无法从相关类调用必需的方法

Question

我有一个任务，在那里我需要为“TotalCompetities”创建一个程序，它由多个“Competition”组成。我需要创建一个应用程序，允许用户做各种选项，与TotalCompetition相关。

如果选择了第一个选项（“创建一个新的竞争”），通过键入“1”然后按Enter，程序应该调用TotalCompetities类的addNewCompetition方法以添加一个具有给定名称的新竞争。创建新的比赛后，程序应该回到主菜单。

此刻，这是我的代码：

public class TotalCompetitions {
    private ArrayList<Competition> competitions;

    
    public TotalCompetitions() {
        this.competitions = new ArrayList<Competition>();

    }

    public ArrayList<Competition> getCompetitions() {
        return competitions;
    }

    public void setCompetitions(ArrayList<Competition> competitions) {
        this.competitions = competitions;
    }

    
    public Competition addNewCompetition(String name, int id) {
        Competition newCompetition = new Competition(name, id);
        return newCompetition;
    }
}

  public static void main(String[] args) {
        Scanner keyboard = new Scanner(System.in);
        TotalCompetitions sc = new TotalCompetitions();
        int competitionId = 0;

        while (true) {
            System.out.println("Please select an option. Type 5 to exit.");
            System.out.println("1. Create a new competition");
            System.out.println("2. Add new entries");
            System.out.println("3. Draw winners");
            System.out.println("4. Get a summary report");
            System.out.println("5. Exit");
            
            String command = keyboard.next();
            
            
            if (command.equals("1")) {
                    keyboard.nextLine();
                    System.out.println("Competition name:");
                    String name = keyboard.nextLine();
                    competitionId += 1;
                    sc.addNewCompetition(name, competitionId);
                    System.out.println("A new competition has been created!");
                    System.out.println("Competition ID: " + competitionId + ", Competition Name: " + name);
            }
            else if (command.equals("2")) {
                    sc.addEntry();
            }
            else if (command.equals("5")) {
                    System.out.println("The end");
                    break;
            }
}

Answer 1

sc.addNewCompetition（name,competitionId）；返回类型为Competition的新对象，但是，您的程序不使用此新对象。变量sc仍然属于totalcompetity类型，该类型与competity不相关。此外，您的方法addNewCompetition（String id,int id)不会将新对象添加到ArrayList中。解决方案是存储sc.AddNewCompetity(...)调用返回的对象，并在此对象上调用AddEntry()。