How do I stop this loop from repeating once the user has entered the correct answer?

Question

I'm only just beginning to learn to code in java and I've tried to figure this out for a while now, I've tried various methods and I've tried looking through similar questions but I can't find my answer.

I'm trying to get the loop to repeat while the user's input does not equal to 1, 2, or 3. Then stop repeating once a correct answer is entered.

    // create a menu and display it to the user
    // then ask the user to choose an option
    String menu = "1) See Rules\n"
                + "2) Play the Game\n"
                + "3) Exit\n"
                + "Please enter your choice: (1 or 2 or 3) ";

    String userChoice = JOptionPane.showInputDialog(menu);

    JOptionPane.showMessageDialog(null, "You chose option " + userChoice); 

    // display the rules
    String rules = "Rules:\n"

            + "The game will display total 3 multiple choice questions," +
            " with 4 possible answers per question.\n"
            + "Once you answer the question, the correct answer will be displayed" +
            " and the game will advance to the next question.\n"
            + "If you answer the question correctly, you will gain a point.\n"
            + "Each point is added to a total score that will be displayed at the" + 
            "end of the game.\n";

 // declare an integer that reads the user input
 int numericChoice = Integer.parseInt(userChoice);

 boolean valid = (numericChoice == 1 || numericChoice == 2 || numericChoice == 3);

 while (true)
 {
     if (!valid) {
         JOptionPane.showMessageDialog(null, "Invalid selection, please try again");
         JOptionPane.showInputDialog(menu);
     } if (valid){ 
         break;
 }

    if (numericChoice == 1){
     // display the rules then start the game
    JOptionPane.showMessageDialog(null, rules);
    }
    else if (numericChoice == 2){
     // start the game
    JOptionPane.showMessageDialog(null, "Let's play the game.\n");
    }
    else if (numericChoice == 3)
     // exit the game
    System.exit(0);

Please help.

Answer 1

Your problem is that you are computing valid outside of your loop. In other words: you compute it once; before you enter the loop; and then, within your loop you never touch its value again.

Therefore, the "only" thing that your loop does is to raise that dialog over and over again.

Thus: you have to move all of those computations inside the loop!

So, not only

boolean valid = (numericChoice == 1 || numericChoice == 2 || numericChoice == 3);

needs to go into the loop, but also the code that fetches the user inputs, and determines numericChoice !

What you could do would be to write a helper method, like:

private int showMenuAndGetUserChoice() {
 // create a menu and display it to the user
 // then ask the user to choose an option
 String menu = "1) See Rules\n" ...
 String userChoice = JOptionPane.showInputDialog(menu);
 JOptionPane.showMessageDialog(null, "You chose option " + userChoice); ...

 return Integer.parseInt(userChoice);
} 

And now you can loop much easier, by simply calling that method and checking its result within your loop body!