如何有效地使用Enum对象作为Map数据结构中的键？ [英] How to efficiently use Enum objects as keys in the Map data structure?

问题描述

解决方案

我学到了一个更有效和专门的Map集合的实现方法这最近在我不小心绊倒了Java API中的答案。如果您有一个使用枚举作为键的地图，请确保使用 EnumMap的。这很简单，而且更有效率：

  public interface LibraryItem {...} 
 
 public enum LibraryItemType {BOOK，CD，VHS，AUDIO; ...} 
 
 Map< LibraryItemType，NavigableSet< LibraryItem>> itemsByType = 
 new EnumMap<>（LibraryItemType.class）; 
  

Is there a more efficient and specialized implementation of a Map collection where Enum objects can serve as keys?

解决方案

I learned this recently after I accidentally stumbled upon the answer in the Java API. If you ever have a map that uses enums as keys make sure you use EnumMap. It's very simple and much more efficient:

public interface LibraryItem{ ... }

public enum LibraryItemType{ BOOK, CD, VHS, AUDIO; ... }

Map<LibraryItemType, NavigableSet<LibraryItem>> itemsByType =
    new EnumMap<>(LibraryItemType.class);

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