Question

嗨在我的程序中，如果我在字段中输入数字，它应显示为有效值，如果我输入字母或特殊字符，它应显示为无效值，但是当我运行以下代码时，如果我输入单词则显示错误作为输入，如果输入数字，则表示格式正确

  package quantity;


import java.util.Scanner;
public class Quantity {


public static void main(String[] args) {

    Scanner input =new Scanner(System.in);
    System.out.println("enter input");
    double qty = input.nextDouble();
    System.out.println(" input ="+qty);
    if(!("[_a-z_A-Z_)+").equals("qty")||
            !("[_!_~_@_#_$]").equals("qty"))
    {
        System.out.println("correct format");
    }
    // TODO code application logic here

    else
    {
        System.out.println("wrong input");
    }
}

}

显示以下错误

  Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Scanner.java:864)
   at java.util.Scanner.next(Scanner.java:1485)
    at java.util.Scanner.nextDouble(Scanner.java:2413)
    at quantity.Quantity.main(Quantity.java:19)

Answer 1

或... 你可以像这样自己捕捉异常：

import java.util.Scanner;

public class Answer {

    private static final Scanner IN = new Scanner(System.in);

    public static void main(String[] args) {

        double qty;
        while(true){ //infinite loop
            try{
                System.out.println("Please enter the qty:");
                qty = IN.nextDouble();
                System.out.println("You entered " + qty);
                //do something with qty
            }catch(Exception e){
                System.out.println("Please input the number in double format");
                IN.next(); //consume the wrong input
            }
        }

    }

}

字母扫描程序错误

1 个答案: