java - 一个对象拥有另一个对象

Question

目前我正在使用 Java 设计一个大富翁游戏。

游戏中的每个玩家都可以拥有不同的属性。我遇到的问题是如何为每个玩家分配不同的属性对象。我有一个 Player 类和一个 Properties 类。组合是最好的方法吗？如果是这样，我会怎么做？

Answer 1

我会添加一个新类 PropertyManager。

这使您可以轻松地在单个位置提供业务规则（良好的关注点分离），而如果您选择组合，则不必深入研究一堆玩家或属性对象。这将使 Player 和/或 Property 类在未来不会被买卖业务规则所拖累。

public final class PropertyManager {

  /**
   * The PropertyManager instance, example usage:
   *   PropertyManager.INSTANCE.buyProperty(property, buyer);
   * NB: Good candidate for dependency injection instead if you are doing this.
   */
  public static final PropertyManager INSTANCE = new PropertyManager();

  private static final Map<Property, Player> propertyListing = new HashMap<Property, Player>();

  /**
   * Buy a property from the banker, banker or property manager could maintain
   * Collection of available properties
   */
  public void buyProperty(Player buyer, Property property) {
    if (propertyListing.containsKey(property)) {
      throw new IllegalStateException("Unable to buy unless owner sells it");
    }
    propertyListing.put(property, buyer);
  }

  /**
   * Broker a transaction between two players for the sale of a property
   */
  public void sellProperty(Player seller, Player buyer, Property property) {
    if (!propertyListing.containsKey(property)) {
      throw new IllegalStateException("Unable to sell Property which is not owned");
    }
    Player owner = propertyListing.get(property);
    if (!owner.equals(seller)) {
      throw new IllegalStateException("Unable to sell property seller doesn't own");
    }
    // TODO : Deduct/transfer monies (ensure sufficient value in buyer account etc)
    propertyListing.put(property, buyer); 
  }

  /**
   * Retrieve a List of all of the Player's properties
   */
  public List<Property> getProperties(Player owner) {
    // TODO Either iterate through the propertyListing or use a second Map for player to List<Property>, NB: they should be guarded with a shared lock if you do this (threading).
  }

  /**
   * Retrieve the owner of a Property or null if it is unowned
   */
  @Nullable // javax annotation indiciates can be null
  public Player getOwner(Property property) {
    return propertyListing.get(property);
  }

  /**
   * Hide the constructor as the only property manager should be INSTANCE
   */
  private PropertyManager() {
    // Prevent further instantiation
  }
}

Answer 2

用现实世界的术语来思考它。

当您在玩大富翁游戏并购买房产时，您会拿起房产卡并将其添加到您面前的房产列表中。

因此，在这种情况下，您是一个将 Property 对象添加到您的属性列表的 Player 对象。

public class Player
{
    private List<Property> properties;
}

Answer 3

作曲作品。只要玩家有一个属性对象，并且属性对象包含所有必要的数据，你应该没问题（假设你实现了必要的 getter 和 setter 方法）。

Answer 4

该属性可以有一个 Owner 属性，即 Player。

您还可以在属性播放器上建立一个列表。

Answer 5

您将需要组合和多态性。

假设一个玩家可以拥有多个属性，您将需要一个属性列表。如果属性的属性不同，您可以应用多态和继承。您可能只会在下面看到继承，但是当您获取不同的属性并对其进行操作时，您将需要多态性。

主要：

public static void main(String args[]){
  Player player1 = new Player();

  BlackProperty blackProperty = new BlackProperty();
  BlueProperty blueProperty = new BlueProperty();

  player1.addProperty(blackProperty);
  player1.addProperty(blueProperty);
}

您所有的域类：

public class Player{
  private List<Properties> propertyList;

  // getters and setters

  public void addProperty(Properties properties){
    if(this.propertyList == null){
      this.propertyList = new ArrayList<Properties>();
    }

    this.propertyList.add(properties);
  }
}

public class Properties{
  private int noOfFloor;
  // getters and setters
}

public class BlackProperty extend Properties{
  private String noOfGate;
  // getters and setters
}

public class BlueProperty extend Properties{
  private String noOfLawn;
  // getters and setters
}