java - 如何让 FillInTheBlank 打印问题(继承)

Question

这个问题已经有答案了:

What is a StackOverflowError? (15 个回答)

已关闭 3 年前。

我是继承新手，在完成作业时遇到问题。我的错误是收到堆栈溢出错误。

作业由类层次结构组成，用于打印测试和答案键，每个不同的类是不同类型的问题。我的程序可以打印对象问题，但不能打印填空问题

任何帮助或指出正确的方向将不胜感激。

驱动程序.java

package assignment9testpapers;

public class Driver {
    public static void main(String[] args) {
        Test trial = new Test( 3, 3);
        ObjectiveQuestion obj = new ObjectiveQuestion( 3,  2,  1, "what is 1 + 1",  "2");
        trial.addObjectiveQuestion(obj);
        ObjectiveQuestion fitbl = new FillInTheBlankQuestion(3 ,2 ,1 , "Who is the professor of 1068", "John Fiore");
        trial.addFillInTheBlankQuestion(fitbl);
        trial.printTest();
        trial.printTestAnswers();
    }
}

问题.java

1 package assignment9testpapers;
2
3 public class Question {
4   private int points;
5   private int difficulty;
6   private int answerSpace;
7   private String questionText;
8   
9   public final int MIN_DIFFICULTY = 1;
10  public final int MAX_DIFFICULTY = 5;
11
12  public Question(int points, int difficulty, int answerSpace, String 
 questionText) {
13      this.points = points;
14  this.answerSpace = answerSpace;
15      this.questionText = questionText;
16      
17      if(difficulty>=MIN_DIFFICULTY && difficulty <= MAX_DIFFICULTY) {
18          this.difficulty=difficulty;
19      }else if(difficulty<MIN_DIFFICULTY) {
20          this.difficulty=MIN_DIFFICULTY;
21      } else {
22          this.difficulty=MAX_DIFFICULTY;
23      }
24  }
25  
26  public String toString(){
27      return "Points" + points+ "difficulty" + difficulty +"question" + questionText;
28  }
29  
30  public String getQuestionText() {
31      return questionText+makeAnswerSpace();
32  }
33  
34  public int getPoints() {
35      return points;
36  }
37  
38  private String makeAnswerSpace() {
39      String space="";
40      for(int i = 0; i<answerSpace; i++) {
41          space+='\n';
42      }
43      return space;
44  }

ObjectiveQuestion.java

package assignment9testpapers;

public class ObjectiveQuestion extends Question {
    private String correctAnswer;

    public ObjectiveQuestion(int points,int difficulty, int answerSpace, String questionText, String correctAnswer ) {
        super(points, difficulty, answerSpace, questionText);
        this.correctAnswer=correctAnswer;
    }

    public String getCorrectAnswer() {
        return correctAnswer;
    }


}

测试.java

package assignment9testpapers;

public class Test {
    private String[] questions;
    private String[] answer;
    private int totalPoints;

    private int questionCount = 0;

    public Test(int numQuestions, int totalPoints) {
        this.questions = new String[numQuestions];
        this.answer = new String[numQuestions];
        this.totalPoints=totalPoints;
    }

    public void addObjectiveQuestion(ObjectiveQuestion q) {
        questions[questionCount] = q.getQuestionText();
        answer[questionCount]=q.getCorrectAnswer();
        questionCount++;
    }

    public void addMultipleChoiceQuestion(MultipleChoiceQuestion q) {
        questions[questionCount] = q.getQuestionText();
        answer[questionCount]=q.getCorrectAnswer();
        questionCount++;
    }

    public void addFillInTheBlankQuestion(ObjectiveQuestion q) {
        questions[questionCount] = q.getQuestionText();
        answer[questionCount]=q.getCorrectAnswer();
        questionCount++;
    } 




    public void printTest() {
        for (int i = 0; i<questions.length; i++) {
            System.out.println(questions[i]);
        }
    }

    public void printTestAnswers() {
        for (int i = 0; i<answer.length; i++) {
            System.out.println(answer[i]);
        }
    }   
}

FillInTheBlankQuestion.java

package assignment9testpapers;

public class FillInTheBlankQuestion extends ObjectiveQuestion{

    public FillInTheBlankQuestion(int points,int difficulty, int answerSpace, String questionText, String correctAnswer ) {
        super(points, difficulty, answerSpace, questionText, correctAnswer);
    }

    public String getQuestionText() {
        return "______________" + getQuestionText();
    }
    public String getCorrectAnswer() {
        return "______" + getQuestionText() + getCorrectAnswer();
    }


}

错误信息:

Exception in thread "main" java.lang.StackOverflowError
    at java.base/java.lang.StringBuilder.<init>(StringBuilder.java:124)
    at assignment9testpapers.FillInTheBlankQuestion.getQuestionText(FillInTheBlankQuestion.java:10)

Answer 1

在“public class FillInTheBlankQuestion”方法“public String getQuestionText() 中，您正在调用其自身内部的方法，导致无限循环。如果您尝试使用父类(super class)中的方法，请使用 super.getQuestionText()。