Question

我想将这些方法放入ArrayList中，但我无法弄清楚如何做到这一点。我正在使用NetBeans，该程序将成为一个GUI。

这是我的代码：

public class canada150Tour extends javax.swing.JFrame {

    ArrayList <String> mcQuestions = new ArrayList(); //This is the array I want to put the below methods into.


    private void questionFredricton(){
        outputTextQuestion.append("Where is Fredricton located?");

        displayQuestions.append("New Brunswick");        
    }
    private void questionRegina(){
        outputTextQuestion.setText("Where is Regina located?");

        displayQuestions.append("Saskatchewan");

    }
    private void questionOttawa(){
        outputTextQuestion.setText("Where is Ottawa located?");

        displayQuestions.append("Ontario");
    }
    private void questionHalifax(){
        outputTextQuestion.setText("Where is Halifax located?");

        displayQuestions.append("Nova Scotia");
    }
    private void questionQuebecCity(){
        outputTextQuestion.setText("Where is Quebec City located?");

        displayQuestions.append("Quebec");
    }
    private void questionEdmonton(){
        outputTextQuestion.setText("Where is Edmonton located?");

        displayQuestions.append("Alberta");
    }
    private void questionCharlottetown(){
        outputTextQuestion.setText("Where is Charlottetown located?");

        displayQuestions.append("Prince Edward Island");
    }
    private void questionVictoria(){
        outputTextQuestion.setText("Where is Victoria located?");

        displayQuestions.append("British Columbia");
    }
    private void questionIqaluit(){
        outputTextQuestion.setText("Where is Iqaluit located?");

        displayQuestions.append("Nunavut");
    }
    private void questionWhitehorse(){
        //outputTextQuestion.setText("Where is Whitehorse located?");

        displayQuestions.append("Yukon");
    }
    private void questionWinnipeg(){
        outputTextQuestion.setText("Where is Winnipeg located?");

        displayQuestions.append("Manitoba");
    }

我试过了：

Collections.addAll(mcQuestions, questionFredricton(), questionRegina());

等等所有方法，但显然不起作用。

当我尝试添加到ArrayList（上面）时出现编译错误：

这里不允许
'void'类型

我对Java很新，所以还在学习。

修改这最终将是一个多项选择测验。我基本上想把方法放到一个数组中，这样我就可以随机选择方法。

提前致谢！

Answer 1

您需要将ArrayList作为参数传递给方法，以便在其中添加元素，例如：

private void questionFredricton(ArrayList <String> mcQuestions){
    mcQuestions.add("Where is Fredricton located?");
}

并调用这样的方法：

ArrayList <String> mcQuestions = new ArrayList();
questionFredricton(mcQuestions);

此外，您似乎需要在此处存储这对问题和答案，在这种情况下，最好使用HashMap，例如：

private void questionFredricton(Map<String, String> questions){
    questions.put("Where is Fredricton located?", "New Brunswick");
}

并称之为：

Map<String, String> questions = new HashMap<>();
questionFredricton(questions);

这样，您就可以存储问题和答案。 questions.keySet()会为您提供所有问题的清单，questions.get("<questions>")会给您答案。

Answer 2

如果要在String String ArrayList中添加String，您的方法应返回QuestionAndResponse。但实际上我认为你不应该这样做，因为你需要问题和回答。拥有List而不是两个QuestionAndResponse字符串的列表似乎更好 public class QuestionAndResponse{ public QuestionAndResponse(String question, String response){ this.question = question; this.response = response; } // getters for fields }可以包含问题的文本，但也可以包含预期响应的文本。

List <QuestionAndResponse> mcQuestionsResponses = new ArrayList<>();

所以你可以声明List：

private void questionFredricton(){
    outputTextQuestion.append("Where is Fredricton located?");
    displayQuestions.append("New Brunswick");        
}

你可以替换它：

private QuestionAndResponse questionFredricton(){
    return new QuestionAndResponse("Where is Fredricton located?","New Brunswick");
}

由：

public class Canada150Tour extends JFrame {
    List <QuestionAndResponse> mcQuestionsResponses;
       ...
    public Canada150Tour(){
         mcQuestionsResponses = new ArrayList<>(); 
         mcQuestionsResponses.add(questionFredricton());
    }

     private QuestionAndResponse questionFredricton(){
        return new QuestionAndResponse("Where is Fredricton located?",
                                        "New Brunswick");
     }
}

现在您可以使用Canada150Tour（请注意遵循命名约定的第一个字母的大写）构造函数：

seaborn.set(style="white", context="talk")
a = pandas.DataFrame.from_dict({'Attendees': {pandas.Timestamp('2016-12-01'): 10,
  pandas.Timestamp('2017-01-01'): 12,
  pandas.Timestamp('2017-02-01'): 15,
  pandas.Timestamp('2017-03-01'): 16,
  pandas.Timestamp('2017-04-01'): 20}})
ax = seaborn.barplot(data=a, x=a.index, y=a.Attendees, color='lightblue', )
seaborn.despine(offset=10, trim=False)
ax.set_ylabel("")
ax.set_xticklabels(['Dec', 'Jan','Feb','Mar','Apr'])
plt.show()

将方法放入ArrayList Java中

2 个答案: