Java：在子类下使用带有枚举的switch语句 [英] Java: using switch statement with enum under subclass

问题描述

首先我会说明我对C＃中的枚举非常熟悉，而且java中的枚举似乎很麻烦。

正如你所见，我试图在下一个例子中使用一个switch语句@枚举，但总是会收到一个错误，无论我在做什么。

错误我收到的是：

合格案例标签 SomeClass.AnotherClass.MyEnum.VALUE_A 必须被替换为不合格的枚举常量 VALUE_A

事情是我相当了解错误，但是我不能仅仅写入一个VALUE_A，因为枚举位于另一个子类中。有没有办法解决这个问题？为什么会发生在Java中？

  //主类
 public class SomeClass {
 
 //子类
 public static class AnotherClass {
 public enum MyEnum {
 VALUE_A，VALUE_B 
} 
 public MyEnum myEnum; 
} 
 
 public void someMethod（）{
 MyEnum enumExample // ... 
 
 switch（enumExample）{
 case AnotherClass。 MyEnum.VALUE_A：{<  - 此行上的错误
 // .. 
 break; 
} 
} 
} 
} 
  

解决方案

将其更改为：

  switch（enumExample）{
 case VALUE_A： {
 // .. 
 break; 
} 
} 
  

线索在错误中。您不需要符合案例标签与枚举类型，只是其值。

First I'll state that I'm much more familiar with enums in C# and it seems like enums in java is a quite mess.

As you can see, I'm trying to use a switch statement @ enums in my next example but I always get an error no matter what I'm doing.

The error I receive is:

The qualified case label SomeClass.AnotherClass.MyEnum.VALUE_A must be replaced with the unqualified enum constant VALUE_A

The thing is I quite understand the error but I can't just write the VALUE_A since the enum is located in another sub-class. Is there a way to solve this problem? And why is it happening in Java?

//Main Class
public class SomeClass {

    //Sub-Class
    public static class AnotherClass {
        public enum MyEnum {
            VALUE_A, VALUE_B
        }    
        public MyEnum myEnum;
    }

    public void someMethod() { 
        MyEnum enumExample //...

        switch (enumExample) {
            case AnotherClass.MyEnum.VALUE_A: { <-- error on this line
                //..
                break;
            }
        }
    }
}

解决方案

Change it to this:

switch (enumExample) {
    case VALUE_A: {
        //..
        break;
    }
}

The clue is in the error. You don't need to qualify case labels with the enum type, just its value.

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