Hangman游戏报错Index 0 out of bounds for length 0求助

错误根源 #

报错触发在CharacterSearch()方法的key.charAt(0)调用，核心问题是：

• 使用input.nextInt()选择菜单后，输入缓冲区残留了换行符
• 后续首次调用input.nextLine()时，会直接读取到这个空换行符，导致choice1成为空字符串
• 空字符串调用charAt(0)必然触发索引越界异常

修复步骤 #

1. 清除换行符残留：在choice = input.nextInt();后添加input.nextLine();，消耗缓冲区里的换行符，确保后续nextLine()能正确读取用户输入的字母。
2. 添加输入校验：读取用户猜测的字母后，检查输入是否为空或长度大于1，避免无效输入引发异常。
3. 细节优化：把字符串拼接改为StringBuilder提升效率，错误次数输出时根据数量自动调整单复数语法。

修复后的完整代码 #

package besingaPi_LE_3_2;

import java.util.Scanner;

public class GameHangman {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int miss = 0; 
        String choice1;
        String temp;
        
        String[] words = {"giraffe", "hipopotamus", "gorilla", "peacock", "armadillo"};

        int choice;
            mainMenu();
            choice = input.nextInt();
            input.nextLine(); // 清除nextInt()后的换行符
            System.out.println();
            if(choice == 1){
                
                String wordRandom = Randomizer(words);
                String mute  = secretWord(wordRandom);
                temp = mute;
                System.out.println(wordRandom);
                System.out.println("Note: use only small character/s");
                
                while(!mute.equals(wordRandom)) {
                    System.out.print("(Guess) Enter a letter in word " + mute + " > ");         
                    choice1 = input.nextLine().trim();
                    
                    // 校验输入有效性
                    if(choice1.isEmpty() || choice1.length() != 1) {
                        System.out.println("Please enter a single lowercase letter!");
                        continue;
                    }
                    
                    mute = CharacterSearch(wordRandom, mute, choice1);

                    if(temp.equals(mute)) {
                        miss++;
                    }
                    temp = mute;
    
                }
                System.out.println("The word is " + wordRandom + ". You missed " + miss + " time" + (miss !=1 ? "s" : "") + ".");
            }
            else if (choice == 0) {
                System.out.println("Thank you!!");
                return;
            }

    }
    public static void mainMenu() {
        System.out.println("Welcome to Hangman");  
        System.out.println("[1]START\n[0]EXIT"); 
        System.out.print("Please input your choice: ");
    }
    public static String CharacterSearch(String word, String muted, String key) {
        StringBuilder update = new StringBuilder(muted);
        for(int i = 0; i < word.length(); i++) {
            if(word.charAt(i)  == key.charAt(0)) {
                update.setCharAt(i,key.charAt(0));
            }
        }
        return update.toString();
    }
    public static String secretWord(String word) {
        StringBuilder temp = new StringBuilder();
        for(int i = 0; i < word.length(); i++) {
            temp.append("*");
        }
        return temp.toString();
    }
    
    public static String Randomizer(String[] words) {
        int rand = (int)(Math.random() * words.length);
        return words[rand];
    }
}

内容的提问来源于stack exchange，提问作者Piolo Pascual Besinga