How do I check if user input is an integer or not.

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Hi this is Java question,
From this code, I am trying to accept a user input and store it in an integer variable. Then, I am trying to validate the variable to check if the input is an integer or not. If the input is an integer, you print "The input is an integer".

However, if the user input is not of integer type, then we prompt the user to enter the number again until the user inputs an integer. I have tried the following code below using try and catch:
Please help.

What I have tried:

import java.util.*;

public class studentExpensesUOWD {
	//Used to define a new object that would contain all input functions.
	static Scanner console = new Scanner (System.in);
	
	public static void main(String[] args) {
		
		int number;
		boolean done = false;
		do
		{
			try
			{
				System.out.print("Enter a number: ");
				number = console.nextInt();
				done = true;
		}
			catch (InputMismatchException e)
			{
				System.out.println("Invalid integer input");
			}
		} while (done == false);
			
			
		System.out.println("Integer Value Accepted");
		System.exit(0);
	}

}

Posted 30-Oct-17 17:20pm

Member 13494728

Updated 14-Jun-20 23:12pm

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3 solutions

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Peter Leow · Answer 1 · 2017-10-30T17:32:00

Solution 1

Use hasNextInt[^] of the Scanner class.
An example Java.util.Scanner.hasNextInt() Method Example[^]

Posted 30-Oct-17 17:32pm

Peter Leow

Comments

Member 13494728 31-Oct-17 0:27am

I do not know how to use that method.
Could you please provide a small example?

CPallini 31-Oct-17 6:05am

5.

Peter Leow 1-Nov-17 10:38am

Thank you, CPallini.

wseng · Answer 2 · 2017-10-30T23:52:00

Solution 2

You need to add

console.next();

after

System.out.println("Invalid integer input");

Refer on java - Scanner is skipping nextLine() after using next(), nextInt() or other nextFoo()? - Stack Overflow[^]

Posted 30-Oct-17 23:52pm

wseng

Member 14863353 · Answer 3 · 2020-06-14T23:12:00

System.out.print("Enter a number: ");
do {
  try {
	if ( number.hasNextInt() ) {
            number = console.nextInt();
	    done = true;
        }
       } catch (InputMismatchException e) {
          System.out.println("Invalid integer input");
          System.out.print("Enter a number: ");
      } 
   } while (done == false);

System.out.println("Integer Value Accepted");