从Scanner输入Java接收浮动 [英] Receiving float from Scanner input Java

问题描述

我需要一个方法来检查用户的输入是否是一个浮点数，如果是字符串或整型，它应该抛出一个异常。

我在这个方法之外声明了扫描器：

pre code> Scanner sc =新的扫描仪（System.in）;

而方法定义是：

<$ p $（$）$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $'
}
else {
float input = sc.nextFloat（）;
if（input％1 == 0）{
throw new MyException（Wrong type）;
}
else返回true;




$ b $ p
$ b

问题是无论如何抛出异常用户输入，所以我的问题是：我究竟做错了什么？

我知道在Java中，像1.2这样的输入被解释为double，但是如何获取从控制台的浮动呢？或者我误解了方法hasNextFloat（）或整个扫描仪的工作？

到目前为止我还没有找到有用的东西

nextFloat（），所以您必须确保输入一个浮点数，否则清除扫描程序与 next（）

  public static void main（String [] args）抛出Exception {
 while（true）{
 System.out.print（Enter a float：）; 
尝试{
 float myFloat = input.nextFloat（）; 
 if（myFloat％1 == 0）{
 throw new Exception（Wrong type）; 
} 
 System.out.println（myFloat）; 
 catch（InputMismatchException ime）{
 System.out.println（ime.toString（））; 
 input.next（）; //从所有数据
 
 
 
 code 
 
 
 $ b 
结果：
 
   
 
 
 UPDATE 
 
 
 
您仍然必须处理InputMismatchException，只是在catch块中抛出自己的异常。 （$ {
 
 
> public static void main（String [] args）{
 Scanner input = new Scanner（System.in）; 
 
 // while（true）仅用于测试
 while（true）{
 try {
 System.out.print（Enter a float：）; 
 System.out.println（CheckFloat（input））; 
} catch（MyException me）{
 System.out.println（me.toString（））; 
 
 
 
 $ b private static float CheckFloat（Scanner sc）throws MyException {
 try {
 float input = sc.nextFloat （）; 
 if（input％1 == 0）{
 throw new MyException（Wrong type）; 
} else {
 return input; 
 
 catch（InputMismatchException ime）{
 sc.next（）; //刷新扫描器
 
 //重新创建自己的异常
抛出new MyException（Wrong type）; 
 
 
 
私有静态类MyException扩展异常{
 //您异常详细信息
 public MyException（String message）{
 super （信息）; 
 
 
 
 
 $结果：
 
 
  
 
I need a method that should check whether user's input is a float, and if it is string or int it should throw an exception. 

I declare the Scanner outside of the method:
    Scanner sc = new Scanner(System.in);
And the method definition is:
private boolean CheckFloat(Scanner sc) throws MyException {
    if(!sc.hasNextFloat()){
        throw new MyException("Wrong type");
    }
    else {
        float input = sc.nextFloat();
        if(input%1==0) {
            throw new MyException("Wrong type");
        }
        else return true;
    }
}
The problem is that the exception is thrown no matter what the user types in, so my question is: what exactly do I do wrong?

I know that in Java an input like 1.2 is interpreted as double, but how to take a float from the console then? Or do I misunderstand working of the method hasNextFloat() or the whole Scanner?

I haven't found anything helpful so far
解决方案
Since you're using nextFloat() you must be sure that you enter a floating number, otherwise clear the scanner with next()
public static void main(String[] args) throws Exception {
    while (true) {
        System.out.print("Enter a float: ");
        try {
            float myFloat = input.nextFloat();
            if (myFloat % 1 == 0) {
                throw new Exception("Wrong type");
            }
            System.out.println(myFloat);
        } catch (InputMismatchException ime) {
            System.out.println(ime.toString());
            input.next(); // Flush the buffer from all data
        }
    }
}
Results:



UPDATE

You still have to handle the InputMismatchException, just throw your own exception in the catch block.
public static void main(String[] args) {
    Scanner input = new Scanner(System.in);

    // while (true) just for testing
    while (true) {
        try {
            System.out.print("Enter a float: ");
            System.out.println(CheckFloat(input));
        } catch (MyException me) {
            System.out.println(me.toString());
        }
    }
}

private static float CheckFloat(Scanner sc) throws MyException {
    try {
        float input = sc.nextFloat();
        if (input % 1 == 0) {
            throw new MyException("Wrong type");
        } else {
            return input;
        }
    } catch (InputMismatchException ime) {
        sc.next(); // Flush the scanner

        // Rethrow your own exception
        throw new MyException("Wrong type");
    }
}

private static class MyException extends Exception {
    // You exception details
    public MyException(String message) {
        super(message);
    }
}
Results:



                        
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