Handling Invalid Input in Rock Paper Scissors Game

General Discussions
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1

What is the best way to handle invalid user input in a Rock Paper Scissors Java game? I’m new to programming and have written a simple game that runs fine, but I want to display a message like “Invalid move. Try again.” if the user enters an incorrect character (anything other than ‘R’, ‘P’, or ‘S’). For example, if the user inputs ‘Q’, the program should print "Invalid move." How can I implement this properly?

2

When you’re handling invalid user input in your rock paper scissors java game, the simplest approach would be to check if the input is one of the valid moves before proceeding with the game logic. You can use an if-condition like this:

if (!personPlay.equals("R") && !personPlay.equals("P") && !personPlay.equals("S")) {
    System.out.println("Invalid move. Try again.");
} else {
    // Continue with the game logic
}

This ensures that if the user enters an invalid character (say, “Q”), they’ll be told to try again. It’s a good starting point for beginners.

3

That’s a solid approach, Babita! If you’re aiming for a more user-friendly experience, you could take it a step further by using a loop that keeps asking the user until they enter a valid move. This avoids having to restart the game just for a typo. Here’s how you can implement it:

while (!personPlay.equals("R") && !personPlay.equals("P") && !personPlay.equals("S")) {
    System.out.println("Invalid move. Try again.");
    personPlay = scan.next().toUpperCase();
}

This will continuously prompt the user until they enter one of the valid moves, keeping the game flowing smoothly. Definitely an improvement for a better experience in rock paper scissors java.

4

Great additions, Devan! If you’re looking for a more scalable and cleaner approach, especially as your game grows or if you want to add more valid moves (like “Lizard” or “Spock” :wink:), I recommend using a Set to store valid moves. It’s much more readable and efficient:

import java.util.Set;

Set<String> validMoves = Set.of("R", "P", "S");
if (!validMoves.contains(personPlay)) {
    System.out.println("Invalid move. Try again.");
} else {
    // Continue with the game
}

This approach makes your code cleaner and more flexible. Plus, it’s easier to modify when you decide to expand the rock paper scissors java game with additional moves in the future.

5

Invalid Input Handling: If the user types something that’s not ‘rock’, ‘paper’, or scissors’, we show an error message . Tie Condition: If both choices are the same, it’s a tie. Winning and Losing Conditions: Using nested if statements, we compare the Spacebar clicker user’s choice with the computer’s choice to decide the winner. The problem is that it sometimes reads “scissors” as an invalid input, which seems to me completely randomly and i dont know what the problem is.

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