So I'm trying to add a loop to this program that will display an error message to the user if they enter a color that isn't red, green, blue, orange, or yellow. I'm just not sure on how to do so. I've tried adding a while loop in the userColorChoice method, but it just creates an infinite loop - so I'm doing something wrong. Thank you!

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

public class ESP 

{  
    public static void main(String[] args)
    {
        int correct = 0, incorrect = 0;
        for(int i = 1; i <= 10; i  )
        {
            if(userColorChoice().equalsIgnoreCase(computerColorChoice()))
            {
                System.out.println("You guessed correctly!");
                correct  ;
            }
            else
            {
                System.out.println("Sorry, your guess was wrong!");
                incorrect  ;
            }
        }
        System.out.println("Amount of times you guessed correctly: "   correct);
        System.out.println("Amount of times you guess incorrectly: "   incorrect);
    }

    public static String userColorChoice()
    {
        Scanner keyboard = new Scanner(System.in);
        System.out.print("Choose either red, green, blue, orange or yellow! ");
        String userColorChoice = keyboard.nextLine();

        System.out.println("You chose: "   userColorChoice);
        return userColorChoice;
    }

    public static String computerColorChoice()
    {
        String randomColor;
        int randomNumber;

        Random random = new Random();
        randomNumber = random.nextInt(4);

        switch (randomNumber)
        {
            case 0:
                randomColor = "Red";
                break;
            case 1:
                randomColor = "Green";
                break;
            case 2:
                randomColor = "Blue";
                break;
            case 3:
                randomColor = "Orange";
                break;
            case 4:
                randomColor = "Yellow";
                break;
            default:
                randomColor = " ";
        }

        System.out.println("The computer chose: "   randomColor);
        return randomColor;
    }

}

CodePudding user response：

I would suggest you introduce an enum COLOR

Also change the computerColorChoice method to something like below, this way you do not have to add the code every time you add a new color

I added this new line to COLOR.valueOf(capitaliseFirstLetter(userColorChoice)); if userColorChoice not one of the colors this would throw IllegalArgumentException that is being handled in main method catch block

     public static void main(String[] args) {
        int correct = 0, incorrect = 0, i = 0;
        while (i < 10) {
            try {
                if (userColorChoice().equalsIgnoreCase(computerColorChoice())) {
                    System.out.println("You guessed correctly!");
                    correct  ;
                } else {
                    System.out.println("Sorry, your guess was wrong!");
                    incorrect  ;
                }
                i  ;
            } catch (IllegalArgumentException e) {
                System.out.println("invalid choice");
            }
        }
        System.out.println("Amount of times you guessed correctly: "   correct);
        System.out.println("Amount of times you guess incorrectly: "   incorrect);
    }

    public static String userColorChoice() {
        Scanner keyboard = new Scanner(System.in);
        System.out.print("Choose either red, green, blue, orange or yellow! ");
        String userColorChoice = keyboard.nextLine();
        COLOR.valueOf(capitaliseFirstLetter(userColorChoice));
        System.out.println("You chose: "   userColorChoice);
        return userColorChoice;
    }

    private static String capitaliseFirstLetter(String choice) {
        return choice.substring(0, 1).toUpperCase()   choice.toLowerCase().substring(1);
    }

    public static String computerColorChoice() {
        COLOR[] colors = COLOR.values();
        return colors[new Random().nextInt(colors.length)].name();
    }

    enum COLOR {
        Red, Green, Blue, Orange, Yellow;
    }

CodePudding user response：

I'd use a List<String> to hold the colors. This will make both user validation and computer selection much easier:

import java.util.*;
class Main {

  public static Random random = new Random();
  public static Scanner keyboard = new Scanner(System.in);
  public static List<String> colors = Arrays.asList("RED", "GREEN", "BLUE", "ORANGE", "YELLOW");
  
  public static void main(String[] args)
  {
      int correct = 0, incorrect = 0;
      for(int i = 1; i <= 10; i  )
      {
          if(userColorChoice().equalsIgnoreCase(computerColorChoice()))
          {
              System.out.println("You guessed correctly!");
              correct  ;
          }
          else
          {
              System.out.println("Sorry, your guess was wrong!");
              incorrect  ;
          }
      }
      System.out.println("Amount of times you guessed correctly: "   correct);
      System.out.println("Amount of times you guess incorrectly: "   incorrect);
  }

  public static String userColorChoice()
  {          
      String userColorChoice;
      do {
        System.out.print("Choose either red, green, blue, orange or yellow! ");
        userColorChoice = keyboard.nextLine().toUpperCase();;
      } while (colors.indexOf(userColorChoice) == -1);
            
      System.out.println("You chose: "   userColorChoice);
      return userColorChoice;
  }

  public static String computerColorChoice()
  {
      String randomColor = colors.get(random.nextInt(colors.size()));
      System.out.println("The computer chose: "   randomColor);
      return randomColor;
  }
  
}