java - 如何管理用户输入字母而不是数字？

Question

我正在尝试编写一个自动售货机程序，除了告诉它如何处理用户输入字母而不是数字之外，它还做得很好。这是我试图弄清楚的代码块:

System.out.print("Please enter how much money you have to spend (enter -1 to shut down): ");
        double custMoney = scanner.nextDouble();
        if (custMoney <= 0) {
            System.out.println("Thank you for your business!");
            System.exit(0);
        }

如果用户输入字母而不是数字，它会给我

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.nextDouble(Unknown Source)
at VendingMachine1.main(VendingMachine1.java:28)

如何解决此问题，以便在他们输入字母时提示他们输入有效的数字？

Answer 1

正如@Max所说，您应该将输入读取为字符串，并在它不是数字时提醒用户，我添加了 while(!numberOk) ，这样如果用户输入字母而不是数字(或无效数字)，它会继续询问;)

希望这对您有帮助

   String custMoney = scanner.next();
    double custMoneyValue;
    boolean numberOk=false;
    while(!numberOk)
    try {
        custMoneyValue = Double.parseDouble(custMoney);
        if (custMoneyValue <= 0) {
            System.out.println("Thank you for your business!");
            numberOk=true;
            System.exit(0); // would make the while loop condition useless...

        }
    }catch (NumberFormatException e) {
            System.out.println("Please insert a number...");
            custMoney = scanner.next();
    }