在循环内生成数字

Question

我必须创建一个虚拟摇滚剪刀纸游戏程序。我已经弄清楚了大部分内容，但是在用户每次进入游戏时要生成1-3的随机数时遇到了问题。我将在下面显示两个类，首先是用户，然后是计算机类。任何帮助将不胜感激，谢谢。

用户：

    public String play()
{

    do{

    switch (userChoice) {
        case R:
        {
            System.out.println("You have chosen rock.");

            if (robot.getComputerChoice().equals(paper)){
                System.out.println("You lose! \nPaper covers rock!");
                numOfLosses ++;
            }

            else if (robot.getComputerChoice().equals(scissors)){
                System.out.println("You win! \nRock smashes scissors!");
                numOfWins ++;
            }
            else if (robot.getComputerChoice().equals(rock)){
                    System.out.println("Its a tie!");
                    numOfTies ++;
            }
            userChoice = result;
        }
            break;
        case P:
        {
            System.out.println("You have chosen paper.");

            if (robot.getComputerChoice().equals(rock)){
                System.out.println("You win! \nPaper covers rock!");
                numOfWins ++;
            }
            else if (robot.getComputerChoice().equals(scissors)){
                System.out.println("You lose! \nScissors cuts paper!");
                numOfLosses ++;
            }
            else if (robot.getComputerChoice().equals(paper)){
                    System.out.println("Its a tie!");
                    numOfTies ++;
            }
            userChoice = result;

        }
            break;
        case S:
        {
            System.out.println("You have chosen scissors.");

            if (robot.getComputerChoice().equals(rock)){
                System.out.println("You lose! \nRock smashes scissors!");
                numOfLosses ++;
            }
            else if (robot.getComputerChoice().equals(paper)){
                System.out.println("You win! \nScissors cuts paper!");
                numOfWins ++;
            }
            else if (robot.getComputerChoice().equals(scissors)){
                    System.out.println("Its a tie!");
                    numOfTies ++;
            }
            userChoice = result;
        }
            break;
        default:
            System.out.println("That input was invalid.");
            break;
    }

        Scanner scan = new Scanner(System.in);

        System.out.println("Lets play Rock, Paper, Sciccors!");
        System.out.println("(R)ock, (P)aper, or (S)cissors? 0 to end the game.");

        userChoice = scan.next();    
        userChoice = userChoice.toUpperCase();

    } while (!userChoice.equals(EXIT));

    System.out.println("Thanks for playing!");
    System.out.println("Number of wins: " + numOfWins + "\nNumber of losses: "
            + numOfLosses + "\nNumber of ties: " + numOfTies);

    total = numOfWins + numOfLosses + numOfTies;

    winPercentage = (numOfWins/total) * 100;

    System.out.printf(userName + "'s win percentage: %.2f", winPercentage);
    System.out.print("%");

    return result;

计算机：

    public Computer() {

    Random rand = new Random();

    Scanner scan = new Scanner(System.in);
    COMPUTERNAME = "Bob";

    while (){ // can't figure out what to do here.

        generateNumber = rand.nextInt(3)+1; // 1 to 3

    switch (generateNumber) {
        case 1:
            computerChoice = "rock";
            break;
        case 2:
            computerChoice = "paper";
            break;
        case 3:
            computerChoice = "scissors";
            break;
        default:
            break; 
        } 
    } 
} 


public String getComputerChoice()
    {
        return computerChoice;
    }


public String getComputerName()
    {    
        System.out.print("My name is ");
        System.out.print(COMPUTERNAME);
        System.out.println(", your computer opponent.");

        return COMPUTERNAME;
    }