在枚举类的方法中使用类中的哈希集

Question

我有以下枚举类字符和枚举类项：

public enum Item
{
COOKIE("cookie"), CRISPS("crisps"), DRINK("drink");    
private String description;    
/**
 * Constructor with description and weight.
 * Pre-condition: description not null.
 */
private Item(String description)
{
    assert description != null : "Item.Item with null description";
    this.description = description;
    sane();
}

字符：

public enum Character
{
JESS("Jess", 0.5f,Item.SANDWICH), SALLY("Sally",0.5f, Item.CRISPS), 
ANDREW("Andrew" ,0.5f,Item.DRINK), 
ALEX("Alex",0.5f,null),CookieMonster("CookieMonster",1.0f,null),
CookieGiver("CookieGiver",1.0f,null),Player("Player",0.0f,null);
private String description;
private ArrayList<Item> charItems = new ArrayList<Item>();
private float probability;
/**
 * Constructor initialising description,item and probability.
 */
private Character(String desc,float moveProbability,Item items)
{
    description= desc;
    charItems.add(items);
    probability =moveProbability;
}
public void enterRoom(Room r)
{
}

以下是用于创建 Room 对象的类

  public class Room 
  {
private String description;
private HashMap<Direction, Room> exits;        // stores exits of this room.
private Set<Character> chars;  // stores the characters that are in this 
room.
/**
 * Create a room described "description". Initially, it has
 * no exits. "description" is something like "a kitchen" or
 * "an open court yard".
 * @param description The room's description.
 * Pre-condition: description is not null.
 */
public Room(String description) 
{
    assert description != null : "Room.Room has null description";
    this.description = description;
    exits = new HashMap<Direction, Room>();
    chars = new HashSet<Character>();
    sane();
}

我将如何在枚举类中编写一个方法，例如当调用时，CookieGiver 将物品 COOKIE 提供给房间中的每个角色？

我知道不知何故我需要使用 HashSet 字符，但我想不出一种方法来做到这一点。

Answer 1

向Room添加一个 getter 以获取房间中的角色列表

public Set<Character> getChars() {           
     return chars;                            
}                                            

将方法添加到字符枚举以将项目添加到已持有的项目列表中。

private void addItem(Item item) {            
    charItems.add(item);                    
}                                           

在enterRoom方法中，对于房间中的每个字符，调用addItem，向其添加 COOKIE。

注意：如果多次调用，它将添加多个 COOKIE。如果您不希望这样做，则必须检查 COOKIE 是否已经存在或使用 Set。

public void enterRoom(Room r) {              
    for(Character character : r.getChars()) {
        character.addItem(Item.COOKIE);      
}                                        

编辑：

由于您希望上述策略仅适用于CookieGiver，一种方法是将enterRoom的默认逻辑设为空，并将其覆盖为 CookieGiver 。

public void enterRoom(Room r) { } //empty / no-op in enum
CookieGiver("CookieGiver", 1.0f, null) {           
@Override                                      
public void enterRoom(Room r) {                
    for (Character character : r.getChars()) { 
        character.addItem(Item.COOKIE);        
    }                                          
}                                              

选项 2：
您可以创建一个私有嵌套枚举，其中包含调用enterRoom时要执行的操作的策略。然后每个角色都会有一个针对它的策略。

public enum Character {
    JESS("Jess", 0.5f, Item.CRISPS, RoomStrategy.NONE),  //when enterRoom is called on this Character, then there is nothing to do
    CookieMonster("CookieMonster", 1.0f, null, RoomStrategy.NONE),
    CookieGiver("CookieGiver", 1.0f, null, RoomStrategy.PROVIDE_COOKIE), //when enterRoom is called on this Character, then invoke the logic corresponding to PROVIDE_COOKIE
    private String description;
    private ArrayList<Item> charItems = new ArrayList<Item>();
    private float probability;
    private RoomStrategy roomStrategy; //Field to hold the strategy
    /**
     * Constructor initialising description,item and probability.
     */
    private Character(String desc, float moveProbability, Item items, RoomStrategy roomStrategy) {
        description = desc;
        charItems.add(items);
        probability = moveProbability;
        this.roomStrategy = roomStrategy;
    }
    private void addItem(Item item) {
        charItems.add(item);
    }
    public void enterRoom(Room r) {
        roomStrategy.enterRoom(r); //Just delegate to the strategy
    }

    private enum RoomStrategy { //better name needed?
        NONE {
            @Override
            void enterRoom(Room r) {
               //No op
            }
        },
        PROVIDE_COOKIE {
            @Override
            void enterRoom(Room r) {
                for (Character character : r.getChars()) {
                    character.addItem(Item.COOKIE);
                }
            }
        };
        abstract void enterRoom(Room r);
    }
}

注意：按照评论中的建议，有更好的方法可以做到这一点。