Java Enum如何与C ++和传统Enum不同？ [英] How Java Enum is different then C++ and othere conventional Enum?

问题描述

解决方案

在java枚举中，我们从java 1.5获取的枚举与C ++和其他常规枚举类型不同。是复杂对象，而在C ++中，每个枚举对象都与单个整数值相关联。在java中，您可以使用与单个枚举值相关联的几个属性：

 枚举MyCategory {
 SPORT类别，sport.png），
新闻（新闻类别，news.jpg）; 
 
 private String description; 
 private String iconPath; 
 
 private MyCategory（String description，String iconPath）{
 this.description = description; 
 this.iconPath = iconPath; 
} 
 
 public String getDescription（）{
 return description; 
} 
 
 public String getIconPath（）{
 return iconPath; 
} 
} 
  

此外，在java中，您可以开关仅数字类型，字符串和枚举。然而，我无法将传统的枚举整体概括为...

编辑 java枚举可以做的另外一件事是声明每值操作（取自 java教程）：

  public enum Operation {
 PLUS {double eval（double x，double y）{return x + y; }}，
 MINUS {double eval（double x，double y）{return x  -  y; }}，
 TIMES {double eval（double x，double y）{return x * y; }}，
 DIVIDE {double eval（double x，double y）{return x / y; }}; 
 
 //做这个常数代表的算术运算
 abstract double eval（double x，double y）; 
} 
  

How the enum that we get from java 1.5 is different from C++ and other conventional Enum Type.

解决方案

In java enums are complex objects, whilst in C++ every enum object is associated with a single integer value. In java you can have several attributes associated with a single enum value:

enum MyCategory {
   SPORT("The sport category", "sport.png"),
   NEWS("the news category", "news.jpg");

   private String description;
   private String iconPath;

   private MyCategory(String description, String iconPath) {
       this.description = description;
       this.iconPath = iconPath;
   }

   public String getDescription() {
       return description;
   }

   public String getIconPath() {
       return iconPath;
   }
}

Furthermore in java you can switch only Number types, Strings and enums. However I can not generalize the conventional enums as a whole...

EDIT One more thing the java enums can do is declare per-value operation (taken from the java tutorial):

public enum Operation {
  PLUS   { double eval(double x, double y) { return x + y; } },
  MINUS  { double eval(double x, double y) { return x - y; } },
  TIMES  { double eval(double x, double y) { return x * y; } },
  DIVIDE { double eval(double x, double y) { return x / y; } };

  // Do arithmetic op represented by this constant
  abstract double eval(double x, double y);
}

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