what is the best way to use a for loop?

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March 2019

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105 time

1

This program is a guessing game in which you input a letter between a and j and try to guess the randomly chosen answer. It works correctly, but I want to use a for loop to encompass all three guesses instead of writing them all out separately. Any suggestions on how to start this?

import java.util.Scanner;
import java.lang.Math;
import java.util.Random;

class Guess{

public static void main( String[] args ){

    Scanner sc = new Scanner(System.in);

    System.out.println("I'm thinking of a letter in the range a to j. You have three guesses. ");

    for(int i = 0; i<3; i++){   //this is where I'm having trouble

        System.out.print("Enter your first guess: ");

        Random r = new Random();
        char i = (char)(r.nextInt(10) + 'a');
        char b = sc.next().charAt(0);
        if(b>i){
            System.out.println("Your guess is too high. ");

        } else if(b<i){
            System.out.println("Your guess is too low. ");

        } else if(b==i){
            System.out.println("You win! ");
            return;

        }

        System.out.print("Enter your second guess: ");
        b = sc.next().charAt(0);
        if(b>i){
            System.out.println("Your guess is too high. ");

        } else if(b<i){
                System.out.println("Your guess is too low. ");

        } else if(b==i){
            System.out.println("You win! ");
            return;

        }

        System.out.print("Enter your third guess: ");
        b = sc.next().charAt(0);
        if(b>i){
            System.out.println("Your guess is too high. ");

        } else if(b<i){
            System.out.println("Your guess is too low. ");

        } else if(b==i){
            System.out.println("You win! ");

            }
        if(b!=i){
            System.out.println("You lose. The letter was " +i+ ".");
        }

    }
}

5 answers

0

Map your letters into a List<> or ArrayList<> then use for-each loop

Check this answer for a simple example of how to use for-each loop:

0

you can use a nested loop. this part is basically the same, and can be in inner loop (of 3 iterations)

System.out.print("Enter your ... guess: ")
char b = sc.next().charAt(0);
if(b>i){
    System.out.println("Your guess is too high. ");

} else if(b<i){
    System.out.println("Your guess is too low. ");

} else if(b==i){
    System.out.println("You win! ");
    return;

}

but the System.out.print("Enter your ... guess: ") is different every iteration. You can create const array of string with the strings {"first", "second", "third"} and access the correct string by the index of the loop (use format string here...)

0

Here is a quick example with a loop to play again if the game is over

class Guess {

    public static void main(String[] args) {


        Scanner sc = new Scanner(System.in);
        Random r = new Random();
        char toGuess;
        char yourGuess;
        boolean playing = true;
        boolean lost = true;

        while(playing) {

            toGuess = (char) (r.nextInt(10) + 'a');
            System.out.println("NEW GAME");
            System.out.println("========");
            System.out.println("I'm thinking of a letter in the range a to j. You have three guesses. ");

            for (int j = 0; j < 3; j++) {
                switch (j) {
                    case 0:
                        System.out.print("Enter your first guess: ");
                        break;
                    case 1:
                        System.out.print("Enter your second guess: ");
                        break;
                    case 2:
                        System.out.print("Enter your third guess: ");
                        break;
                    default:
                        System.out.println("Something went wrong. Game is closing!");
                        System.exit(0);
                        break;
                }

                yourGuess = sc.next().charAt(0);

                if (yourGuess > toGuess) {
                    System.out.println("Your guess is too high.");
                } else if (yourGuess < toGuess) {
                    System.out.println("Your guess is too low. ");
                } else if (yourGuess == toGuess) {
                    System.out.println("You win! ");
                    lost = false;
                    break;
                }

            }

            if(lost==false){
                System.out.println("Sorry, you lost!");
            }
            System.out.print("Do you want to play again? (y=yes | n=no): ");
            if(!sc.next().equals("y")){
                playing=false;
            }

        }
    }
}
2

Store the character the user should guess in a variable outside the loop.

Then inside the loop ask them to attempt guess number i+1 where i is the loop counter (or you can change to using a 1 based index).

If execution continues after the loop then it means they lost.

Here is an example:

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

class Guess {

    public static void main(String[] args) {

        int maxGuesses = 3;

        System.out.println("I'm thinking of a letter in the range a to j. You have " + maxGuesses + " guesses. ");

        Random r = new Random();
        char i = (char) (r.nextInt(10) + 'a');

        Scanner sc = new Scanner(System.in);
        String[] guessDescription = { "First", "Second", "Third" };

        for (int g = 0; g < maxGuesses; g++) {
            // use predefined guess description for 1-3, otherwise a generic description that works for any number of guesses above 3
            if (g < guessDescription.length) {
                System.out.print("Enter your " + guessDescription[g] + " guess:");
            } else {
                       System.out.print("Enter guess #" + (g + 1) + ":");
                   }

            char b = sc.next().charAt(0);

            if (b > i) {
                System.out.println("Your guess is too high. ");

            } else if (b < i) {
                       System.out.println("Your guess is too low. ");
                   } else if (b == i) {
                              System.out.println("You win! ");
                              return;
                          }
        }
        System.out.println("You lose. The letter was " + i + ".");
    }
}
0

You just need to replace your line Enter your .... guess. Based on i, you should keep a mapping like
{ 0:First,1:Second,2:Third}

 Scanner sc = new Scanner(System.in);

System.out.println("I'm thinking of a letter in the range a to j. You have three guesses. ");

List < String > strList = new ArrayList <String> ( );
strList.add("FIRST");
strList.add("SECOND");
strList.add("THIRD");
Random r = new Random();
char randX = (char)(r.nextInt(10) + 'a');
for(int i = 0; i<3; i++){   //this is where I'm having trouble

    System.out.print("Enter your"+ strList.get(i)+ "  guess: ");
    char b = sc.next().charAt(0);
    if(b==i){
        System.out.println("You win! ");
        return;

    }
    else
    {
        if(b>randX)
        {
            System.out.println("Your guess is too high. ");
       } 
        else 
            System.out.println("Your guess is too low. ");

        if ( b !=randX && i==2 )
        {
            System.out.println("You lose. The letter was " + randX + ".");
        }
    }
}