Java代码打印异常中给出的消息，即使条件为'；这不是真的

我正在测试我的用户输入，以查看它是否有效。如果无效，则应抛出一个

IllegalArgumentException

。但是，无论我的输入是什么，都会抛出

gameLogic

函数前几行中的

IllegalArgumentException

。结果是程序打印出

“在这个游戏中，你只能输入石头、布、剪刀或-1。”

无论我输入什么

import java.util.Scanner;
import java.util.Random;
class RockPaperScissors
{
    private static double mUserWinCount = 0;
    private static double mCpuWinCount = 0;
    private static double mUserLossCount = 0;
    private static double mCpuLossCount = 0; 
    private static double mDrawCount = 0;
    private static double mGameCount = 0;
    private static String mCpuInput;
    private static String mUserInput;


    public static void main(String [] args)
    {

         try
         {
             gameLogic(cpuInput(),userInput());
         }
         catch(IllegalArgumentException iae)
         {
             System.out.println(iae.getMessage());
         }


    }

    static String cpuInput()
    {
        Random random = new Random (System.currentTimeMillis());
        int RandomNumber=random.nextInt(3);
        if (RandomNumber == 0)
        mCpuInput = "Rock";
        else if (RandomNumber == 1)
        mCpuInput = "Paper";
        else
        mCpuInput = "Scissors";

        return mCpuInput;
    }

    static String userInput()
    {
        System.out.println("Enter Rock, Paper or Scissors, enter -1 in order to exit:- ");
        mUserInput = new Scanner(System.in).next();

        return mUserInput;

    }

    static void gameLogic(String cpuInput, String userInput)
    {
      if(!userInput.equalsIgnoreCase("Rock") || !userInput.equalsIgnoreCase("Paper") || !userInput.equalsIgnoreCase("Scissors") || !userInput.equals("-1"))
      {
         throw new IllegalArgumentException("You're only permitted to enter Rock, Paper, Scissors or -1 in this game.\n");
      }    

      if(userInput.equals("-1"))
      {
          score();
          System.exit(0);
      }
      System.out.println("CPU entered "+cpuInput+", User entered "+userInput);  
      String [] args = new String[0];

      if(userInput.equalsIgnoreCase(cpuInput))
      {
          System.out.println("It's a draw!");
          mDrawCount++;
          mGameCount++;
      }
      if(userInput.equalsIgnoreCase("Rock") && cpuInput.equalsIgnoreCase("Scissors") || userInput.equalsIgnoreCase("Paper") && cpuInput.equalsIgnoreCase("Rock") || userInput.equalsIgnoreCase("Scissors") && cpuInput.equalsIgnoreCase("Paper"))
      {
         System.out.println("User wins!"); 
         mUserWinCount++; 
         mCpuLossCount++;
         mGameCount++;
      }  
      if(cpuInput.equalsIgnoreCase("Rock") && userInput.equalsIgnoreCase("Scissors") || cpuInput.equalsIgnoreCase("Paper") && userInput.equalsIgnoreCase("Rock") || cpuInput.equalsIgnoreCase("Scissors") && userInput.equalsIgnoreCase("Paper"))
      {
         System.out.println("CPU wins!"); 
         mCpuWinCount++; 
         mUserLossCount++;
         mGameCount++;
      }

      main(args);
    }



    static void score()
    { 
       if (mGameCount==0)
       {
          System.out.println("No games have been played..");
       }    
       else 
       {
           double userWinPercentage = (mUserWinCount / mGameCount) * 100;
           double userLossPercentage = (mUserLossCount / mGameCount) * 100;
           double cpuWinPercentage = (mCpuWinCount / mGameCount) * 100; 
           double cpuLossPercentage = (mCpuLossCount / mGameCount) * 100; 
           double drawPercentage = (mDrawCount/mGameCount) * 100;

           System.out.println("Number of Games Played- " + mGameCount);

           System.out.println("Number of Draws- "+ mDrawCount);
           System.out.println("Percentage of Draws "+ drawPercentage + "%");

           System.out.println("Number of Wins by User- " + mUserWinCount);
           System.out.println("User's Win Percentage- " + userWinPercentage + "%");
           System.out.println("Number of Losses by User- " + mCpuLossCount);
           System.out.println("User's Loss Percentage- " + userLossPercentage + "%");

           System.out.println("Number of Wins by CPU- " + mCpuWinCount);
           System.out.println("CPU's Win Percentage- " + cpuWinPercentage + "%");
           System.out.println("Number of Losses by CPU- " + mCpuLossCount);
           System.out.println("CPU's Loss Percentage- " + cpuLossPercentage + "%");
       } 
    }    

在这一行

if(!userInput.equalsIgnoreCase("Rock") || !userInput.equalsIgnoreCase("Paper") || !userInput.equalsIgnoreCase("Scissors") || !userInput.equals("-1"))

使用

&&

，而不是

|

†

您可以使用一种形式的真值表来了解原因：

|输入| A | B | C | D | |结果|&结果|
|------------+---+---+---+---+-----------|-----------|
|“岩石”| F | T | T | T | T | F |
|“纸”T | F | T | T | T | F|
|“剪刀”T | T | F | T | T | F|
|“-1”| T | T | F | T | F|
|“foo”T | T | T | T | T | T|

†但是，从设计的角度来看，您可能希望重新构造代码，要求用户在输入不正确时重复输入，而不仅仅是以异常终止游戏。

在这一行中

if(!userInput.equalsIgnoreCase("Rock") || !userInput.equalsIgnoreCase("Paper") || !userInput.equalsIgnoreCase("Scissors") || !userInput.equals("-1"))

使用

&&

，而不是

|

†

您可以使用一种形式的真值表来了解原因：

|输入| A | B | C | D | |结果|&结果|
|------------+---+---+---+---+-----------|-----------|
|“岩石”| F | T | T | T | T | F |
|“纸”T | F | T | T | T | F|
|“剪刀”T | T | F | T | T | F|
|“-1”| T | T | F | T | F|
|“foo”T | T | T | T | T | T|

†但是，从设计角度来看，您可能希望重新构造代码，要求用户在输入不正确时重复输入，而不仅仅是在出现异常时终止游戏

这句话总是对的。我们有三种可能性：

这个词既不是“石头”也不是“纸”（忽略案例）

这个词是“岩石”

这个词是“纸”

如果a），两个等式都将返回false，那么您将使用“NOT”它们！而你得到的是真的

如果b）你得到假| |真（=真）

如果c）你得到了真| |假（=真）

这句话总是对的。我们有三种可能性：

这个词既不是“石头”也不是“纸”（忽略案例）

这个词是“岩石”

这个词是“纸”

如果a），两个等式都将返回false，那么您将使用“NOT”它们！而你得到的是真的

如果b）你得到假| |真（=真）

---

如果c）得到TRUE | | FALSE（=TRUE）

我将展示一段重构代码，向您展示处理输入和主循环的替代方法

此代码对输入使用显式检查，在确保输入为小写后，在输入上使用

开关

。请注意，检查正确的用户输入应该放在游戏逻辑之外。你的游戏逻辑应该是：执行游戏的代码。如果你有两个CPU播放器呢

除此之外，它还包含许多编码提示，首先是注释：

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

class RockPaperScissors {
    // NOTE: prefer integers instead of doubles for counts
    private static int mUserWinCount = 0;
    private static int mCpuWinCount = 0;
    // NOTE: avoid double state
    // isn't user loss always identical to cpu win count?
    private static int mUserLossCount = 0;
    private static int mCpuLossCount = 0;
    private static int mDrawCount = 0;
    private static int mGameCount = 0;

    public static void main(String[] args) {

        // NOTE: always manage your resources
        try (Scanner scanner = new Scanner(System.in)) {

            // NOTE: never use recursion unless you cannot avoid it
            // prefer while loop over calling main)
            while (true) {
                String userInput = userInput(scanner);
                if (userInput.equals("-1")) {
                    score();
                    // NOTE: prefer running out of main over calling exit
                    break;
                }

                // NOTE: bring back the amount of state ASAP!
                // just lowercase has less state, enums have even less
                if (!validChoice(userInput)) {
                    System.out.println("Not a valid choice!");
                    continue;
                }

                try {
                    String cpuInput = cpuInput();
                    gameLogic(cpuInput, userInput);
                } catch (IllegalArgumentException iae) {
                    System.out.println(iae.getMessage());
                }
            }
        }
    }

    // NOTE: use explicit checks for user input
    static boolean validChoice(String userChoice) {
        switch (userChoice.toLowerCase()) {
        case "paper":
        case "scissors":
        case "rock":
            return true;
        default:
            return false;
        }
    }

    static String cpuInput() {
        // NOTE: only define your variables in the scope where they are needed
        // this doesn't need to be a field
        String mCpuInput;

        // NOTE: prefer new SecureRandom() over Random if performance is not
        // essential
        Random random = new Random(System.currentTimeMillis());
        int RandomNumber = random.nextInt(3);
        if (RandomNumber == 0)
            mCpuInput = "Rock";
        else if (RandomNumber == 1)
            mCpuInput = "Paper";
        else
            mCpuInput = "Scissors";

        return mCpuInput;
    }

    static String userInput(Scanner scanner) {
        String mUserInput;
        System.out
                .println("Enter Rock, Paper or Scissors, enter -1 in order to exit:- ");
        mUserInput = scanner.next();
        return mUserInput;

    }

    static void gameLogic(String cpuInput, String userInput) {
        // NOTE: use logging instead for debug statements
        System.out.println("CPU entered " + cpuInput + ", User entered "
                + userInput);

        // NOTE: learn to detect code smell...
        // if you don't really need args you should not have to define it
        // String [] args = new String[0];

        if (userInput.equalsIgnoreCase(cpuInput)) {
            // NOTE: don't mix input/output with the actual game rules
            // return the outcome and then print instead (not fixed)
            System.out.println("It's a draw!");
            mDrawCount++;
            mGameCount++;
        }

        if (userInput.equalsIgnoreCase("Rock")
                && cpuInput.equalsIgnoreCase("Scissors")
                || userInput.equalsIgnoreCase("Paper")
                && cpuInput.equalsIgnoreCase("Rock")
                || userInput.equalsIgnoreCase("Scissors")
                && cpuInput.equalsIgnoreCase("Paper")) {
            System.out.println("User wins!");
            mUserWinCount++;
            mCpuLossCount++;
            mGameCount++;
        }
        if (cpuInput.equalsIgnoreCase("Rock")
                && userInput.equalsIgnoreCase("Scissors")
                || cpuInput.equalsIgnoreCase("Paper")
                && userInput.equalsIgnoreCase("Rock")
                || cpuInput.equalsIgnoreCase("Scissors")
                && userInput.equalsIgnoreCase("Paper")) {
            System.out.println("CPU wins!");
            mCpuWinCount++;
            mUserLossCount++;
            mGameCount++;
        }

        // NOTE: avoid recursion
        // don't do this, if you do *document*
        // main(args);
    }

    static void score() {
        if (mGameCount == 0) {
            System.out.println("No games have been played..");
        } else {
            double userWinPercentage = (mUserWinCount / mGameCount) * 100;
            double userLossPercentage = (mUserLossCount / mGameCount) * 100;
            double cpuWinPercentage = (mCpuWinCount / mGameCount) * 100;
            double cpuLossPercentage = (mCpuLossCount / mGameCount) * 100;
            double drawPercentage = (mDrawCount / mGameCount) * 100;

            // NOTE: learn about printf when the time comes
            System.out.println("Number of Games Played- " + mGameCount);

            System.out.println("Number of Draws- " + mDrawCount);
            System.out.println("Percentage of Draws " + drawPercentage + "%");

            System.out.println("Number of Wins by User- " + mUserWinCount);
            System.out.println("User's Win Percentage- " + userWinPercentage
                    + "%");
            System.out.println("Number of Losses by User- " + mCpuLossCount);
            System.out.println("User's Loss Percentage- " + userLossPercentage
                    + "%");

            System.out.println("Number of Wins by CPU- " + mCpuWinCount);
            System.out.println("CPU's Win Percentage- " + cpuWinPercentage
                    + "%");
            System.out.println("Number of Losses by CPU- " + mCpuLossCount);
            System.out.println("CPU's Loss Percentage- " + cpuLossPercentage
                    + "%");
        }
    }
}

---

愉快的编码。

我将展示一段经过重构的代码，向您展示处理输入和主循环的另一种方法

此代码对输入使用显式检查，在确保输入为小写后，在输入上使用

开关

。请注意，检查正确的用户输入应该放在游戏逻辑之外。你的游戏逻辑应该是：执行游戏的代码。如果你有两个CPU播放器呢

除此之外，它还包含许多编码提示，首先是注释：

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

class RockPaperScissors {
    // NOTE: prefer integers instead of doubles for counts
    private static int mUserWinCount = 0;
    private static int mCpuWinCount = 0;
    // NOTE: avoid double state
    // isn't user loss always identical to cpu win count?
    private static int mUserLossCount = 0;
    private static int mCpuLossCount = 0;
    private static int mDrawCount = 0;
    private static int mGameCount = 0;

    public static void main(String[] args) {

        // NOTE: always manage your resources
        try (Scanner scanner = new Scanner(System.in)) {

            // NOTE: never use recursion unless you cannot avoid it
            // prefer while loop over calling main)
            while (true) {
                String userInput = userInput(scanner);
                if (userInput.equals("-1")) {
                    score();
                    // NOTE: prefer running out of main over calling exit
                    break;
                }

                // NOTE: bring back the amount of state ASAP!
                // just lowercase has less state, enums have even less
                if (!validChoice(userInput)) {
                    System.out.println("Not a valid choice!");
                    continue;
                }

                try {
                    String cpuInput = cpuInput();
                    gameLogic(cpuInput, userInput);
                } catch (IllegalArgumentException iae) {
                    System.out.println(iae.getMessage());
                }
            }
        }
    }

    // NOTE: use explicit checks for user input
    static boolean validChoice(String userChoice) {
        switch (userChoice.toLowerCase()) {
        case "paper":
        case "scissors":
        case "rock":
            return true;
        default:
            return false;
        }
    }

    static String cpuInput() {
        // NOTE: only define your variables in the scope where they are needed
        // this doesn't need to be a field
        String mCpuInput;

        // NOTE: prefer new SecureRandom() over Random if performance is not
        // essential
        Random random = new Random(System.currentTimeMillis());
        int RandomNumber = random.nextInt(3);
        if (RandomNumber == 0)
            mCpuInput = "Rock";
        else if (RandomNumber == 1)
            mCpuInput = "Paper";
        else
            mCpuInput = "Scissors";

        return mCpuInput;
    }

    static String userInput(Scanner scanner) {
        String mUserInput;
        System.out
                .println("Enter Rock, Paper or Scissors, enter -1 in order to exit:- ");
        mUserInput = scanner.next();
        return mUserInput;

    }

    static void gameLogic(String cpuInput, String userInput) {
        // NOTE: use logging instead for debug statements
        System.out.println("CPU entered " + cpuInput + ", User entered "
                + userInput);

        // NOTE: learn to detect code smell...
        // if you don't really need args you should not have to define it
        // String [] args = new String[0];

        if (userInput.equalsIgnoreCase(cpuInput)) {
            // NOTE: don't mix input/output with the actual game rules
            // return the outcome and then print instead (not fixed)
            System.out.println("It's a draw!");
            mDrawCount++;
            mGameCount++;
        }

        if (userInput.equalsIgnoreCase("Rock")
                && cpuInput.equalsIgnoreCase("Scissors")
                || userInput.equalsIgnoreCase("Paper")
                && cpuInput.equalsIgnoreCase("Rock")
                || userInput.equalsIgnoreCase("Scissors")
                && cpuInput.equalsIgnoreCase("Paper")) {
            System.out.println("User wins!");
            mUserWinCount++;
            mCpuLossCount++;
            mGameCount++;
        }
        if (cpuInput.equalsIgnoreCase("Rock")
                && userInput.equalsIgnoreCase("Scissors")
                || cpuInput.equalsIgnoreCase("Paper")
                && userInput.equalsIgnoreCase("Rock")
                || cpuInput.equalsIgnoreCase("Scissors")
                && userInput.equalsIgnoreCase("Paper")) {
            System.out.println("CPU wins!");
            mCpuWinCount++;
            mUserLossCount++;
            mGameCount++;
        }

        // NOTE: avoid recursion
        // don't do this, if you do *document*
        // main(args);
    }

    static void score() {
        if (mGameCount == 0) {
            System.out.println("No games have been played..");
        } else {
            double userWinPercentage = (mUserWinCount / mGameCount) * 100;
            double userLossPercentage = (mUserLossCount / mGameCount) * 100;
            double cpuWinPercentage = (mCpuWinCount / mGameCount) * 100;
            double cpuLossPercentage = (mCpuLossCount / mGameCount) * 100;
            double drawPercentage = (mDrawCount / mGameCount) * 100;

            // NOTE: learn about printf when the time comes
            System.out.println("Number of Games Played- " + mGameCount);

            System.out.println("Number of Draws- " + mDrawCount);
            System.out.println("Percentage of Draws " + drawPercentage + "%");

            System.out.println("Number of Wins by User- " + mUserWinCount);
            System.out.println("User's Win Percentage- " + userWinPercentage
                    + "%");
            System.out.println("Number of Losses by User- " + mCpuLossCount);
            System.out.println("User's Loss Percentage- " + userLossPercentage
                    + "%");

            System.out.println("Number of Wins by CPU- " + mCpuWinCount);
            System.out.println("CPU's Win Percentage- " + cpuWinPercentage
                    + "%");
            System.out.println("Number of Losses by CPU- " + mCpuLossCount);
            System.out.println("CPU's Loss Percentage- " + cpuLossPercentage
                    + "%");
        }
    }
}

---

快乐编码。

如果输入部分不正确，我如何重复输入部分？非常感谢您的帮助。@ShumsBadwal-这是一个完全不同的问题。每个帖子设计一个特定的问题。一旦你成功了，我建议你发布它，并寻求帮助改进代码结构。@ShumsBadwal我在回答中创建了一些类似于评论的东西；它重复输入（提示：您应该重新使用扫描仪）。如果输入部分不正确，我如何重复输入部分？非常感谢您的帮助。@ShumsBadwal-这是一个完全不同的问题。每个帖子设计一个特定的问题。一旦你成功了，我建议你发布它，并寻求帮助改进代码结构。@ShumsBadwal我在回答中创建了一些类似于评论的东西；它会重复输入（提示：您应该重用扫描仪）。我还没有修复所有问题，我明确没有涉及到类、公共/私有等问题。因为您可能还没有读到这一章。好吧，我只需要一个CPU和一个用户，我在编写此代码时处于半睡眠状态，所以我对这一部分非常轻率，但无论如何，还是要感谢@Maarten Bodewsno，这不是问题，但要注意，你在半睡半醒时产生的代码可能会再次困扰你。一个星期五一次花了我一个星期一和一个星期二的时间来修复，重新开始会更容易更好。我还没有修复所有问题，我明确没有涉及到类、公共/私有等方面的问题，因为你可能还不在那一章。嗯，我只需要一个CPU和一个用户，我写这段代码时半睡半醒，所以我对这段代码很轻率，但无论如何感谢@Maarten Bodewsno没有问题，但请注意，你在半睡半醒时生成的代码可能会再次困扰你。一个星期五曾经花了我一个星期一和一个星期二的时间来修复，重新开始会更容易更好。下面的答案有帮助吗？如果是，请考虑使用复选标记。这向更广泛的社区表明，这是一个有帮助的答案，并给回答者和你自己带来了一些声誉。下面的答案有帮助吗？如果是，请考虑使用支票损坏。