Java try/catch - 找到 "return isn' t“或初始化 "variable isn' t”？

Question

我已经盯着它看了好几个小时了，想不出解决办法；我通常使用正则表达式处理这种类型的验证，但我正在尝试使用内置解决方案进行更改(显然，我不经常这样做):

private static double promptUserDecimal(){
    Scanner scan = new Scanner(System.in);
    System.out.println("Enter a decimal");
    try{
        double input2 = Double.parseDouble(scan.nextLine());
        return input2;
    } catch(NumberFormatException e){
        System.out.println("Sorry, you provided an invalid option, please try again.");
    }
}

此错误是编译器未找到“return”，因此出现编译错误。如果我将“return”放在 try/catch 之外，我需要声明/初始化“input2”，这违背了操作的目的。感谢任何帮助...

Answer 1

如果你想让用户“请再试一次”，听起来你需要一个循环:

private static double promptUserDecimal(){
    final Scanner scan = new Scanner(System.in);

    // Ask for input until we get something valid
    while (true) {  // Terminated by return within
        System.out.println("Enter a decimal");
        try {
            return Double.parseDouble(scan.nextLine());
        } catch(NumberFormatException e){
            System.out.println("Sorry, you provided an invalid option, please try again.");
            // No return, so the loop will run again
        }
    }
}