Comparing User Input To Integer

Question

I'm still in the learning part of Java. I've made a kind of guessing game. It looks like this:

import java.util.Scanner;
import java.util.Random;
public class guessing_game {

    static Scanner input = new Scanner(System.in);
    static Random generator = new Random();
    public static void main(String[] args) {
        int number;
        number = generator.nextInt(20);
        System.out.println("Guess the number!");
        game(number);
    }
    public static void game(int number) {
        int inputStorage;
        inputStorage = input.nextInt();
        if (inputStorage == number) {
            System.out.println("You've guessed the right number!");
        }
        else if (inputStorage != number) {
            System.out.println("Wrong number, try again!");
            game(number);
        }
    }
}

Now I have a problem. My little sister and I played this "game". My sister was typing on the numpad. She accidently hit the + button before pressing enter and I got some errors. My question is: How can I let my application print a line which is saying that you can only input numbers and then restarts the game stub again?

Marco Corona · Accepted Answer · 2013-07-09 21:13:20Z

4

One way would be to wrap the input.nextInt() in a try catch statement and catch the exceptions that are thrown by input.nextInt(), InputMismatchException. A good tutorial for try catch statements is here if you aren't sure what I am talking about.

try {
    inputStorage = input.nextInt();
} catch (InputMismatchException e){
    System.out.println("invalid type");
}

Another way you can do this is:

if(input.hasNextInt()){
     inputStorage = input.nextInt();
 }else{
      System.out.println("invalid type");
 }

There is also an error with continuing the game try using a while loop with a break if the number was guessed correctly:

int inputStorage;
boolean notGuessed = true;
while(notGuessed)
{
    if(input.hasNextInt()){
         inputStorage = input.nextInt();
     } else{
         System.out.println("invalid type");
      }
    if (inputStorage == number) {
        System.out.println("You've guessed the right number!");
        notGuessed = false;
    }
    else if (inputStorage != number) {
        System.out.println("Wrong number, try again!");

    }
 }

edited Jul 9, 2013 at 21:13

answered Jul 9, 2013 at 20:53

Marco Corona

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7 Comments

Sander de Lange Over a year ago

I'm a real beginner in Java, is it possible to change the not guessed boolean to guessed and set it to false by default? I'm not on my pc right now so I can't test it...

Marco Corona Over a year ago

Yes this is possible, but you would have to add a logical or to the while condition: while(!guessed).

Sander de Lange Over a year ago

It doesn't work. When I enter a letter the "invalid type" text comes up and doesn't stop printing. It keeps going and going...

Marco Corona Over a year ago

It's not supposed to stop until the number is correctly guessed. If you want a different condition then change the loop structure.

Sander de Lange Over a year ago

I made it print the invalid type text only once but I don't understand why it's working by now. pastebin.com/8m4WsV0T

|

gggttt · Accepted Answer · 2016-05-11 10:01:23Z

1

Well this is quite easy. You can accomplish it in various way.

Try this one

    public static int checkInt(String strNumber) {
    int Number;
    try {           
        Number = Integer.parseInt(strNumber);
    } catch (NumberFormatException ex) {
        Number = -1;
    }
    return Number;
}

Or even simpler:

    public static int checkInt(String strNumber) {

    Number = Integer.parseInt(strNumber, -1);

    return Number;
}

The second one is even simpler because you omit a try catch block, that is rather not correctly used in such case. Read about the functions of Integer class.

edited May 11, 2016 at 10:01

answered Jul 9, 2013 at 21:04

gggttt

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Comments

jh314 · Accepted Answer · 2013-07-09 20:56:47Z

0

You can use a try/catch:

boolean b = true;
while (b) {
    try {
          inputStorage = input.nextInt();
          b= false;
    } catch (InputMismatchException e) {
          System.out.println("Invalid input.  Please enter again!");
    } 
}

answered Jul 9, 2013 at 20:56

jh314

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Comments

user1707035 · Accepted Answer · 2013-07-09 21:01:57Z

0

Since the error you got was an Exceptiion: InputMismatchException.

You can explicitly handle the exception using the Exception handling mechanism in java.

Read this

to know how it actually works.

Above suggested answers are exception handling only.

answered Jul 9, 2013 at 21:01

user1707035

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