User input to repeat program in Java

Question

I am writing a simple guessing game program where the user will input a number to try and guess a randomly generated number.

If they get the number right I want to give them the option to play again.

Here is my code:

public class GuessingGame {
    private Random num = new Random();       
    private int answer = num.nextInt(10);   
    private int guess;  
    private String playAgain;  

    public void inputGuess(){
        System.out.println("Enter a number between 1 and 10 as your first guess: ");
        Scanner input = new Scanner(System.in);
        guess = input.nextInt(); 
        do{
        if (guess < 1 || guess > 10){
            System.out.println("That is not a valid entry. Please try again: ");
            guess = input.nextInt();
        }else if (guess > answer){
            System.out.println("Too high, Try Again: ");
            guess = input.nextInt();
        }else if (guess < answer){
            System.out.println("Too low, Try Again: ");
            guess = input.nextInt();
        }

        }while (guess != answer);

        System.out.println("Congratulations, You guessed the number!");
        System.out.println("Would you like to play again? Enter Y to play or any other key to quit: ");
        playAgain = input.nextLine();
        if(playAgain == "Y" || playAgain == "y"){
            System.out.println("Enter a number between 1 and 10 as your first guess: ");
            guess = input.nextInt(); 
        }

    }
}

The game plays through but when the user is prompted to play again nothing happens?

Any suggestions?

Don't compare strings with ==. Instead do if (playAgain.equals("Y")). — Arvy
– Arvy, Commented Oct 14, 2014 at 18:23
When the user enters "Y", you need to start the loop all over again. — Susie
– Susie, Commented Oct 14, 2014 at 18:25
Exactly what @Arvy said. Also, Random.nextInt(10) gives you a value between 0 - 9 so you should either say Random.nextInt(11) OR change your first if statement to if(guess < 0 || guess > 9) — nem035
– nem035, Commented Oct 14, 2014 at 18:25
There are plenty of things wrong: you are comparing strings with ==, you are generating a number from 0-9 (try Random.nextInt(11)), and you forget to catch the return character at the end of scan.nextInt() [which is why it is not prompting you to restart] [try putting: input.nextLine(); in your do loop after the if statements...], also you are looping it incorrectly. — user2494817
– user2494817, Commented Oct 14, 2014 at 18:28

user2494817 · Accepted Answer · 2014-10-14 18:44:27Z

2

Here is the completed code, fully working and tested... without using recursion.. and everything fixed.

    public static void main(String[] args)
    {
    String playAgain = "";
    Scanner scan = new Scanner(System.in);

    do
    {
        ClassName.inputGuess();
        System.out.println("Would you like to play again? Enter Y to play or any other key to quit: ");
        playAgain = scan.nextLine();
    }
    while(playAgain.equalsIgnoreCase("Y"));
    System.out.println("Thanks for playing!");
}

public void inputGuess()
{
    Random num = new Random();
    int answer = num.nextInt(10)+1;
    Scanner input = new Scanner(System.in);
    int guess;

    System.out.println("Enter a number between 1 and 10 as your first guess: ");
    guess = input.nextInt(); 

    do
    {
        if (guess < 1 || guess > 10)
        {
            System.out.println("That is not a valid entry. Please try again: ");
            guess = input.nextInt();
        }
        else 
            if (guess > answer)
            {
                System.out.println("Too high, Try Again: ");
                guess = input.nextInt();
            }
            else 
                if (guess < answer)
                {
                    System.out.println("Too low, Try Again: ");
                    guess = input.nextInt();
                }
        input.nextLine();

    }
    while (guess != answer);

    System.out.println("Congratulations, You guessed the number!");
}

answered Oct 14, 2014 at 18:44

user2494817

6974 silver badges12 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Mac Over a year ago

This works but I have a few questions. At the end of the do/while in inputGuess you have included input.nextLine(); Why is that? I don't have it in my code and it works fine.

Mac Over a year ago

Also why do you have to initialize the the playAgain string in main with "";

user2494817 Over a year ago

@macattack The input.nextLine() was put in to solve the catch of the return character (\n), it may work without it... and i initialized the playAgain string within main to "" for the sake of initializing it... no specific reason.

afzalex · Accepted Answer · 2014-10-14 19:02:08Z

2

Do the following and your code will work :

Replace all input.nextInt(); with Integer.parseInt(input.nextLine());
Replace (playAgain == "Y" || playAgain == "y") with (playAgain.equalsIgnoreCase("Y"))
Initialise answer inside inputGuess() in starting instead.
Replace the body of if(playAgain.equalIgnoreCase("Y")) with inputGuess();

When you enter integer value through console it also contain a \n(next line) in it. But when you use nextInt(), it doesn't read this \n, but then when you tried to get next line with input.nextLine(), it looks for \n(next line) which is already there from integer entry and having nothing after that. Code look for "Y" or "y" and breaks because it doesn't found any of them.

That is why Integer.parseInt(input.nextLine()); works here

edited Oct 14, 2014 at 19:02

answered Oct 14, 2014 at 18:37

afzalex

8,6602 gold badges39 silver badges66 bronze badges

Comments

Rafael R. S. Robles · Accepted Answer · 2014-10-14 20:10:36Z

1

Here is the code:

private Random num = new Random();

private int answer = num.nextInt(10) +1;

private int guess;

private String playAgain;

Scanner input = new Scanner(System.in);

public void inputGuess(){
    System.out.println("Enter a number between 1 and 10 as your first guess: ");

    guess = input.nextInt();
    do{
        if (guess < 1 || guess > 10){
            System.out.println("That is not a valid entry. Please try again: ");
            guess = input.nextInt();
        }else if (guess > answer){
            System.out.println("Too high, Try Again: ");
            guess = input.nextInt();
        }else if (guess < answer){
            System.out.println("Too low, Try Again: ");
            guess = input.nextInt();
        }

        if(guess == answer) {
            System.out.println("Congratulations, You guessed the number!");
            System.out.println("Would you like to play again? Enter Y to play or any other key to quit: ");
            playAgain = input.nextLine();
        }

    }while (!playAgain.equals("Y") && !playAgain.equals("y"));
}

You just need to introduce the winning/losing logic inside the while, and the condition will be the ending/continue flag.

Another thing is always remember when comparing strings to use the equals method, since the == will compare the object reference and not the String value, in some cases == will return true for equal string since how JVM stores the Strings, but to be sure always use equals.

edited Oct 14, 2014 at 20:10

answered Oct 14, 2014 at 18:31

Rafael R. S. Robles

8977 silver badges20 bronze badges

2 Comments

Alvin Bunk Over a year ago

Your code doesn't check is random is from "1 to 10". In this case answer can be from "0 to 9".

Rafael R. S. Robles Over a year ago

You are right Alvin, to make it from "1 to 10" we need to add 1, I will edit the answer. Thanks!

brso05 · Accepted Answer · 2014-10-14 18:31:54Z

Try something like this:

public void inputGuess(){
        System.out.println("Enter a number between 1 and 10 as your first guess: ");
        Scanner input = new Scanner(System.in);
        guess = input.nextInt();
        playAgain = "Y";
        do{
        if (guess < 1 || guess > 10){
            System.out.println("That is not a valid entry. Please try again: ");
            guess = input.nextInt();
        }else if (guess > answer){
            System.out.println("Too high, Try Again: ");
            guess = input.nextInt();
        }else if (guess < answer){
            System.out.println("Too low, Try Again: ");
            guess = input.nextInt();
        }

        if(guess == answer)
        {
            System.out.println("Congratulations, You guessed the number!");
            System.out.println("Would you like to play again? Enter Y to play or N to quit: ");
            input.nextLine();
            playAgain = input.next();
            answer = num.nextInt(10);
            guess = -1;
            if(!playAgain.equalsIgnoreCase("N"))
            {
                System.out.println("Enter a number between 1 and 10 as your first guess: ");
                guess = input.nextInt();
            }
        }

        }while (!playAgain.equalsIgnoreCase("N"));

    }

You need your code for checking if they want to play again inside the loop. This way you wait until they have guessed the number correctly then ask if they want to play again. If they do you restart the process if they don't you exit the loop.

Alvin Bunk · Accepted Answer · 2014-10-14 18:37:07Z

0

Some of the solution I see above aren't correct. The random number, you need to add 1 to get between 1 and 10, also you need to compare with equals. I use case insensitive here.

The following code works as you need it.

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

public class Test2 {
    private static Random num = new Random();
    private static int answer = 0;
    private static int guess;
    private static String playAgain;

    public static void main(String[] args) {
        inputGuess();
    }

    // Guess Method.
    public static void inputGuess(){
        // create answer.
        answer = 1+ num.nextInt(10);

        System.out.println("Enter a number between 1 and 10 as your first guess: ");
        Scanner input = new Scanner(System.in);
        guess = input.nextInt(); 
        do{
        if (guess < 1 || guess > 10){
            System.out.println("That is not a valid entry. Please try again: ");
            guess = input.nextInt();
        }else if (guess > answer){
            System.out.println("Too high, Try Again: ");
            guess = input.nextInt();
        }else if (guess < answer){
            System.out.println("Too low, Try Again: ");
            guess = input.nextInt();
        }

        }while (guess != answer);

        System.out.println("Congratulations, You guessed the number!");
        System.out.println("Would you like to play again? Enter Y to play or any other key to quit: ");
        playAgain = input.nextLine();
        if( playAgain.equalsIgnoreCase("Y") ){ 
            inputGuess();
        }

    }
}

answered Oct 14, 2014 at 18:37

Alvin Bunk

7,8123 gold badges31 silver badges48 bronze badges

2 Comments

Alvin Bunk Over a year ago

What do you mean @user2494817? Why is recursion a bad idea for the if statement?

afzalex Over a year ago

@user2494817 Using recursion should be avoided as much as possible. But in OP's case I think there is no issue. The OP's code will change too much if not done that. And speed is not an issue here. It is just a simple program.

Tirath · Accepted Answer · 2014-10-14 20:20:32Z

By now, you would have already guessed the right way to do it. Here is how I will approach it

public class Test {
    public static void main (String...a) {
        inputGuess();
    }
    public static void inputGuess() {

        Scanner input = new Scanner(System.in);
        String playAgain = "Y";
        int guess;
        Random ran = new Random();
        int answer = ran.nextInt(10) + 1;
        while (playAgain.equalsIgnoreCase("Y")) {
            System.out.println("Enter a number between 1 and 10 as your first guess: " + answer);
            guess = input.nextInt(); 
            do {
                if (guess < 1 || guess > 10) {
                    System.out.println("That is not a valid entry. Please try again: ");
                    guess = input.nextInt();
                } else if (guess > answer) {
                    System.out.println("Too high, Try Again: ");
                    guess = input.nextInt();
                } else if (guess < answer) {
                    System.out.println("Too low, Try Again: ");
                    guess = input.nextInt();
                }
            } while (guess != answer);

            System.out.println("Congratulations, You guessed the number!");
            System.out.println("Would you like to play again? Enter Y to play or any other key to quit: ");
            input.nextLine();
            playAgain = input.nextLine();
            answer = ran.nextInt(10) + 1
        }           
    }
}

madhu_karnati · Accepted Answer · 2014-10-15 12:41:59Z

This code can serve your purpose...

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

public class GuessingGame 
{
private Random num = new Random();
private int answer ;
private int guess;
private String playAgain;

public void inputGuess() 
{         
    answer = num.nextInt(11);
    System.out.println("Enter a number between 1 and 10 as your first guess: ");
    Scanner input = new Scanner(System.in);
    guess = input.nextInt();
    do {            
        if (guess < 1 || guess > 10) {
            System.out
                    .println("That is not a valid entry. Please try again: ");
            guess = input.nextInt();
        } else if (guess > answer) {
            System.out.println("Too high, Try Again: ");
            guess = input.nextInt();
        } else if (guess < answer) {
            System.out.println("Too low, Try Again: ");
            guess = input.nextInt();
        }

    } while (guess != answer);

    System.out.println("Congratulations, You guessed the number!");
    System.out.println("Would you like to play again? Enter Y to play or any other key to quit: ");
    do
    {           
        playAgain = input.nextLine();

    }while(playAgain.length()<1);

    if (playAgain.trim().equalsIgnoreCase("y"))
    {
        inputGuess();           
    }
    else
    {
        System.out.println("Good Bye!!!");
    }

}

public static void main(String[] args) {
    new GuessingGame().inputGuess();
}
   }

Kick Buttowski · Accepted Answer · 2014-10-19 06:58:35Z

0

one issue :

Do not compare the content of two strings by == which just you should use equals()

Imagine the right answer is one in this case

Follow this as your blue print sample

  int answer = 0;
  String yes = "";
  Scanner input = new Scanner(System.in);
  do{
    do{
        System.out.println("Enter your number");
        answer = input.nextInt();
  } while ( answer != 1);
      System.out.println("Would you like to play again?");
      yes = input.next();
  } while ( yes.equalsIgnoreCase("yes"));

output:

enter image description here

edited Oct 19, 2014 at 6:58

answered Oct 14, 2014 at 18:26

Kick Buttowski

6,74713 gold badges39 silver badges61 bronze badges

1 Comment

Kick Buttowski Over a year ago

@SamIam is it better now?

Collectives™ on Stack Overflow

User input to repeat program in Java

8 Answers 8

3 Comments

Comments

2 Comments

Comments

2 Comments

Comments

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

8 Answers 8

3 Comments

Comments

2 Comments

Comments

2 Comments

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related