Java老虎机代码拆分两类遇问题：Reel类spin方法调用异常求助

我完成了一个简易老虎机的Java代码，但对类的使用有疑惑。计划将随机生成符号的逻辑放到名为Reel的类的spin()方法中，但拆分后调用该方法时出现异常。以下是原代码及拆分后的代码，求指导正确的拆分方式。

原代码 #

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

public class LabProgram {

   public static void main(String[] args) {
      Scanner scnr = new Scanner(System.in);
   
      final int numReels = 3; //Declare how many reels spin on machine
      Random random = new Random(); // Create Random

      int[ ] symbols = new int[numReels]; // Create an array of three random numbers
      String[ ] logo = new String[numReels]; // Second Array to assign numbers to symbols
      final String[] allSymbols = {"Cherry", "7", "Grape", "Orange", "Lemon", "Spade", "Club", "Diamond", "Heart", "Ace"}; // A final list of what symbols there are
      
      
      for (int i = 0; i < symbols.length; ++i) { // Loop through the integer list to obtain random numbers
         symbols[ i ] = random.nextInt(10); //Random numbers from 0 - 9
      //System.out.println(symbols[i]); Test to make sure list is looping properly
      }
      for (int i = 0; i < symbols.length; ++i) { // Assign second array to the correct symbol according to number
         logo[i] = allSymbols[symbols[i]];
}
         
      
   //Test each element in list to make sure obtaining correct values
//System.out.println("symbol #: " + symbols[0] + " logo: " + logo[0]);
//System.out.println("symbol #: " + symbols[1] + " logo: " + logo[1]);
//System.out.println("symbol #: " + symbols[2] + " logo: " + logo[2]);
   
   // Simplify each element by assigning to single letter variables
   int a = symbols[0];
   int b = symbols[1];
   int c = symbols[2];
   
   String answer = "Y"; // Variable to be used in while loop (continue playing or not)
   int userBet; // Variable for amount user bets
   int doub; //Variable for reward when user matches two symbols
   int trip; //Variable for reward when user matches three symbols
   int jack; //Variable for reward when user matches three jackpot symbols
   int amountWon = 0;
   
   System.out.println("Welcome to the Simple Slot Machine! Enter a betting amount to spin!!"); // Print intro to user
   
   do { //do-while loop for when answer variable is Y or y
   userBet = scnr.nextInt(); // Take input for betting amount
   if (userBet < 10) { // Bet must be higher than $10
    System.out.println("Bet must be higher then $10");
   }
   
   if (a != b && a != c && b != c) { // When no symbols match the user loses amount that was bet
      System.out.println("You lost your $" + userBet);
      amountWon -= userBet;
   }
   else if (a == 1 && b == 1 && c == 1) { // When all jackpot symbols match user wins Jackpot and adds to winnings
    jack = userBet * 100;
    System.out.println("Congratulations! You have won with a " + logo[0] + ", " + logo[1] + ", " + logo[2] + " the jackpot of $" + jack);
    amountWon += jack;
   }
   else if (a == b && b == c) { // When three symbols match user wins triple award and adds to winnings
    trip = userBet * 70;
    System.out.println("Congratulations, you have won with a Triple!" + logo[0] + ", " + logo[1] + ", " + logo[2] + " $" + trip); 
    amountWon += trip;
   }
   else if (a == b || a == c || b == c) { // When two symbols match user wins award and add to winnings
    doub = userBet * 30;
    System.out.println("Congratulations, you have won with a Double!" + logo[0] + ", " + logo[1] + ", " + logo[2] + " $" + doub);
    amountWon += doub;
   }
   System.out.println("Continue? Y/N "); // Once awards accounted for ask if player continues or not
   answer = scnr.next();
} while (answer.equals("y") || answer.equals("Y"));
  if (!answer.equals("Y")) {
     if (amountWon < 0) { //Print statement for when player is in the hold
      System.out.println("You ended losing " + amountWon +" dollars" + ", but people always stop before they hit it big!");   
     }
     else { // Print statement for when player is in positive
    System.out.println("You ended with $" + amountWon + " come back again!"); 
     }
   }
  
   }
      
   }

拆分后代码 #

import java.util.Random;
import java.util.Arrays;

public class Reel {
   
   public void spin() {
   final int numReels = 3; //Declare how many reels spin on machine
      Random random = new Random(); // Create Random

      int[ ] symbols = new int[numReels]; // Create an array of three random numbers
      String[ ] logo = new String[numReels]; // Second Array to assign numbers to symbols
      final String[] allSymbols = {"Cherry", "7", "Grape", "Orange", "Lemon", "Spade", "Club", "Diamond", "Heart", "Ace"}; // A final list of what symbols there are
      
      
      for (int i = 0; i < symbols.length; ++i) { // Loop through the integer list to obtain random numbers
         symbols[ i ] = random.nextInt(10); //Random numbers from 0 - 9
      //System.out.println(symbols[i]); Test to make sure list is looping properly
      }
      for (int i = 0; i < symbols.length; ++i) { // Assign second array to the correct symbol according to number
         logo[i] = allSymbols[symbols[i]];
}
}
   
}

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

public class LabProgram {


   public static void main(String[] args) {
      Scanner scnr = new Scanner(System.in);
   Reel action = new Reel();
         
   action.spin();   
   //Test each element in list to make sure obtaining correct values
//System.out.println("symbol #: " + symbols[0] + " logo: " + logo[0]);
//System.out.println("symbol #: " + symbols[1] + " logo: " + logo[1]);
//System.out.println("symbol #: " + symbols[2] + " logo: " + logo[2]);
   
   // Simplify each element by assigning to single letter variables
   int a = symbols[0];
   int b = symbols[1];
   int c = symbols[2];
   
   String answer = "Y"; // Variable to be used in while loop (continue playing or not)
   int userBet; // Variable for amount user bets
   int doub; //Variable for reward when user matches two symbols
   int trip; //Variable for reward when user matches three symbols
   int jack; //Variable for reward when user matches three jackpot symbols
   int amountWon = 0;
   
   System.out.println("Welcome to the Simple Slot Machine! Enter a betting amount to spin!!"); // Print intro to user
   
   do { //do-while loop for when answer variable is Y or y
   userBet = scnr.nextInt(); // Take input for betting amount
   if (userBet < 10) { // Bet must be higher than $10
    System.out.println("Bet must be higher then $10");
   }
   
   if (a != b && a != c && b != c) { // When no symbols match the user loses amount that was bet
      System.out.println("You lost your $" + userBet);
      amountWon -= userBet;
   }
   else if (a == 1 && b == 1 && c == 1) { // When all jackpot symbols match user wins Jackpot and adds to winnings
    jack = userBet * 100;
    System.out.println("Congratulations! You have won with a " + logo[0] + ", " + logo[1] + ", " + logo[2] + " the jackpot of $" + jack);
    amountWon += jack;
   }
   else if (a == b && b == c) { // When three symbols match user wins triple award and adds to winnings
    trip = userBet * 70;
    System.out.println("Congratulations, you have won with a Triple!" + logo[0] + ", " + logo[1] + ", " + logo[2] + " $" + trip); 
    amountWon += trip;
   }
   else if (a == b || a == c || b == c) { // When two symbols match user wins award and add to winnings
    doub = userBet * 30;
    System.out.println("Congratulations, you have won with a Double!" + logo[0] + ", " + logo[1] + ", " + logo[2] + " $" + doub);
    amountWon += doub;
   }
   System.out.println("Continue? Y/N "); // Once awards accounted for ask if player continues or not
   answer = scnr.next();
} while (answer.equals("y") || answer.equals("Y"));
  if (!answer.equals("Y")) {
     if (amountWon < 0) { //Print statement for when player is in the hold
      System.out.println("You ended losing " + amountWon +" dollars" + ", but people always stop before they hit it big!");   
     }
     else { // Print statement for when player is in positive
    System.out.println("You ended with $" + amountWon + " come back again!"); 
     }
   }
  
   }
      
   }

问题分析 #

拆分后的代码存在两个核心问题：

1. 变量作用域问题：Reel类的spin()方法中，symbols和logo是局部变量，LabProgram类无法直接访问这些变量，这会导致编译错误。
2. 逻辑错误：原代码中只在程序启动时调用了一次spin()，后续循环中没有重新生成新的符号，导致每次游戏都是同一组结果，不符合老虎机的逻辑。

正确的拆分方案 #

修改Reel类，将symbols和logo设为实例变量，并提供getter方法供外部访问；同时在LabProgram的循环内每次用户下注后重新调用spin()生成新结果。

修改后的Reel类 #

import java.util.Random;

public class Reel {
    private final int numReels = 3;
    private final String[] allSymbols = {"Cherry", "7", "Grape", "Orange", "Lemon", "Spade", "Club", "Diamond", "Heart", "Ace"};
    private int[] symbols;
    private String[] logo;
    private Random random;

    public Reel() {
        random = new Random();
        symbols = new int[numReels];
        logo = new String[numReels];
    }

    public void spin() {
        // 生成随机符号编号
        for (int i = 0; i < symbols.length; ++i) {
            symbols[i] = random.nextInt(10);
        }
        // 映射为符号名称
        for (int i = 0; i < logo.length; ++i) {
            logo[i] = allSymbols[symbols[i]];
        }
    }

    // Getter方法供外部获取结果
    public int[] getSymbols() {
        return symbols;
    }

    public String[] getLogo() {
        return logo;
    }
}

修改后的LabProgram类 #

import java.util.Scanner;

public class LabProgram {
    public static void main(String[] args) {
        Scanner scnr = new Scanner(System.in);
        Reel action = new Reel();

        String answer = "Y";
        int userBet;
        int amountWon = 0;

        System.out.println("Welcome to the Simple Slot Machine! Enter a betting amount to spin!!");

        do {
            userBet = scnr.nextInt();
            if (userBet < 10) {
                System.out.println("Bet must be higher than $10");
                continue; // 跳过本次循环，重新要求下注
            }

            // 每次下注后重新转动老虎机
            action.spin();
            int[] symbols = action.getSymbols();
            String[] logo = action.getLogo();
            int a = symbols[0];
            int b = symbols[1];
            int c = symbols[2];

            // 判断中奖结果
            if (a != b && a != c && b != c) {
                System.out.println("You lost your $" + userBet);
                amountWon -= userBet;
            } else if (a == 1 && b == 1 && c == 1) {
                int jack = userBet * 100;
                System.out.printf("Congratulations! You have won with a %s, %s, %s the jackpot of $%d%n", logo[0], logo[1], logo[2], jack);
                amountWon += jack;
            } else if (a == b && b == c) {
                int trip = userBet * 70;
                System.out.printf("Congratulations, you have won with a Triple! %s, %s, %s $%d%n", logo[0], logo[1], logo[2], trip);
                amountWon += trip;
            } else if (a == b || a == c || b == c) {
                int doub = userBet * 30;
                System.out.printf("Congratulations, you have won with a Double! %s, %s, %s $%d%n", logo[0], logo[1], logo[2], doub);
                amountWon += doub;
            }

            System.out.println("Continue? Y/N ");
            answer = scnr.next();
        } while (answer.equalsIgnoreCase("Y"));

        if (amountWon < 0) {
            System.out.printf("You ended up losing %d dollars, but people always stop before they hit it big!%n", -amountWon);
        } else {
            System.out.printf("You ended with $%d come back again!%n", amountWon);
        }

        scnr.close();
    }
}

关键改进点 #

• 将Reel类的核心数据（symbols、logo）设为实例变量，通过getter方法暴露，解决作用域问题。
• 在每次用户下注后调用spin()，确保每次游戏结果都是随机的。
• 修复了原代码中下注金额检查后未跳过后续逻辑的问题，避免无效下注仍执行中奖判断。
• 使用equalsIgnoreCase()简化继续游戏的判断逻辑，同时关闭Scanner资源，规范代码。

内容的提问来源于stack exchange，提问作者EliKhan