不能得到一段时间，或者做... while 循环工作，查找多个答案。没有任何作用

Question

除了循环之外的一切都有效，当被问及我是否想再玩一次时，输入 "y" 或 "n" 它会抛出一个我无法弄清楚的错误。

如果此代码格式不正确，请原谅，这是复制和粘贴。

/* © Tucker Fowler 2015
 */
package rpslizardspock;

import java.util.Scanner;
import java.util.Random;

/**
 *
 * @author Tucker
 */
public class RpsLizardSpock {


public static void main(String[] args) {

    String userChoice;
    boolean goAgain;
    boolean y = true;
    boolean n = false;

    Scanner sc = new Scanner(System.in);
    Random ra = new Random();
    while (goAgain = y) {

        System.out.println("Welcome to Rock, Paper, Scissors, Lizard, Spock\n\n"
                + "Please make a Choice: ");
        userChoice = sc.nextLine();

        String ucConv = userChoice.toUpperCase();

        System.out.println("You Chose: " + userChoice);

        int cpuChoice = ra.nextInt(5) + 1;

        if ((cpuChoice == 1) && (((ucConv.equals("LIZARD"))) || ((ucConv.equals("SCISSORS"))))) {
            System.out.println("\n\nComputer chose Rock, You Lose");
        } else if ((cpuChoice == 1) && (((ucConv.equals("PAPER"))) || ((ucConv.equals("SPOCK"))))) {
            System.out.println("\n\nComputer chose Rock, You Win");
        } else if ((cpuChoice == 2) && (((ucConv.equals("SPOCK"))) || ((ucConv.equals("ROCK"))))) {
            System.out.println("\n\nComputer chose Paper, You Lose");
        } else if ((cpuChoice == 2) && (((ucConv.equals("SCISSORS"))) || ((ucConv.equals("LIZARD"))))) {
            System.out.println("\n\nComputer chose Paper, You Win");
        } else if ((cpuChoice == 3) && (((ucConv.equals("LIZARD"))) || ((ucConv.equals("PAPER"))))) {
            System.out.println("\n\nComputer chose Scissors, You Lose");
        } else if ((cpuChoice == 3) && (((ucConv.equals("SPOCK"))) || ((ucConv.equals("ROCK"))))) {
            System.out.println("\n\nComputer chose Scissors, You Win");
        } else if ((cpuChoice == 4) && (((ucConv.equals("SPOCK"))) || ((ucConv.equals("PAPER"))))) {
            System.out.println("\n\nComputer chose Lizard, You Lose");
        } else if ((cpuChoice == 4) && (((ucConv.equals("SCISSORS"))) || ((ucConv.equals("ROCK"))))) {
            System.out.println("\n\nComputer chose Lizard, You Win");
        } else if ((cpuChoice == 5) && (((ucConv.equals("ROCK"))) || ((ucConv.equals("SCISSORS"))))) {
            System.out.println("\n\nComputer chose Spock, You Lose");
        } else if ((cpuChoice == 5) && (((ucConv.equals("PAPER"))) || ((ucConv.equals("LIZARD"))))) {
            System.out.println("\n\nComputer chose Spock, You Win");
        } else if ((cpuChoice == 1) && (ucConv.equals("ROCK"))) {
            System.out.println("\n\nComputer chose Rock also, Draw");
        } else if ((cpuChoice == 2) && (ucConv.equals("PAPER"))) {
            System.out.println("\n\nComputer chose Paper also, Draw");
        } else if ((cpuChoice == 3) && (ucConv.equals("SCISSORS"))) {
            System.out.println("\n\nComputer chose Scissors also, Draw");
        } else if ((cpuChoice == 4) && (ucConv.equals("LIZARD"))) {
            System.out.println("\n\nComputer chose Lizard also, Draw");
        } else if ((cpuChoice == 5) && (ucConv.equals("SPOCK"))) {
            System.out.println("\n\nComputer chose Spock also, Draw");
        }
        System.out.println("\n\n Would you like to play again? y/n");
        goAgain = sc.nextBoolean();
    }
}

}

我得到的错误是：

Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Scanner.java:909)
    at java.util.Scanner.next(Scanner.java:1530)
    at java.util.Scanner.nextBoolean(Scanner.java:1825)
    at rpslizardspock.RpsLizardSpock.main(RpsLizardSpock.java:73)
Java Result: 1

Answer 1

Scanner.nextBoolean() 查找 "true" 或 "false"，而不是 "y" 或 "n".

改为尝试以下方法：

goAgain=sc.next().equalsIgnoreCase("y");

这样，如果他们输入y，goAgain就变成真，否则就变成假。

此外，正如克里斯提到的，= 表示赋值。此外，您还没有为 goAgain 赋值。因此，您应该像这样给布尔值赋值

boolean goAgain=true;//true so that you can enter the loop in the first place

对于你的循环，你真的想说（而我想再说一次）

while(goAgain){...}

最后，不要将 nextLine() 与 nextInt() 和 next() 等其他东西一起使用。我建议您将 nextLine() 的使用更改为 next()，因为它只要求一个单词。

Answer 2

一般来说，当您使用 Scanner 时，始终调用 next() 或始终调用 nextLine() 最不容易出错。当我们使这两个一致时，修复赋值问题，并比较 y，然后代码可以正常工作。

import java.util.Scanner;
import java.util.Random;
public class RpsLizardSpock {
    public static void main(String[] args) {

        String userChoice;
        boolean goAgain = true;

        Scanner sc = new Scanner(System.in);
        Random ra = new Random();
        while (goAgain) {

            System.out.println("Welcome to Rock, Paper, Scissors, Lizard, Spock\n\n"
                    + "Please make a Choice: ");
            userChoice = sc.next();

            String ucConv = userChoice.toUpperCase();

            System.out.println("You Chose: " + userChoice);

            int cpuChoice = ra.nextInt(5) + 1;

            if ((cpuChoice == 1) && (((ucConv.equals("LIZARD"))) || ((ucConv.equals("SCISSORS"))))) {
                System.out.println("\n\nComputer chose Rock, You Lose");
            } else if ((cpuChoice == 1) && (((ucConv.equals("PAPER"))) || ((ucConv.equals("SPOCK"))))) {
                System.out.println("\n\nComputer chose Rock, You Win");
            } else if ((cpuChoice == 2) && (((ucConv.equals("SPOCK"))) || ((ucConv.equals("ROCK"))))) {
                System.out.println("\n\nComputer chose Paper, You Lose");
            } else if ((cpuChoice == 2) && (((ucConv.equals("SCISSORS"))) || ((ucConv.equals("LIZARD"))))) {
                System.out.println("\n\nComputer chose Paper, You Win");
            } else if ((cpuChoice == 3) && (((ucConv.equals("LIZARD"))) || ((ucConv.equals("PAPER"))))) {
                System.out.println("\n\nComputer chose Scissors, You Lose");
            } else if ((cpuChoice == 3) && (((ucConv.equals("SPOCK"))) || ((ucConv.equals("ROCK"))))) {
                System.out.println("\n\nComputer chose Scissors, You Win");
            } else if ((cpuChoice == 4) && (((ucConv.equals("SPOCK"))) || ((ucConv.equals("PAPER"))))) {
                System.out.println("\n\nComputer chose Lizard, You Lose");
            } else if ((cpuChoice == 4) && (((ucConv.equals("SCISSORS"))) || ((ucConv.equals("ROCK"))))) {
                System.out.println("\n\nComputer chose Lizard, You Win");
            } else if ((cpuChoice == 5) && (((ucConv.equals("ROCK"))) || ((ucConv.equals("SCISSORS"))))) {
                System.out.println("\n\nComputer chose Spock, You Lose");
            } else if ((cpuChoice == 5) && (((ucConv.equals("PAPER"))) || ((ucConv.equals("LIZARD"))))) {
                System.out.println("\n\nComputer chose Spock, You Win");
            } else if ((cpuChoice == 1) && (ucConv.equals("ROCK"))) {
                System.out.println("\n\nComputer chose Rock also, Draw");
            } else if ((cpuChoice == 2) && (ucConv.equals("PAPER"))) {
                System.out.println("\n\nComputer chose Paper also, Draw");
            } else if ((cpuChoice == 3) && (ucConv.equals("SCISSORS"))) {
                System.out.println("\n\nComputer chose Scissors also, Draw");
            } else if ((cpuChoice == 4) && (ucConv.equals("LIZARD"))) {
                System.out.println("\n\nComputer chose Lizard also, Draw");
            } else if ((cpuChoice == 5) && (ucConv.equals("SPOCK"))) {
                System.out.println("\n\nComputer chose Spock also, Draw");
            }
            System.out.println("\n\n Would you like to play again? y/n");
            goAgain = sc.next().charAt(0) == 'y';
        }
    }
}

不能得到一段时间，或者做... while 循环工作，查找多个答案。没有任何作用

Can't get a while, or do... while loop to work, looked up multiple answers. nothing works

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