Question

Please help I am struggling with this and 3*Math.random())+1; and how to use it within the program

For this project you will write a Java program that will play a simple game of Rock, Paper, Scissors.  If you have never played this game before the rules are simple - each player chooses one of Rock, Paper or Scissors and they reveal their choices simultaneously.
• The choice of Rock beats the choice of Scissors ("Rock smashes Scissors")
• The choice of Scissors beats the choice of Paper ("Scissors cut Paper")
• The choice of Paper beats Rock ("Paper covers rock")
• If both players choose the same item, they tie
to extract the character from the string. One of the PowerPoint slides in section 2 showed this.
• Get a random number (value 1, 2 or 3) in the following manner:
o int compVal = (int) (3*Math.random()) + 1; • You may use the letters themselves to represent the R, P, S values or you may change
them to integers 1, 2, or 3. Your choice, but remember that you have to deal with both upper and lower case characters. (Check out the to.Upper method for assistance if you need it.)
• You could use the R, P or S that the user enters and the 1, 2 or 3 the computer generates
directly if you want to. That may be the easiest way to write it, but don’t forget to make sure to use a consistent mapping between the letters and numbers or you will be really confused.
Sample Output:
Rock, Paper, Scissors-Enter a choice R/P/S: r We both chose the same item-try again
Rock, Paper, Scissors-Enter a choice R/P/S: r I chose Paper and you chose Rock: Paper covers Rock, so I win
Rock, Paper, Scissors-Enter a choice R/P/S: r
I chose Scissors and you chose Rock: Rock breaks Scissors, so you win Rock, Paper, Scissors-Enter a choice R/P/S: p
Your program will generate a random choice of Rock, Paper or Scissors.  It should then prompt the user for their choice.  It should report both choices and indicate who wins the game.  In addition, it should check the user's input and if the user inputs an invalid choice it should display an error message and end. Hints:
• Remember that to input a char value you read it as a string and use the charAt method

Answer 1

The Java code is given below:

import java.util.Scanner;

public class RPS {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        String user,my;
        char userChoice, myChoice;
        while(true) {
            /**
             * Generating random number and get corresponding character(R/P/S)
             */
            int compVal = (int) (3*Math.random()) + 1;
            if(compVal == 1)
                myChoice = 'R';
            else if(compVal == 2)
                myChoice = 'P';
            else
                myChoice = 'S';
            /**
             * Input user's choice
             */
            System.out.print("Rock, Paper, Scissors-Enter a choice R/P/S: ");
            user = scan.nextLine();
            userChoice = Character.toUpperCase(user.charAt(0));
            /**
             * Print error message on Invalid choice 
             */
            if(userChoice != 'R' && userChoice != 'P' && userChoice != 'S')
            {
                System.out.println("Invalid Choice!");
                break;
            }
            /**
             *  Comparing and printing results
             */
            if(myChoice == userChoice)
                System.out.println("We both chose the same item-try again");
            else if(myChoice == 'R' && userChoice == 'P') {
                System.out.println("I chose Rock and you chose Paper: Paper covers Rock, so You win");
            }
            else if(myChoice == 'P' && userChoice == 'R') {
                System.out.println("I chose Paper and you chose Rock: Paper covers Rock, so I win");
            }
            else if(myChoice == 'R' && userChoice == 'S') {
                System.out.println("I chose Rock and you chose Scissors: Rock breaks Scissors, so I win");
            }
            else if(myChoice == 'S' && userChoice == 'R') {
                System.out.println("I chose Scissors and you chose Rock: Rock breaks Scissors, so you win");
            }
            else if(myChoice == 'P' && userChoice == 'S') {
                System.out.println("I chose Paper and you chose Scissors: Scissors cut Paper, so you win");
            }
            else if(myChoice == 'S' && userChoice == 'P') {
                System.out.println("I chose Scissors and you chose Paper: Scissors cut Paper, so I win");
            }
        }
    }
}

Sample Output:

Screenshot of java code is given below:

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