Java – How to read a valid Integer number from Console ?

Published on March 2, 2016 by abundantcode

Filed under Java

Last modified March 2, 2016

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Problem Statement

You need to read a valid integer number from the Console in your java program. If the number is invalid , show appropriate message.

Solution

To read a valid integer from a console program , you can use the Scanner class and pass the System.in as the parameter to its constructor. The scanner class exposes a method called nextInt() which can be used to find out if the number is a valid integer or not as shown below.

import java.util.InputMismatchException;
import java.util.Scanner;

public class Main {
    static Scanner helper = new Scanner(System.in);
    public static void main(String[] args) {
       System.out.println("Please enter a valid integer for abundantcode.com ");
       int retValue;
       while(true)
       {
           try
           {
               retValue = helper.nextInt();
               break;
           }
           catch(InputMismatchException ex)
           {
               helper.next();
               System.out.println("This is a invalid number at abundantcode.com");
           }
       }
        System.out.println("You have entered an valid number");

    }
}

Output of the above program is

Please enter a valid integer for abundantcode.com

j

This is a invalid number at abundantcode.com

10

You have entered an valid number

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