Question

以下代码将为我提供所需的输入数据类型（int，double或string），但是，当我运行代码时，就好像在执行之前需要其他输入一样。我希望我走在正确的道路上。

或

Enter some stuff: 43
3
You have entered an integer: 43

在我输入另一个字符（在这种情况下，是低于43的3个字符）之前，它不会运行。

感谢您的光临。

    public static void main(String[] args) 
    {
        // variables

        Scanner in = new Scanner(System.in);
        String input;

        // Prompt user for stuff

        System.out.print ("Enter some stuff: ");

        // input stuff
        input = in.next();

        //determine and read type echo to use
        if (in.hasNextInt())
        {
        System.out.print ("You have entered an integer: "+ input);
        }
        else if (in.hasNextDouble())
        {
        System.out.print ("You have entered a double: "+ input);
        }
        else if (in.hasNextLine())
        {
        System.out.print ("You have entered a string: "+ input);
        }



    }

Answer 1

我将使用try和catch来找到正确的数据类型。不要使用多个输入，否则会得到错误提示，只需使用in.next()一次，然后按如下所示处理值：

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    String input;

    // Prompt user for stuff

    System.out.print ("Enter some stuff: ");

    // input stuff
    input = in.next();

    //determine and read type echo to use
    try {
        int v = Integer.parseInt(input);
        System.out.print ("You have entered an integer: " + input);
    } catch (NumberFormatException nfe1) {
        try {
            double v = Double.parseDouble(input);
            System.out.print ("You have entered a double: " + input);
        } catch (NumberFormatException nfe2) {
            System.out.print ("You have entered a string: " + input);
        }
    }
}

输出1：

Enter some stuff: 7
You have entered an integer: 7

输出2：

Enter some stuff: 3.0
You have entered a double: 3.0

输出3：

Enter some stuff: sfsdfasd
You have entered a string: sfsdfasd

Answer 2

我认为您做错了。如果您想知道输入的数据类型，为什么要先读取它？您首先要读取并将其存储在input变量中，然后确定下一个输入的输入的类型。因此，该消息也是错误的。我已经更改了您的代码以获得所需的输出

    public static void main(String[] args) {
    // variables

    Scanner in = new Scanner(System.in);
    String input;

    // Prompt user for stuff

    System.out.print ("Enter some stuff: ");

    // input stuff
    // input = in.next();

    //determine and read type echo to use
    if (in.hasNextInt())
    {
    System.out.println ("You have entered an integer: "+ in.nextInt());
    }
    else if (in.hasNextDouble())
    {
    System.out.println ("You have entered a double: "+ in.nextDouble());
    }
    else if (in.hasNextLine())
    {
    System.out.println ("You have entered a string: "+ in.nextLine());
    }

}

停止阅读Java中的标准输入

2 个答案: