Question

我的源代码如下我正在尝试创建一个程序，当我的用户输入A，C或D时，它将计算圆的面积直径和圆周。我只想根据用户输入返回正确的响应。我设法让所有三个人在我的第一个案例中早些时候回归，但是将它们分开却难以理解？

import java.util.Scanner;

public class Test {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("This program will determine the Area, Circumference or Diameter for a circle. Type A for area C for Circumference and D for Diameter"); // Prompt for user input of capitol character

        while (!sc.hasNext("[A-Z]+")) {
            System.out.println(sc.next().charAt(0) + " is not a capital letter! Non Alphanumeric values are not permitted."); // error response for any unnaceptable character A-Z is specified as the range of acceptable characters
        }

        char c = ' ';
        c = sc.next().charAt(0); // looking through user input at character at position 0

        switch (c) {

        case 'A':
            System.out.print("Enter the radius: "); //I am storing the entered radius in floating point
            float radius = sc.nextFloat();
            float area = ((float) Math.PI) * ((float)(radius * radius));
            System.out.printf("The area of the circle is: %.2f \n", area);
            break;

        case 'C':
            System.out.print("Enter the radius: "); //I am storing the entered radius in floating point
            float circumference = ((float)(Math.PI * 2 * radius));
            System.out.printf("The circumference of the circle is: %.2f \n", circumference);
            break;

        case 'D':
            System.out.print("Enter the radius: "); //I am storing the entered radius in floating point
            float diameter = ((float)(radius * 2));
            System.out.printf("The diameter of the circle is: %.2f \n", diameter);
            break;
        }
    }
}

Answer 1

您在float radius = sc.nextFloat();内定义并计算case 'A':，但在其他两种情况下使用radius。在一个开关中只执行一种情况（虽然没有掉落），因此，当你选择情况'C'或'D'时，半径变量永远不会被定义，你会得到一个错误。

要解决此问题，请在开关

之外定义并计算radius

...

float radius = sc.nextFloat();
switch (c) {

case 'A':
    System.out.print("Enter the radius: "); //I am storing the entered radius in floating point
    float area = ((float) Math.PI) * ((float)(radius * radius));
    System.out.printf("The area of the circle is: %.2f \n", area);
    break;

case 'C':
    System.out.print("Enter the radius: "); //I am storing the entered radius in floating point
    float circumference = ((float)(Math.PI * 2 * radius));
    System.out.printf("The circumference of the circle is: %.2f \n", circumference);
    break;

case 'D':
    System.out.print("Enter the radius: "); //I am storing the entered radius in floating point
    float diameter = ((float)(radius * 2));
    System.out.printf("The diameter of the circle is: %.2f \n", diameter);
    break;
}
...

Java混淆初始化不同情况下的变量

1 个答案: