Println打印多次，而不是每次循环都增加

Question

I'm trying to make this code print out the number of games played ( gameNum ). Instead, it always sets gameNum to 2 , and prints out the last println the number of times that the game was played. I feel like I made a dumb mistake here, but I am having trouble finding it. Could you please give me a hint instead of the answer? I'd like to figure this out on my own. If not, then feel free to go ahead and write the answer.

Thanks!

import java.util.*;

public class Testing_gameNum {
    public static final int amt = 1;
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        guessCounter(console);
    }

    public static int game(Scanner console) {
        Random rand = new Random();
        int guess = 0;
        int guessNum = 0;
        System.out.printf("I'm thinking of a number...", amt);
        System.out.println();
        int num = 1;

        do {
            System.out.println("Your guess? ");
            guess = console.nextInt();
            guessNum += guessNum;
        } while (guess != num);

        return guessNum;
    }

    public static void guessCounter(Scanner console) {
        int gameNum = 1;
        int guessNum = game(console);
        if (guessNum == 1){
            System.out.printf("You won in %d guesses!", guessNum);
            System.out.println();
        }
        gameNum = gameNum + 1;
        System.out.println("Do you want to play again?");
        String play = console.next();
        if (play.equals("y")) {
            guessCounter(console);
        }
        System.out.println("Number of games: " + gameNum);
    }
}

Answer 1

• Check for every place gameNum is used. I found it ie in the method guessCounter(Scanner console) - and only there.
• So every time you call this method, the value of gameNum is initialized to 1. After the game is won, you increment it by 1 and later on print it, hence the 2 in the output.
• Move int gameNum = 1; out of the method guessCounter(Scanner console) . This should help.

Aside of this please review also the code block

if (play.equals("y")) {
  guessCounter(console);
}

Imagine a player goes on and on, always selecting "y". With every game round, you create another level of recursion. This "do you want to play again" could be implemented by a do-while loop, this will avoid the recursion.

Answer 2

Try something like this:

public class Testing_gameNum
{
   public static final int amt = 1;
   public static void main(String[] args)
   {
      Scanner console = new Scanner(System.in);
      guessCounter(console);
   }

   public static int game(Scanner console)
   {
      Random rand = new Random();
      int guess = 0;
      int guessNum = 0;
      System.out.printf("I'm thinking of a number...", amt);
      System.out.println();
      int num = 1;
      do
      {
         System.out.println("Your guess? ");
         guess = console.nextInt();
         guessNum += amt;
      }
      while (guess != num);
      return guessNum;
   }
   public static void guessCounter(Scanner console)
   {
      int gameNum = 1;
      do
      {
         int guessNum = game(console);
         if (guessNum == 1)
         {
            System.out.printf("You won in %d guesses!", guessNum);
            System.out.println();
         }
         gameNum = gameNum + 1;
         System.out.println("Do you want to play again?");
         String play = console.next();
      }
      while (play.equals("y"))
      System.out.println("Number of games: " + gameNum);
   }
}

Answer 3

You've defined guessCounter to be a recursive method, but that's probably not what you want for several reasons. First, each time you call guessCounter , you're creating a new gameNum and setting it to 1 . You play the game and increment it to 2 , but then recurse and never touch that variable again, which is the cause of your bug. Additionally, (although this is unlikely to happen in usual play), you could overflow your stack if you play the game enough times. Each time you play the game, the computer needs to remember the point in code that it needs to return to when it completes that call of guessCounter . Eventually you will run out of memory to store those pointers. Recursion is good for certain problems, but it's better to use loops most of the time.

How about using a loop rather than recursion.

Answer 4

I solved my question! Here's the code (explanation below):

public class Testing_gameNum {
    public static final int amt = 1;
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        guessCounter(console);
    }

    public static int game(Scanner console) {
        Random rand = new Random();
        int guess = 0;
        int guessNum = 0;
        System.out.printf("I'm thinking of a number...", amt);
        System.out.println();
        int num = 1;

        do {
            System.out.println("Your guess? ");
            guess = console.nextInt();
            guessNum ++;
        } while (guess != num);

        return guessNum;
    }

    public static void guessCounter(Scanner console) {
        int gameNum = 0;
        String play = "y";
            do {
                int guessNum = game(console);
                gameNum += 1;
                if (guessNum == 1) {
                    System.out.printf("You won in %d guesses!", guessNum);
                    System.out.println();
                }
                System.out.println("Do you want to play again?");
                play = console.next();
            } while (play.equals("y"));
        System.out.println("Number of games: " + gameNum);
    }
}

MY PROBLEMS: gameNum was resetting each time I called guessCounter . I needed a do/while loop; that way, I could initialize gameNum inside the method, and then loop only the section of the method that needed to be repeated. The repetitive println was linked with that same issue: it was reprinted each time I called guessCounter , as opposed to just the part of the code I wanted repeated.

Thanks for your help, everyone!