Problem in looping

[Avinash Oak]

Hello All,
I am facing problem with looping statement in my code, this code is for displaying even or odd numbers whatever user will input. Working fine but when I want it to ask for input next number it got failed. Explained below:
1. Console --> Please enter no:
2. User --> 25
3. console --> Even
4. console --> Do you want to continue?
5. User --> Yes
6. //Will repeat same//
7. Console -->Do you want to continue?
8. User --> No
9. //Program Should exit//

I have pasted my code here, please suggest me what to do?

package testing_different_resources;
import java.util.Scanner;
public class Assignment1 {
	
	public static void main(String[]args){
		int num;
		Scanner scnr = new Scanner(System.in);
		do{System.out.println("Please enter no:");
		num = scnr.nextInt();
		if(num%2==0){
			System.out.println("Odd");
			}
		else{
			System.out.println("Even");
			}
		System.out.println("Do you want to continue?");
		if(scnr.next()=="Yes"){
			continue;
			}

		}
	
		while(scnr.next()=="No");
	}
}

[Avinash Oak]

Hi, I think its solved.
Please check my code if there any bug:

package testing_different_resources;
import java.util.Scanner;
public class Assignment1 {
	
	public static void main(String[]args){
		int num;
		String oK = "Yes";
		Scanner scnr = new Scanner(System.in);
		do{
			System.out.println("Please enter no:");
		
			num = scnr.nextInt();
				if(num%2==0){
					System.out.println("Odd");
						}
						else{
							System.out.println("Even");
						}
				System.out.println("Do you want to continue?");
			}
		
		while(scnr.next().equals(oK));
		System.out.println("Exiting...");
		System.exit(0);
		
	}
}

[Stuart A. Burkett]

Have you tried entering a non-numeric value ?

[Avinash Oak]

I tried using try and catch statement with entering "A" as input, but its got fail with some error log:

package testing_different_resources;
import java.util.Scanner;
public class Assignment1 {
	
	public static void main(String[]args){
		int num;
		String oK = "Y";
		Scanner scnr = new Scanner(System.in);
		try{
		do{
			System.out.println("Please enter no:");
		
			num = scnr.nextInt();
				if(num%2==0){
					System.out.println("Odd");
						}
						else{
							System.out.println("Even");
						}
				System.out.println("Do you want to continue? Y / N");
			}while(scnr.next().equals(oK));
		}
		catch(NumberFormatException e){
			System.out.println("Invalid input!");
		}
		System.out.println("Exiting...");
		System.exit(0);
		
	}
}
	

Please suggest what to do, when someone enter Non-numeric values.

Please enter no:
a
Exception in thread "main" java.util.InputMismatchException
	at java.util.Scanner.throwFor(Unknown Source)
	at java.util.Scanner.next(Unknown Source)
	at java.util.Scanner.nextInt(Unknown Source)
	at java.util.Scanner.nextInt(Unknown Source)
	at testing_different_resources.Assignment1.main(Assignment1.java:13)

[Avinash Oak]

Hi, I think its solved, please have a look on my code and check if there still any bug.

package testing_different_resources;
import java.util.InputMismatchException;
import java.util.Scanner;
public class Assignment1 {
	
	public static void main(String[]args){
		int num;
		String oK = "Y";
		Scanner scnr = new Scanner(System.in);
		try{
		do{
			System.out.println("Please enter no:");
		
			num = scnr.nextInt();
				if(num%2==0){
					System.out.println("Odd");
						}
						else{
							System.out.println("Even");
						}
				System.out.println("Do you want to continue? Y / N");
			}while(scnr.next().equals(oK));
		}
		catch(InputMismatchException e){
			System.out.println("Invalid input!");
		}
		System.out.println("Exiting...");
		System.exit(0);
		
	}
}

and below is the output:

Please enter no:
a
Invalid input!
Exiting...

[Junilu Lacar]

Since your "oK" variable is used only once in the program, it's perfectly fine to use the literal string in place. Line 22 can be

        ...
    } while ("YES".equalsIgnoreCase(scnr.next());

Also, you would do well to give a better name than "scnr" -- why are you afraid of vowels? There's no prize for abbreviating variable names. There is a penalty though: "scnr" is much harder to read than "scanner". Besides, you've already declared that variable as a Scanner, why repeat yourself? A name like "userInput" conveys the purpose much better, don't you think?

    // BETTER
        ...
    } while ("YES".equalsIgnoreCase(userInput.next());

    // EVEN BETTER:
        ...
    } while (wantsToContinue(userInput)) // intent revealed

...
// implementation details separated from intent
private boolean wantsToContinue(Scanner consoleInput) {
    return "YES".equalsIgnoreCase(consoleInput.next());
}

[Stuart A. Burkett]

I'd put the try/catch inside the while loop. Let your user try again without having to rerun the program.

[Jesper de Jong]

Have you tried running the program and entering some numbers?

It will print "Odd" for even numbers, and "Even" for odd numbers. Isn't that odd?

[Greg Ferguson]

Jesper de Jong wrote:Have you tried running the program and entering some numbers?

It will print "Odd" for even numbers, and "Even" for odd numbers. Isn't that odd?

I ran the program and saw that too. Fortunately, that's a very easy fix. Other than a few minor things, it works well.

[Henry Wong]

Avinash Oak wrote:Hi, I think its solved, please have a look on my code and check if there still any bug.

and below is the output:

Please enter no:
a
Invalid input!
Exiting...

Are you doing this because that is the desired requirement? Or are you doing it because it is the easiest thing to do?

Wouldn't a better option be ... "invalid input. Please try again." followed by the prompt for another number?

Henry

[Avinash Oak]

Thanks to all !!

Henry, can you please show me how can I do this.

[Avinash Oak]

But I still want my program prompt for "Please enter no:" even user enter a nun-numeric value.

package testing_different_resources;
import java.util.InputMismatchException;
import java.util.Scanner;
public class Assignment1 {

	public static void main(String[]args){
		int num=0;
		Scanner userInput = new Scanner(System.in);

		do{

			try{
				System.out.println("Please enter no:");
				num = userInput.nextInt();


				if(num%2==0)
				{
					System.out.println("Odd");
				}
				else{
					System.out.println("Even");
				}


				System.out.println("Do you want to continue? Yes / No");

			}
			catch(InputMismatchException e){
				System.out.println("Invalid input!");
			}

		}while ("YES".equalsIgnoreCase(userInput.next()));


		System.out.println("Exiting...");

		System.exit(0);

	}
}

[Avinash Oak]

also there is another problem, I cann't use "num" variable without initialization.

[Greg Ferguson]

Avinash Oak wrote:also there is another problem, I cann't use "num" variable without initialization.

It seems to work fine without having to initialize it. I just removed the "=0" part and it still ran. What kind of error did you receive?

[Avinash Oak]

Buenny Fry wrote:

Avinash Oak wrote:also there is another problem, I cann't use "num" variable without initialization.

It seems to work fine without having to initialize it. I just removed the "=0" part and it still ran. What kind of error did you receive?

But can it prompt for "enter number" again after user entered a non-numeric value?

[Winston Gutkowski]

Avinash Oak wrote:But can it prompt for "enter number" again after user entered a non-numeric value?

I think part of your problem is that all your code is in one place. Why not write a method that prompts the user to enter a number, keeps looping until they do, and then returns it when they finally get it right? Maybe something like:

public static int enterNumber(Scanner input, String prompt) {
   ...

(I leave the implementation up to you ).

Then in your main() method, all you have to do is:
num = enterNumber(userInput, "Please enter no:");

Winston