How to filter Scanner input errors with try/catch/finally in my programm?

Question

I wrote this little guessing game where you have to guess of cause a random number. I finished this programm but the last thing I would like to to do is: When the user should input a number and its and InputMissmatching error or other errors, the System tells him that he has to input a number taller than 0. But the variable of the Scanner doesn't work after this do-while loop anymore! How to I have to set up the try/catch/finally with a loop to get only integers and not crash when its not an integer or 0?

The problem is that the guessNumber and the numberOfUser variables havent't been initialized now! lines: 37,53 so what do i have to change in the try/catch loop?

package gessinggame;

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

public class GessingGame {

    public static void main(String[] args) {




//<editor-fold desc="Start Variables and Objects">

        Random random = new Random();
        Scanner input = new Scanner(System.in);

        int counter = 0;
        int numberOfUser;
        int guessNumber;
        int x = 1;
        System.out.print("Try to guess my number! What should be the highest number I can go up to?: ");
        do{
        try{
            numberOfUser = input.nextInt();
            guessNumber = random.nextInt(numberOfUser);
            x = 2;
        }catch(Exception e)
        {
            System.out.print("That doesn't work! Please enter an integer higher than 0 :");
            x = 1;
        }
        }while(x == 1);
//</editor-fold>

//<editor-fold desc="do-while loop (higher/lower/equal)">

        System.out.println("Try to guess my number! Its from 0 to " + numberOfUser + " !");
        System.out.println("---------------------------------------------------");

        do{

                int userguess = input.nextInt();

                    if(userguess > numberOfUser)
                    {
                    System.out.println("Oh man, at the beginning you said that the highest number is: " + numberOfUser);
                    }
                    else{       
                            if(userguess < 0)
                            {
                            System.out.println("My number is always taller than 0");
                            } else{  
                                    if(guessNumber < userguess)
                                    {
                                        System.out.println("lower");
                                        counter++;
                                    }
                                    if(guessNumber > userguess) 
                                    {
                                        System.out.println("higher");
                                        counter++;
                                    }
                                    if(userguess == guessNumber) 
                                    {
                                        counter++;
                                        break;
                                    }
                                    }
                        }
            }while(true);

//</editor-fold>

//<editor-fold desc="print final result">

        System.out.println("You guessed my number! My number was: " + guessNumber + "! You needed " + counter + " attempts!");

//</editor-fold>
    }

}

Answer 1

So the problem is that first you need to catch the exception of course. In the try catch you have to clear the buffer then with input.nextLine();

So this should work:

public static void main(String[] args)
{

    // <editor-fold desc="Start Variables and Objects">

    Random random = new Random();
    Scanner input = new Scanner(System.in);

    int counter = 0;
    int numberOfUser = 0;
    int guessNumber = 0;
    int x = 1;
    System.out.print("Try to guess my number! What should be the highest number I can go up to?: ");
    do
    {
        try
        {
            numberOfUser = input.nextInt();
            guessNumber = random.nextInt(numberOfUser);
            x = 2;
        }
        catch (Exception e)
        {
            System.out.print("That doesn't work! Please enter an integer higher than 0 :");
            x = 1;
        }
    } while (x == 1);
    // </editor-fold>

    // <editor-fold desc="do-while loop (higher/lower/equal)">

    System.out.println("Try to guess my number! Its from 0 to " + numberOfUser + " !");
    System.out.println("---------------------------------------------------");

    do
    {

        int userguess = 0;
        try
        {
            userguess = input.nextInt();
        }
        catch (InputMismatchException e)
        {
            System.out.println("Please enter a valid number!");
            input.nextLine();
        }

        if (userguess > numberOfUser)
        {
            System.out.println("Oh man, at the beginning you said that the highest number is: " + numberOfUser);
        }
        else
        {
            if (userguess < 0)
            {
                System.out.println("My number is always taller than 0");
            }
            else
            {
                if (guessNumber < userguess)
                {
                    System.out.println("lower");
                    counter++;
                }
                if (guessNumber > userguess)
                {
                    System.out.println("higher");
                    counter++;
                }
                if (userguess == guessNumber)
                {
                    counter++;
                    break;
                }
            }
        }
    } while (true);

    // </editor-fold>

    // <editor-fold desc="print final result">

    System.out.println(
            "You guessed my number! My number was: " + guessNumber + "! You needed " + counter + " attempts!");

    // </editor-fold>
}

Answer 2

Add input.nextLine() in your try/catch blocks.
call Scanner.nextLine call after each Scanner.nextInt to consume rest of that line including newline.

 package gessinggame;

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

public class GessingGame {

    public static void main(String[] args) {




//<editor-fold desc="Start Variables and Objects">

        Random random = new Random();
        Scanner input = new Scanner(System.in);

        int counter = 0;
        int numberOfUser = 0;
        int guessNumber = 0;
        int x = 1;
        System.out.print("Try to guess my number! What should be the highest number I can go up to?: ");
        do{
        try{
            numberOfUser = input.nextInt();
            guessNumber = random.nextInt(numberOfUser);
            x = 2;
        }catch(Exception e)
        {
            System.out.print("That doesn't work! Please enter an integer higher than 0 :");
            input.nextLine();
            x = 1;
        }
        }while(x == 1);


        System.out.println("Try to guess my number! Its from 0 to " + numberOfUser + " !");
        System.out.println("---------------------------------------------------");

        do{

                int userguess = input.nextInt();

                    if(userguess > numberOfUser)
                    {
                    System.out.println("Oh man, at the beginning you said that the highest number is: " + numberOfUser);
                    }
                    else{       
                            if(userguess < 0)
                            {
                            System.out.println("My number is always taller than 0");
                            } else{  
                                    if(guessNumber < userguess)
                                    {
                                        System.out.println("lower");
                                        counter++;
                                    }
                                    if(guessNumber > userguess) 
                                    {
                                        System.out.println("higher");
                                        counter++;
                                    }
                                    if(userguess == guessNumber) 
                                    {
                                        counter++;
                                        break;
                                    }
                                    }
                        }
            }while(true);
        System.out.println("You guessed my number! My number was: " + guessNumber + "! You needed " + counter + " attempts!");
    }

}