Question

到目前为止，这是我的计划：

import java.util.Arrays;

public class HangmanWord {

    private String[] possibleWords = {"laptop", "college", "programing"};
    private String word;
    private char[] progress;
    private int wrongCount = 0;
public HangmanWord() {
    int randomPossibleWord = (int) (Math.random() * possibleWords.length-1);
  String word = possibleWords[randomPossibleWord];
  char[] progress = new char[word.length()];
  Arrays.fill(progress,'-');
  }
public void display() {
    System.out.print(progress);
    System.out.println();
}
public boolean guess(char c) {
    boolean matchFound = false;
    for (int i = 0; i < word.length(); i++ ) {
        if (word.charAt(i) == c ) {
            progress[i] = c;
            matchFound = true;
        }
    }
    return false;

}

public boolean isSolved() {
    for (int i = 0; i < progress.length; i++ ) {
        if(progress[i] == '-'){
            return false;
        }
    }
    return true;

}
public int getWrongCount() {
    return wrongCount;  
}
public String getWord() {
    return word;

}

}

public class Hangman {

    public static void main(String[] args) {
int MAX_INCORRECT = 5;
System.out.println("Welcome to Hangman.");
HangmanWord wordObj = new HangmanWord();
System.out.print("Here is your word: ");
wordObj.display();
    }

}

我的输出应该是这样的：

Welcome to Hangman.
Here is your word: ------

但是，我收到以下错误：

Welcome to Hangman.
Here is your word: Exception in thread "main" java.lang.NullPointerException
    at java.io.Writer.write(Writer.java:127)
    at java.io.PrintStream.write(PrintStream.java:503)
    at java.io.PrintStream.print(PrintStream.java:653)
    at HangmanWord.display(HangmanWord.java:16)
    at Hangman.main(Hangman.java:9)

Answer 1

您正在构造函数中重新定义变量单词和进度。您应该简单地使用它们而不将它们声明为新变量，因为它们已经定义。目前你在本地定义它们，构造函数工作但是使用那些本地定义的变量而不是你的对象的单词和进度变量，因此当你离开作用域并调用display（）它将使用你的对象的进度数组从未实际初始化过。

将其更改为以下内容，因此您不会重新定义变量字和进度，因此

public HangmanWord() {
    int randomPossibleWord = (int) (Math.random() * possibleWords.length-1);
    word = possibleWords[randomPossibleWord];
    progress = new char[word.length()];
    Arrays.fill(progress,'-');
}

刽子手游戏错误

1 个答案: