Java中charAt()方法的问题

Question

我正在尝试在Java中创建一个基于文本的刽子手。

这是我的Java代码:

package hangman;
import java.util.Random;
import java.util.Scanner;
import java.lang.String;
public class Hangman {
    public static void main(String[] args) {
        // TODO code application logic here
        Scanner chez = new Scanner(System.in);
        Scanner waffle = new Scanner(System.in);
        Random randomGenerator = new Random();
        StringBuilder displayWord = new StringBuilder("______________________________");
        String theWord = null;
        String preLetter;
        //String sbDisplayWord;
        char letter = 0;
        int randomNumber;
        int lengthOfWord;
        int numberOfLetterInWord = 0;
        int gDisplay;
        int guessWordNumber = 0;
        String guessWord;
        RandomWord troll = new RandomWord();    
        randomNumber = randomGenerator.nextInt(12);
        //Fill var with the word.
        theWord = troll.wordDecide(randomNumber);
        System.out.println ("Welcome to Hangman!");
        lengthOfWord=theWord.length( );
        System.out.println("This word has " + lengthOfWord + " letters.");
        System.out.println("You have 20 guesses.");
        for (int g =19; g >= 0; g--) {    
            System.out.println("If you want to guess the word, type 0. If you want to guess a letter, type 1.");
            guessWordNumber=chez.nextInt();
            if (guessWordNumber==0) {
                System.out.println("Enter the word now. Remember, don't capitalize it.");
                guessWord=waffle.nextLine();
                if (guessWord.equals(theWord)) {
                    System.out.println("YOU WIN");
                    System.exit(0);
                } else {
                    System.out.println("Sorry, this wasn't the correct word.");
                }
            } else if (guessWordNumber==1) {
                System.out.println("Please enter the letter you wish to guess with.");
                //System.out.println("It will tell you if you have guessed right for any of the letters. If it is blank, that means none of the letters match.");
                preLetter=chez.nextLine();
                letter=preLetter.charAt(0);
                System.out.println("");
                for(int i = 0; i <= lengthOfWord -1; i++ ) {     //-Eshan
                    if (letter == theWord.charAt( i )) {
                        numberOfLetterInWord=i+1;
                        System.out.println("This letter matches with letter number " + numberOfLetterInWord + " in the word.");
                        displayWord.setCharAt(i, letter);
                    } else {
                        numberOfLetterInWord=i+1;
                        System.out.println("This letter doesn't match with letter number " + numberOfLetterInWord + " in the word.");
                    }       

                }
                System.out.println("");
                System.out.println("The word so far is " + displayWord);
                System.out.println("");
                gDisplay = g + 1;
                System.out.println("You have " + gDisplay + " guesses left.");
            } else {
                System.exit(0);
            }
        }
        System.out.println("GAME OVER");
        System.exit(0);
    }
}

package hangman;
public class RandomWord {
    private static String[] wordArray = {
        "psychology",
        "keratin",
        "nostalgia",
        "pyromaniac",
        "chlorophyl",
        "derivative",
        "unitard",
        "pterodactyl",
        "xylophone",
        "excommunicate",
        "obituary",
        "infinitesimal",
        "concupiscent",
    };
    public String wordDecide(int randomNumber) {
        String theWord;
        theWord = wordArray[randomNumber];
        return theWord;
    }
}

Netbeans给我这个错误:

线程"main"异常java.lang.StringIndexOutOfBoundsException:字符串索引超出范围:0
java.lang.String.charAt (String.java: 695)
在hangman.Hangman.main (Hangman.java: 56)
Java Result: 1

Answer 1

当您在长度为0的字符串上调用charAt(0)时可能会发生这种情况。在调用该方法之前，应该检查字符串是否为空。

Answer 2

由于

一行，您将获得StringIndexOutOfBoundsException

guessWordNumber = chez.nextInt();

不使用换行符，并将该字符传递到

行。

preLetter = chez.nextLine();

不会阻塞，因为它已经接收了输入。这将一个空的String分配给preLetter，从而导致异常。你可以使用扫描器#nextLine来使用这个字符:

guessWordNumber = Integer.parseInt(chez.nextLine());