CODEWITHSUNDEEP
javawhile-loopdigits
mjamev10
mjamev10

Reputation: 13

Java, even number of even digits, odd number of odd digits

This program is essentially a game where the user must enter numbers to see which numbers are good: numbers with an even number of even digits, and an odd number of odd digits.

So first of all, the program ends when I enter a one digit number, which is not intentional. I assume that has something to do with the while being while (n > 0). There also is likely an issue with the if (numEven % 2 == 0......) because the print results seem almost random, with a number being good and the same number not being good sometimes.

Honestly, I am lost at this point. Thank you so much in advance for any help.

UPDATE: This code is working how I want it to, I just wanted to thank everybody who helped out! It's my first semester of computer science class, so I'm still rather new at this...excuse my mistakes that were likely pretty stupid :)

package quackygame;
import java.util.Scanner;
public class QuackyGame 
{
    public static void main(String[] args) 
   {
       System.out.println("Welcome to the Number Game!"
                + " Try to figure out the pattern "
                + "in the numbers that Wallace likes!");

        Scanner scan = new Scanner (System.in);
        int n;
        int numEven = 0;
        int numOdd = 0;
        boolean isEven;

        do
        {
           System.out.print("Enter a number > 0: ");
           n = scan.nextInt();
           while (n > 0)
           {
               if (n % 2 == 0)
                 {
                   //n is even
                   isEven = true;
                   numEven++;
                 }
                else
                 {
                   //n is odd
                   isEven = false;
                   numOdd++;
                 }
               n /= 10;
           }
           //if numEven is even and numOdd is odd
           if (numEven % 2 == 0 && numOdd % 2 == 1)
               System.out.println("Wallace liked your number!");
           else
           {
               System.out.println("Wallace didn't like your number.");
           }
           numEven = 0;
           numOdd = 0;

        }

        while (n >= 0); 
    }

}

Upvotes: 1

Views: 3546

Answers (2)

Michael Fourre
Michael Fourre

Reputation: 3015

There are a few core issues in the code based on the desired results that you described. The most glaring issue I see is that you intend for the game to essentially "start from scratch" at the beginning of each round, but you never actually reset the numEven and numOdd variables. This is the source of your print results seeming random. For example, if you started a game and input the number:

34567

The game would process the number and say that it is a favorable number because it is odd, has an odd number of odd digits (3), and has an even number of even digits (2). However, upon playing the game again, it would execute the same code without setting the variables back to 0, which means that upon entering:

34567

The game would process this number as a bad number because the accumulated value of odd digits would be 6 instead of 3 (since 3 the first time + 3 the second time results in 6), and 6 is even. So what we want to do is this:

...

int n;

do
{
    int numEven = 0;
    int numOdd = 0;

    System.out.print("Enter a number: ");
    n = scan.nextInt();

...

By placing the numEven and numOdd declarations inside of the "do" block, they are local variables which only exist for the duration of the do block. We could also do something as simple as this:

...

    else
    {
        System.out.println("Wallace didn't like your number.");
    }
    numEven = 0;
    numOdd = 0;
}
while (n > 0);

...

Just resetting the values will help us to keep track of the actual intended values of numOdd and numEven more consistently.

With regard to the program closing when you input a single digit number, I'm not sure. That doesn't make sense because since it is a do-while loop it should at least execute once, and issue one of the print statements. I'm loading this code into my IDE right now to give it a run through. I'll update my answer if I find something.

-EDIT-: Upon reading your question again, it seems that you may not be suggesting that the program closes before actually completing any of its functions, but simply that it closes at all. The reason for the closing of the program is that you are performing an integer division arithmetic function where you probably want to be using a different type of number. Let me explain:

In normal human counting, we have our natural set of numbers which have no decimal points. They usually start like this:

1, 2, 3, 4, 5 ...

Then we have a separate set of numbers for math where we operate with more precision:

0.5, 1.4232, 3.142 ...

When we are talking about numbers with normal human language, we assume that dividing 1 by 2 results in 0.5. However, computers do not implicitly know this. In order for a computer to reach the conclusion "0.5" from the division of 1 by 2, you need to explicitly tell it that it should use a certain type of number to produce that output.

The "normal" numbers I referenced earlier are most loosely related to the integer in programming. It's basically a number without a decimal point. What that means is that whenever you divide two integers together, you always get another integer as the result. So if you were to divide 1 by 2, the computer would not interpret the result as 0.5 because that number has a decimal. Instead, it would round it down to the nearest integer, which in this case is 0.

So for a more specific example referencing the actual question at hand, let's say we input the number 5 into our program. It goes through all of the calculations for odds and evens, but eventually gets to this line:

n /= 10

This is where things get funky. We are dividing two integers, but their result does not come out as a perfect integer. In this case, the result of 5 / 10 is again 0.5. But for the computer, since we are dividing two integers, the result 0.5 just won't do, so after rounding down to the nearest integer we get 0. At this point, there is one fatal mistake:

(while n > 0);

When we perform this check, we get false and the while loop ends. Why? Because after performing n /= 10, n becomes 0. And 0 is not greater than 0.

How can we fix this? The best thing to do is probably just use a floating point number to perform the calculations. In Java, this is pretty easy. All we really have to do is:

n /= 10.0

When Java sees that we are dividing by 10.0, which is not an integer, it automatically converts "n" to a floating point number to divide by 10.0. In this case then, if n is 5, our result in dividing 5 by 10.0 will be 0.5. Then, when we run:

(while n > 0);

This becomes true! And the loop does not break.

I am going to put all of these changes into my IDE just to confirm that everything is working as intended for me. I would suggest you give it a try too to see if it fixes your problems.

Hope this helps.

Upvotes: 1

Sekula1991
Sekula1991

Reputation: 288

You are increasing numEven or numOdd count each time you input a number, and then you use if (numEven % 2 == 0 && numOdd % 2 == 1) , it is random because if you put number 33 for the first time => numOdd = 1; => true => "Wallace likes" , but next time you put 33 for the second time => numOdd = 2; => false => "Wallace doesnt like".

Edit* Maybe you wanted something like this?

public static void main(String[] args) 
{
       System.out.println("Welcome to the Number Game!"
                + " Try to figure out the pattern "
                + "in the numbers that Wallace likes!");

        Scanner scan = new Scanner (System.in);
        int n;
        boolean isEven;

        do
        {
           System.out.print("Enter a number: ");
           n = scan.nextInt();

           //if 0, you leave the loop
           if(n==0) {
               System.out.println("You pressed 0, have a nice day");
               break;
           }
           if (n % 2 == 0)
           {
               //it is even
               isEven = true;
           }

           else
           {
               //it is not even
               isEven = false;
           }


           //if even then he likes it, otherwise he does not
           if (isEven)
               System.out.println("Wallace liked your number!");
           else
           {
               System.out.println("Wallace didn't like your number.");
           }

        }
        //put any contition here, lets say if you press 0 , you leave the loop
        while (n != 0); 
    }

Upvotes: 0

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