Java枚举 - 在定义之前不能引用字段

问题描述

我有一个类似下面的枚举，但eclipse说每个相对对的第一个定义有错误。

  public enum Baz {
 yin（yang），//在定义之前无法引用字段
 yang（yin），
 good（evil），//在定义之前不能引用一个字段
 evil（good）; 
 
 public final Baz对面; 
 
 Baz（Baz对面）{
 this.opposite =对面; 
} 
} 
  

我想要完成的是能够使用 Baz.something.opposite 以获得 Baz.something 的相对对象。这有可能的解决方法吗？也许在 yang 和之前的空白占位符之前 yin 和 good 在本例中定义

解决方案

：

  public enum Baz {
 yin（yang），
 yang（yin） ，
 good（evil），
 evil（good）; 
 
 private String对面; 
 
 Baz（String对面）{
 this.opposite =对面; 
} 
 
 public Baz getOpposite（）{
 return Baz.valueOf（opposite）; 
} 
} 
  

然后将其引用为

  Baz.something.getOpposite（）
  

这应该通过查找枚举值来完成你想要做的，它的字符串表示形式。我不认为你可以使用Baz的递归参考。

I have an enum like the one below, but eclipse says that there are errors in the first definition of each opposite pair.

public enum Baz{
  yin(yang),    //Cannot reference a field before it is defined
  yang(yin),
  good(evil),   //Cannot reference a field before it is defined
  evil(good);

  public final Baz opposite;

  Baz(Baz opposite){
    this.opposite = opposite;
  }
}

What I want to accomplish is being able to use Baz.something.opposite to get the opposite object of Baz.something. Is there a possible workaround for this? Maybe an empty placeholder for yang and bad before yin and good are defined in this example?

解决方案

You could try something like:

public enum Baz{
  yin("yang"),
  yang("yin"),
  good("evil"),
  evil("good");

  private String opposite;

  Baz(String opposite){
    this.opposite = opposite;
  }

  public Baz getOpposite(){
     return Baz.valueOf(opposite);
  }
}

and then reference it as

Baz.something.getOpposite()

That should accomplish what you are looking to do by looking up the enum value by it's string representation. I don't think you can get it to work with the recursive reference to Baz.

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