2.java:52)

Answer 1

您键入了一个双变量 2.12 但试图将其读取为 int ：输入不匹配 -> InputMismatchException

---

另外，变量radius 的类型是double，所以你不能给它一个int 值（你也需要：

• radius = keyboard.nextDouble();

---

但最好使用radius = Double.parseDouble(keyboard.nextLine()) 来消耗返回字符（int 相同：int val = Integer.parseInt(keyboard.nextLine())

Answer 2

你只需要改变：

radius = keyboard.nextInt();

到：

radius = keyboard.nextDouble();

因为变量radius 被声明为double 它应该是这样的：

double radius, circ, area;
System.out.print("Enter the radius of a circle rounded to the nearest hundreth: ");
radius = keyboard.nextDouble();