我的类应该是什么类型才能访问类及其扩展的类？
您有
public class Question
和
public class MultipleChoice extends Question
主要
public class SurveyQuestions
SurveyQuestions 有
private static List<Question> q = new ArrayList<Question>();
您不断添加问题以及问题组成的所有内容到列表中。
完成后，您想要迭代列表
for (Question q : SurveyQuestions.getInstance().getListOfQuestions())
Question：“q”应该是什么类型，以便它可以访问 Question 和 MultipleChoice？
you have
public class Question
and
public class MultipleChoice extends Question
and
public class SurveyQuestions
where SurveyQuestions has
private static List<Question> q = new ArrayList<Question>();
In main you keep adding questions and all the things questions are composed of to the list.
Once done, you want to iterate over the list
for (Question q : SurveyQuestions.getInstance().getListOfQuestions())
Question: What type should "q" be so that it has access to both Question and MultipleChoice?
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评论（2）
如果“访问”的意思是“访问...的方法”，则不能将其作为 MultipleChoice，因为有些问题可能并非如此。所以它必须是
Question，然后你可以通过if(q instanceof MultipleChoice)检查它是否是多项选择If by "access to" you mean "access to the methods of"- you can't have it as
MultipleChoicebecause some questions might not be such. So it has to beQuestion, and then you can check if it is a multiple-choice byif(q instanceof MultipleChoice)您应该将其设为
问题。您不能将
MultipleChoice作为一个普通的问题，不是一个MultipleChoice...而是一个MultipleChoice是一个问题。所以Question可以代表这两种类型。You should make it
Question.You can't make it
MultipleChoiceas a plainQuestionis not aMultipleChoice... but aMultipleChoiceis aQuestion. SoQuestioncan represent both types.