java - 停止读取 Java 中的标准输入

Question

下面的代码将为我提供我想要的输入数据类型(int、double 或 string)，但是，当我运行代码时，它就像在执行之前需要另一个输入一样。我希望我走在正确的道路上。

或

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

直到我输入另一个字符(在本例中是 43 以下的 3)之前它不会运行。

感谢您的浏览。

    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

我会使用 try 和 catch 来找到正确的数据类型。不要使用多个输入，否则您将收到错误，只需使用 in.next() 一次，然后按如下方式处理值:

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