java - 如何循环主类

Question

如果用户想要但不确定如何，我正在尝试让我的石头剪刀布应用程序循环。我正在上编程课，但我在上次尝试修复代码时破坏了代码，并设法恢复到之前的状态。

public static void main(String[] args)
    {
    Scanner scan = new Scanner(System.in);
    String playAgain = "Y";

    while (playAgain.equals("Y") || playAgain.equals("y"))
        {
        String playerChoice = "";
        while (!playerChoice.equals("R") && !playerChoice.equals("P") && !playerChoice.equals("S"))
            {
            System.out.println("Please enter a correct character\n (R)ock, (P)aper, or (S)cissors.");
            playerChoice = scan.next();

         //Player choice to upper case to minimize the number of wrong inputs//
            playerChoice = playerChoice.toUpperCase();
            }

        int randNum = (int) (Math.random() * 3);
        String compChoice = "";
        switch (randNum)
            {
            case 0:
                compChoice = "R";
                break;
            case 1:
                compChoice = "P";
                break;
            case 2:
                compChoice = "S";
                break;
            }
        System.out.println("The computer chose: " + compChoice);

        if (playerChoice.equals(compChoice))
            {
            System.out.println("It's a Tie!");
            } else if (playerChoice.equals("R") && compChoice.equals("S") || playerChoice.equals("P") && compChoice.equals("R") || playerChoice.equals("S") && compChoice.equals("P"))
            {
            System.out.println("You Win!");
            } else
            {
            System.out.println("You Lose");
            }
        System.out.println("Would you like to play again?\n(Y or N)");
        playAgain = scan.nextLine();
        if (playAgain.equals("N"))
            {
            break;
            }
        }
    }

Answer 1

解决方案是您的扫描方法调用之间需要达成一致。

要么两者都应该是 nextLine，要么两者都应该是 next。

顺便说一句 - 我非常喜欢在字符串比较中使用 .equalsIgnoreCase 而不是 .equals，因为它使代码简单且易于阅读。 (例如，您可以跳过 toUpperCase 以及额外的条件)

<小时/>

至于扫描仪为什么/到底在做什么导致这个问题，这是更详细和复杂的。