将值从子类存储到父类

Question

我想知道如何将值从子类存储到父类。

public class Question {
private HashMap<String,ArrayList<String>> mcqHashMap = new HashMap<String,ArrayList<String>>(); //storing question and options of MCQ
public ArrayList<String> rankingquestion = new ArrayList<String>();
public Scanner scan = new Scanner(System.in);
public ArrayList<String> correctMCQAnswer = new ArrayList<String>(); // will keeps the correct answer of each question
HashMap<String,ArrayList<String>> newmcqHashMap;
public HashMap<String, ArrayList<String>> getMCQQuestionAnswer() {
    System.out.println("NEW:" + mcqHashMap);
    return this.newmcqHashMap;
}
public void setMCQQuestionAnswer(HashMap<String, ArrayList<String>> mcqQuestionAnswer) {
    this.mcqHashMap = mcqQuestionAnswer;
    System.out.println("After setting" + this.mcqHashMap);
    newmcqHashMap = this.mcqHashMap;
}

}

public class MultipleChoiceQuestion extends Question {
String storeMultipleChoiceQuestion;
ArrayList<String> answersMCQ = new ArrayList<String>();
HashMap<String, ArrayList<String>> mcqQuestionAnswer = new HashMap<String, ArrayList<String>>();

//returns MCQQuestion
public String storeMultipleChoiceQuestion() {
    System.out.println("Enter the Multiple question: ");
    String MultipleChoiceQuestion = scan.nextLine();
    while(MultipleChoiceQuestion.isEmpty()) {
        System.out.println("Null in invalid");
        MultipleChoiceQuestion = scan.nextLine();   
    }
    return MultipleChoiceQuestion;
}
//creates MCQ Questions with mcq options
public void create() {
    String value = storeMultipleChoiceQuestion();
    try {
        System.out.println("Enter the number of choices for your multiple choice question:");
        int numberOfChoices = scan.nextInt();
        scan.nextLine();
        if(numberOfChoices <= 0) {
            System.out.println("Must be greater than 0");
        }
        else {
            for(int i=1; i <= numberOfChoices; i++){
                System.out.println("Enter prompt " + i);
                String Option = scan.nextLine();
                answersMCQ.add(Option);
                while(Option.isEmpty()) {
                    System.out.println("Null in invalid");
                     Option = scan.nextLine();
                }
                mcqQuestionAnswer.put(value, answersMCQ);
                super.setMCQQuestionAnswer(mcqQuestionAnswer);
                //this.mcqHashMap.put(value, answersMCQ);                   
            }
        }
        }catch (Exception e) {
        System.out.println("Exception thrown! Use integer greater than 0.");
        }
        }

到这里它很好...

现在，当我尝试从另一个子类访问调查时。

public class Survey extends Question implements Serializable {

MultipleChoiceQuestion mcq = new MultipleChoiceQuestion();
public void Display() {
    System.out.println("THis is from get " + this.getMCQQuestionAnswer());
    System.out.println("THis is from get mcqhash" + this.newmcqHashMap);
}

'不打印任何内容...

我确定我在某处做错了。我也在家长班中使用了getter setter，但仍然没有运气。所以基本上，问题将存储到 mcqHashMap 中，我想使用存储的 mcqHashMap 来显示调查类的目的。

感谢帮助。谢谢

Answer 1

没

关系，伙计们，我想通了。谢谢！我做了受保护的静态而不是受保护的哈希图。不好的做法，但有效！

感谢您的帮助。