如何在Java中按字母顺序排列枚举成员？ [英] How do I sort enum members alphabetically in Java?

问题描述

  public enum Letter {
 OMEGA_LETTER（Omega） ，
 GAMMA_LETTER（Gamma），
 BETA_LETTER（Beta），
 ALPHA_LETTER（Alpha），
 
 private final String description; 
 
 Letter（）{
 description = toString（）; 
} 
 
 Letter（String description）{
 this.description = description; 
} 
 
 public String getDescription（）{
 return description; 
} 
} 
  

稍后我的代码我基本上迭代了字母枚举并将其成员打印到控制台：

  for（Letter letter：Letter.values（））{
系统.out.println（letter.getDescription（））; 
} 
  

我以为values（）方法会给我一个有序的视图枚举（如 here 所述），但这不是这里的情况。我只是按照我在Letter枚举类中创建的顺序获取枚举成员。有没有办法按字母顺序输出枚举值？我需要一个单独的比较对象，还是有内置的方式来做到这一点？基本上我希望按照getDescription（）文本按字母顺序排序值：

  Alpha 
 Beta 
 Gamma 
欧米茄
  

解决方案

  SortedMap< String，Letter> map = new TreeMap< String，Letter>（）; 
（Letter l：Letter.values（））{
 map.put（l.getDescription，l）; 
} 
 return map.values（）; 
  

或者只是重新排序声明： - ）

编辑：正如KLE指出的那样，这假设说明在枚举中是唯一的。

I have an enum class like the following:

public enum Letter {
    OMEGA_LETTER("Omega"), 
    GAMMA_LETTER("Gamma"), 
    BETA_LETTER("Beta"), 
    ALPHA_LETTER("Alpha"), 

    private final String description;

    Letter() {
      description = toString();
    }

    Letter(String description) {
      this.description = description;
    }

    public String getDescription() {
      return description;
    }
}

Later down my code I basically iterate over the Letter enum and print its members out to the console:

for (Letter letter : Letter.values()) {
System.out.println(letter.getDescription());
}

I thought that the values() method would give me an ordered view of the enum (as mentioned here), but this is not the case here. I simply get the enum members in the order I created them within the Letter enum class. Is there a way to output the values of an enum in alphabetical order? Would I need a separate comparator object, or is there a built-in way to do this? Basically I would like the values to be alphabetically sorted based on the getDescription() text:

Alpha
Beta
Gamma
Omega

解决方案

SortedMap<String, Letter> map = new TreeMap<String, Letter>();
for (Letter l : Letter.values()) {
    map.put(l.getDescription, l);
}
return map.values();

Or just reorder the declarations :-)

Edit: As KLE pointed out, this assumes that the Descriptions are unique within the enum.

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