将字符串转换为双精度二进制错误

Question

这是我的代码，我正在尝试将字符串“ pizza”与双精度“ subTotal”相乘。 Java不喜欢这样。

import java.util.Scanner;

public class Main {
   public static void main(String[] args) {

     Scanner scnr = new Scanner(System.in);      

      String pizza;
      double subTotal;
      double totalDue;

      pizza = scnr.next();

      subTotal = 9.99 * pizza;
      totalDue = subTotal * pizza;

    System.out.println(("How many pizzas? ") + pizza); 
    System.out.println(("Sub Total: ") + subTotal);
    System.out.print(("Total Due: ") + totalDue);

}}

Answer 1

您可以使用此方法进行双精度检查（当用户输入数字以外的时候，下面的代码会很有用）-

    double pizza = 0;
    Scanner scnr = new Scanner(System.in);
    System.out.println(" Please enter Pizza :");
    do {
        while (!input.hasNextDouble()){
            System.out.println(" Please enter number :");
            input.next();
        }
        pizza = input.nextDouble();
    }while (pizza  <= 0);