Output copied twice in Nim game in Java

Question

Im learning java with "programmingbydoing" and i have a problem with Nim game, everything works fine apart from one thing, which is that both:

"System.out.print(n1 + ", choose a pile: ");" 

and

"System.out.print(n2 + ", choose a pile: ");"

is out printed twice after the first time.

Here is code:

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        System.out.print("Player one, enter your name: ");
        String n1 = input.nextLine();

        System.out.print("Player two, enter your name: ");
        String n2 = input.nextLine();

        int a = 3;
        int b = 4;
        int c = 5;
        int count = 1;

        System.out.println("A: "+a+" B: "+b+" C: "+c);

        nim_loop:while(a > 0 || b > 0 || c > 0) {

            while(count % 2 != 0 ) {
                System.out.print(n1+", choose a pile: ");
                String first = input.nextLine();

                if (first.contains("a") || first.contains("A")) {
                    System.out.print("How many to remove from pile " + first + "? ");
                    int second = input.nextInt();
                    count = count + 1;

                    a = a - second;

                    System.out.println("A: " + a + " B: " + b + " C: " + c);

                    if(a <= 0 && b <= 0 && c <= 0){
                        break nim_loop;
                    }

                }
                else if (first.contains("b") || first.contains("B")) {
                    System.out.print("How many to remove from pile " + first + "? ");
                    int second = input.nextInt();
                    count = count + 1;

                    b = b - second;

                    System.out.println("A: " + a + " B: " + b + " C: " + c);

                    if(a <= 0 && b <= 0 && c <= 0){
                        break nim_loop;
                    }
                }
                else if (first.contains("c") || first.contains("C")) {
                    System.out.print("How many to remove from pile " + first + "? ");
                    int second = input.nextInt();
                    count = count + 1;

                    c = c - second;

                    System.out.println("A: " + a + " B: " + b + " C: " + c);

                    if(a <= 0 && b <= 0 && c <= 0){
                        break nim_loop;
                    }

                }
            }

            while(count % 2 == 0) {
                System.out.print(n2 + ", choose a pile: ");

                String third = input.nextLine();

                if (third.contains("a") || third.contains("A")) {
                    System.out.print("How many to remove from pile " + third + "? ");
                    int fourth = input.nextInt();
                    count = count + 1;

                    a = a - fourth;

                    System.out.println("A: " + a + " B: " + b + " C: " + c);
                } else if (third.contains("b") || third.contains("B")) {
                    System.out.print("How many to remove from pile " + third + "? ");
                    int fourth = input.nextInt();
                    count = count + 1;

                    b = b - fourth;

                    System.out.println("A: " + a + " B: " + b + " C: " + c);
                } else if (third.contains("c") || third.contains("C")) {
                    System.out.print("How many to remove from pile " + third + "? ");
                    int fourth = input.nextInt();
                    count = count + 1;

                    c = c - fourth;

                    System.out.println("A: " + a + " B: " + b + " C: " + c);
                }
            }

        }

        if (count % 2 != 0) {

            System.out.println("Game ended, Player " + n1 + " is a winner.");
        } else if (count % 2 == 0){
            System.out.println("Game ended, Player " + n2 + " is a winner.");
        } 
    }
}

And here are the pictures of what happens when i run it:

Answer 1

When the first if condition in first inner loop is true and when you get the user input by using nextInt() it only reads the int value and does not consume the last new line character i,e \n. So the subsequent call to nextLine() will be skipped i,e the nextLine() call in second inner while loop will be skipped without any value but System.out.print(n2 + ", choose a pile: "); will be printed as it is before nextLine() call and control goes back to outer while loop.

Now the count value is 2 so first inner while condition will be false and control goes to second inner while loop. And again it prints b, choose a pile:. Hope this clears your question

Workaround is fire a blank nextLine() call after every nextInt() or use nextLine() inside if condition and parse the user input using Integer.parseInt(String) method.

Example code :

if (first.contains("a") || first.contains("A")) {
  System.out.print("How many to remove from pile " + first + "? ");
  int second = input.nextInt();
  input.nextLine(); // firing an blank nextLine call
  count = count + 1;
  a = a - second;
  System.out.println("A: " + a + " B: " + b + " C: " + c);

  if(a <= 0 && b <= 0 && c <= 0){
     break nim_loop;
  }

For more information - Scanner is skipping nextLine() after using next(), nextInt() or other nextFoo() methods