Question

在我的聊天应用程序中，我有一个枚举：

enum ContactRelationType {
  Friend,
  Familiar,
  Ignored,
  Unknown,  
  Guild,
  Officers,
  Academy,
  Community,
  System
}

ContactRelationType值的一半是房间（公会，军官，学院，社区，系统）。我需要知道价值空间与否。

我知道有三种方法可以做到：

第一个：

enum ContactRelationType {
  Friend,
  Familiar,
  Ignored,
  Unknown,  
  Guild,
  Officers,
  Academy,
  Community,
  System;

    public boolean isRoom() {
    return this == Guild ||
        this == Officers ||
        this == Academy ||
        this == Community ||
        this == System;
  }
}

它看起来很难看，IDEA告诉我“过于复杂的布尔表达式”而且它是。

第二个：

    enum ContactRelationType {
      Friend,
      Familiar,
      Ignored,
      Unknown,  
      Guild,
      Officers,
      Academy,
      Community,
      System;

    public boolean isRoom() {
      switch (this) {
        case Guild:
        case Officers:
        case Academy:
        case Community:
        case System:
          return true;
        default:
          return false;
    }
}

它看起来也很难看。

第三个：

    public enum ContactRelationType {
      Friend(false),
      Familiar(false),
      Ignored(false),
      Unknown(false),
      Guild(true),
      Officers(true),
      Academy(true),
      Community(true),
      System(true);

      private boolean room;

      ContactRelationType(boolean room) {
        this.room = room;
      }

      public boolean isRoom() {
        return room;
      }
}

但在这种情况下，我在所有枚举实例中都有boolean room。

那么，什么解决方案更好，为什么？

Answer 1

你使用布尔标志的解决方案是好的。只需添加一个默认构造函数：

 ContactRelationType() {
    this(false);
  }

现在您不必为每个枚举成员写true或false;仅适用于那些不是“默认”的人：

public enum ContactRelationType {
  Friend,
  Familiar,
  Ignored,
  Unknown,
  Guild(true),
  Officers(true),
  Academy(true),
  Community(true),
  System(true);

Answer 2

你可能会使用EnumSet。它们使用BitSet等效项非常有效地实现。

enum ContactRelationType {

    Friend,
    Familiar,
    Ignored,
    Unknown,
    Guild,
    Officers,
    Academy,
    Community,
    System;

    public boolean isRoomRelation() {
        return RoomContacts.contains(this);
    }
}

static final Set<ContactRelationType> RoomContacts = EnumSet.of(
        ContactRelationType.Guild,
        ContactRelationType.Officers,
        ContactRelationType.Academy,
        ContactRelationType.Community,
        ContactRelationType.System);

如何获取枚举值的附加属性？

2 个答案: