CODEWITHSUNDEEP
java
G.M
G.M

Reputation: 663

java IF NOT statement

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

public class Game {
    public static void main(String[] args) {

        System.out.println("Guess a number betwwen 1 and 1000");

        Random rand = new Random(); 
        int secretNumber = rand.nextInt (1000);


        Scanner keyboard = new Scanner(System.in);
        int guess;

        do {
        guess = keyboard.nextInt();

        if (guess == secretNumber)
            System.out.println("You WON!!! Congratulations!");
        else if (guess < secretNumber)
             System.out.println("Nope, to low");
        else if (guess > secretNumber)
            System.out.println("Sorry, to high");


        } while (guess != secretNumber);


    }
}

how can i add to this code a statement, that IF NOT NUMERIC INPUT System.out.println("invalid input, please use type numbers only!")

Upvotes: 2

Views: 32388

Answers (7)

user1581900
user1581900

Reputation: 3720

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

public class Game {
    public static boolean isInteger( String input )  
    {  
       try  
       {  
          Integer.parseInt( input );  
          return true;  
       }  
       catch( Exception e)  
       {  
          return false;  
       }  
    } 

    public static void main(String[] args) {

        System.out.println("Guess a number betwwen 1 and 1000");

        Random rand = new Random(); 
        int secretNumber = rand.nextInt (1000);

        Scanner keyboard = new Scanner(System.in);
        int guess=-1;

        do {
        String g = keyboard.next();
        if(isInteger(g)){
            guess = Integer.parseInt(g);
            if (guess == secretNumber)
                System.out.println("You WON!!! Congratulations!");
            else if (guess < secretNumber)
                System.out.println("Nope, to low");
            else if (guess > secretNumber)
                System.out.println("Sorry, to high");
        }
        else{
            System.out.println("NaN");
        }

        } while (guess != secretNumber);


    }
}

Upvotes: 0

wandi.darko
wandi.darko

Reputation: 610

public class Game {
    public static void main(String[] args) {

    System.out.println("Guess a number betwwen 1 and 1000");

    Random rand = new Random(); 
    int secretNumber = rand.nextInt (1000);


    Scanner keyboard = new Scanner(System.in);
    int guess;

    do {
    if (!keyboard.hasNextInt()) {
        System.out.println("invalid input, please use type numbers only!");
        return;
    }
    guess = keyboard.nextInt();

    if (guess == secretNumber)
        System.out.println("You WON!!! Congratulations!");
    else if (guess < secretNumber)
         System.out.println("Nope, to low");
    else if (guess > secretNumber)
        System.out.println("Sorry, to high");


    } while (guess != secretNumber);


    }
}

Upvotes: 0

Sanchit
Sanchit

Reputation: 2260

While using a scanner you will never figure out if it is an integer that has been entered or not. It will just wait until the "nextInt" is entered. What you can do is use the

Integer.parseInt() method. It will throw a NumberFormatException if the input string is not an integer.

Make guess a string and use. guess = keyboard.next();

Then use Integer.parseInt(guess) in a try-catch to solve your problem.

Upvotes: 0

Scott
Scott

Reputation: 12376

You can add a try catch block inside your loop.

  do {
  try{
    guess = keyboard.nextInt();

    if (guess == secretNumber)
        System.out.println("You WON!!! Congratulations!");
    else if (guess < secretNumber)
         System.out.println("Nope, to low");
    else if (guess > secretNumber)
        System.out.println("Sorry, to high");
    }
catch(InputMismatchException e){
System.out.prinln("Not a number");
}


    } while (guess != secretNumber);

Upvotes: 0

Corey Adler
Corey Adler

Reputation: 16149

I think you want the following wrapped around guess = keyboard.nextInt():

 try  
 {  
     guess = keyboard.nextInt()
     Integer.parseInt(guess);  

     <your if statements>

  } catch(Exception ex)  
  {  
    System.out.println("Your comment");
  }

Upvotes: 1

gtgaxiola
gtgaxiola

Reputation: 9331

Scanner.nextInt() throws InputMismatchException if the next token does not match the Integer regular expression, or is out of range

So you should wrap your code around a try-catch with this in mind

Upvotes: 3

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726809

You should use Scanner's hasNextInt() method to determine if the input is numeric before calling nextInt:

do {
    while (!keyboard.hasNextInt()) {
        System.out.println("Please enter only numbers.");
        keyboard.next(); // Skip the wrong token
    }
    // Now that the input is valid, read the value:
    guess = keyboard.nextInt();
    // Put the rest of your logic here
    ...
} while (guess != secretNumber);

Upvotes: 6

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