球队和球员反对 Java 困难

Question

基本上，我正在努力创建一个管理团队和球员的 Java 程序。

据我了解，我将拥有一个团队和一个球员课程。在 team 类中会有 get 和 set 方法，以及某种形式的集合来存储球员，比如数组列表？然后在播放器类中相关的get和set方法。

这种设置是因为一支球队有一对多的球员，对吧？

我在尝试让它工作时遇到了无穷无尽的麻烦。我遇到的一个特殊问题是，每次我创建一个团队对象并向其中添加一个球员对象时，然后创建另一个团队对象和另一个球员，但是如果我列出该新球队的球员，它会显示前一个球员添加到第一支球队和新球员。

所以我想它又回到了绘图板上，想知道是否有人可以就如何构建它提供一些一般性建议？

非常感谢，

import java.util.Iterator;

public class test {
public test() {
}

//Method to show the team and its players

public static void showTeamPlayers(Team aTeam) {
    Player players;
    System.out.println(aTeam.getTeamName());
    Iterator e = aTeam.getPlayerList().iterator();
    while (e.hasNext()) {
        players = (Player)e.next();
        System.out.println("\t" + players.getPlayerNumber() + " " + players.getPlayerName());
    }
    System.out.println("");
}

public static void main(String[] args) {
    int teamID;
    String teamName = "";

    //First create a divison/league
    League DivisionOne = new League("Division One");

    //Create a new team object
    Team team = new Team(teamName);

    //Asks the user to enter a team name and stores the input
    UserInput.print("Enter team name:");
    teamName = UserInput.readString();

    team.setTeamName(teamName);

    //Add the team
    DivisionOne.addTeam(new Team(teamName));

    Player player = new Player(0, "Dave");
    Player player1 = new Player(1, "Dennis");
    Player player2 = new Player(2, "Peter");

    //Add to team
    team.addPlayer(player);
    team.addPlayer(player1);
    team.addPlayer(player2);

    test.showTeamPlayers(team);

    //Asks the user to enter a team name and stores the input
    UserInput.print("Enter team name:");
    teamName = UserInput.readString();

    team.setTeamName(teamName);

    //Add the team
    DivisionOne.addTeam(new Team(teamName));

    Player player3 = new Player(3, "Creamer");
    Player player4 = new Player(4, "Matt");
    Player player5 = new Player(5, "John");

    //Add to team 1
    team.addPlayer(player3);
    team.addPlayer(player4);
    team.addPlayer(player5);

    test.showTeamPlayers(team);
}
}

Answer 1

您的结构应该完全正确（顺便说一句，“一对多关联”用“1:n”或“1:(1..n)”来描述）。

您的代码中的某处肯定有错误（发布它；）），例如静态字段或两次使用标识符，或者您可能会在此处遇到 ArrayList 问题（尝试使用 LinkedList 进行测试），但我不确定。

编辑： 你忘了发布你的模型，我们只看到了它的测试，但是你已经发现了一些错误：

Team team = new Team(teamName);
teamName = UserInput.readString();
team.setTeamName(teamName);

到目前为止，一切都很好。除了它没有意义，用空的teamName创建一个Team实例然后重置它，但是nvm....

DivisionOne.addTeam(new Team(teamName));

Babam，您没有将上面创建的 Team 实例添加到 DivisionOne，您正在创建一个新实例。其实就是Bug No.1

team.addPlayer(player);
team.addPlayer(player1);
team.addPlayer(player2);

但是您将新玩家放入您在上面创建的实例中，他们没有进入为 DivisionOne 创建的团队......如果你愿意的话，Bug No.2......然后

team.setTeamName(teamName);
DivisionOne.addTeam(new Team(teamName));
.
.
.
team.addPlayer(player3);
team.addPlayer(player4);
team.addPlayer(player5);

同样，您只是为您的第一个 Team 实例设置了一个新的 teamName，然后您正在为 DivisionOne 创建一个新的 Team。到目前为止，Bug No.3 ;) 但是您将一些新玩家放入“旧”团队实例中，与上述相同。

总而言之，您创建的“团队”实例与您的 DivisionOne 无关。因此，您创建了一个 Team 实例，将所有六个玩家放在一起，并在其上调用了 2 次 showTeamPlayers。毕竟前三名选手还在里面也就不足为奇了....

最后一点：

League DivisionOne = new League("Division One");

应该是

League divisionOne = new League("Division One");

由于变量从不以大写字母开头，“DivisionOne”也可以是静态类（因为类总是以大写字母开头...）

Answer 2

PaddyG 已经提到了错误。这是解决方案：

替换此代码：

teamName = UserInput.readString();

team.setTeamName(teamName);


//Add the team
DivisionOne.addTeam(new Team(teamName));

与：

teamName = UserInput.readString();

team = new Team(teamName);

//Add the team
DivisionOne.addTeam(team);

还有替换：

teamName = UserInput.readString();

team.setTeamName(teamName);

//Add the team
DivisionOne.addTeam(new Team(teamName));


Player player3 = new Player(3, "Creamer");
Player player4 = new Player(4, "Matt");
Player player5 = new Player(5, "John");

与：

teamName = UserInput.readString();

team = new Team(teamName);

//Add the team
DivisionOne.addTeam(team);


Player player3 = new Player(3, "Creamer");
Player player4 = new Player(4, "Matt");
Player player5 = new Player(5, "John");

正如您在上面的代码中看到的，我们使用新团队的新实例更新了 team 变量。并且这个新实例被添加到DivisionOne。当您执行DivisionOne.addTeam(new Team(teamName)); 时，您正在创建一个全新的实例并将其添加到 DivisionOne 但您要添加玩家的实例是不同的实例（由team 变量保存）。所以解决方法是创建一个新实例，并用这个新创建的实例设置变量team，然后将玩家添加到它并添加到DivisionOne。

Answer 3

我在尝试让它工作时遇到了无穷无尽的麻烦。一个特别的 我遇到的问题是每次创建团队对象时， 并为其添加一个玩家对象，然后创建另一个团队对象并 另一名球员，但如果我列出该新球队的球员，它会显示 前一名球员和新球员一样加入了第一支球队。

确保团队对象不共享任何字段。也许您在包含球员的列表中使用“静态”字段？如果您声明一个字段为静态，它将在所有团队实例之间共享，这可能不是您想要的。

Answer 4

查看您的代码会有所帮助，但鉴于您的描述，我想以这样的示例开始：

// Team.java
public class Team {
   private String name;
   private List<Player> players;

   public Team(String name) {
      this.name = name;
      this.players = new ArrayList<Player>();
   }

   public String getName() {
       return name;
   }

   public List<Player> getPlayers() {
       return players;
   }
}

// Player.java
public class Player {
   private String name;

   public Player(String name) {
      this.name = name;
   }

   public String getName() {
      return name;
   }
}

// Main.java
public class Main {
   public static void main(String[] args) {
      Team team1 = new Team("Team #1");
      Team team2 = new Team("Team #2");
      team1.getPlayers().add(new Player("Bob"));
      team2.getPlayers().add(new Player("Joe"));
   }
}

Answer 5

我同意@Kaleb 的回答，但我会给你一个替代方案（如果你愿意的话）......

public class Player {
    private String name;
    protected int speed;
    protected int health;

    public Player(String name, int speed, int health) {
        this.name = name;
        this.speed = speed;
        this.health = health;
    }
}

public class Main {
    public static void main(String[] args) {
        Map<Player> team1 = new HashMap<Player>();
        Map<Player> team2 = new HashMap<Player>();
        System.out.print("Enter the name of the player followed by its speed, health, and team number:");
        java.util.Scanner sc = new java.util.Scanner(System.in).useDelimiter(",");
        String name = sc.next();
        int speed = sc.nextInt();
        int health = sc.nextInt();
        if (sc.nextInt() == 1) {
            team1.put(new Player(name, speed, health));
        } else {
            team2.put(new Player(name, speed, health));
        }
    }
}