Question

如何验证此代码以便用户只能输入整数？

import java.util.Scanner;

public class TrainTester
{

    public static void main(String[] args)
    {
        boolean retry = true;

    while (retry) 
    {
        RailroadCar RRCar = new RailroadCar();
        PassengerCarriage PCar = new PassengerCarriage();
        GoodsCar GCar = new GoodsCar();
        RefrigeratedUnit RUnit = new RefrigeratedUnit();


        Scanner sc =  new Scanner(System.in);
        System.out.println("===================================");
        System.out.println("Please enter number between 1 and 4");
        int i = sc.nextInt();

            if (i == 1)
            {
                RRCar.calculateTotalWeight();
                RRCar.displayDetails();
            }
            else if   (i == 2)
            {
                System.out.println("Enter the amount of passengers in the carriage");
                int temp = sc.nextInt();
                PCar.setNOP(temp);

                PCar.calculateTotalWeight();
                PCar.displayDetails();
            }   
            else if (i == 3)
            {
                System.out.println("Enter the weight of the goods");
                int temp1 = SC.nextInt();
                GC.setGW(temp1);

                GC.calculateTotalWeight();
                GC.displayDetails();
            }
            else if (i == 4)
            {
                System.out.println("Enter the weight of the goods");
                int temp2 = sc.nextInt();
                RUnit.setGWeight(temp2);

                System.out.println("Enter the weight of the coolant");
                double temp3 = sc.nextInt();
                RUnit.setCWeight(temp3);

                RUnit.calculateTotalWeight();
                RUnit.displayDetails();
            }
            else 
            {
                System.out.println("=========================================================================================")
                System.out.println("Please enter a number from the list below, each number represents the different carriages");
                System.out.println(" ");
                System.out.println("1. RailRoad Carriage");
                System.out.println("2. Passenger Carriage");
                System.out.println("3. Goods Carriage");
                System.out.println("4. Refrigerated Unit");
                System.out.println("=========================================================================================")
            }
        }
    }           
}
}

Answer 1

你可以做这件事：

 int yourNumber;
 final String i = sc.nextLine();
 try {
     yourNumber = Integer.valueOf(i);
 } catch (NumberFormatException ex) {
     //not a number
 }

Answer 2

您可以像这样过滤输入值。

int choice  = sc.nextInt();
int i;
try{
  i= Integer.parseInt(choice);
}catch(Exception e){
  System.out.println("Not an integer");
}

Answer 3

以下是仅验证正数的示例。

Scanner sc = new Scanner(System.in);
int number;
do {
    System.out.println("Please enter a positive number!");
    while (!sc.hasNextInt()) {
        System.out.println("That's not a number!");
        sc.next(); // this is important!
    }
    number = sc.nextInt();
} while (number <= 0);
System.out.println("Thank you! Got " + number);

或者这是最简单的方法

try {
     int i = Integer.parseInt(myString);
        if (i < 0) {
       // Error, negative input
        }
    } catch (NumberFormatException e) {
       // Error, not a number.
}

Answer 4

int choice  = sc.nextInt();
  int i;
   try{
        i= Integer.parseInt(choice);
       }catch(Exception e){
     System.out.println("Not an integer");
   }

如果数字是整数异常，则不会发生其他明智的异常

验证所以输入在java中只是整数

4 个答案: