Java 自定义枚举值到枚举
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Java custom enum value to enum
提问by xmen
I have enum like this
我有这样的枚举
public enum Sizes {
Normal(232), Large(455);
private final int _value;
Sizes(int value) {
_value = value;
}
public int Value() {
return _value;
}
}
Now I can call Sizes.Normal.Value() to get integer value, but how do I convert integer value back to enum?
现在我可以调用 Sizes.Normal.Value() 来获取整数值，但是如何将整数值转换回枚举？
What I do now is:
我现在要做的是：
public Sizes ToSize(int value) {
for (Sizes size : Sizes.values()) {
if (size.Value() == value)
return size;
}
return null;
}
But that's only way to do that? That's how Java works?
但这只是这样做的方法吗？这就是Java的工作原理？
回答by bmargulies
Yes that's how it's done, generally by adding a static method to the enum. Think about it; you could have 10 fields on the enum. Do you expect Java to set up lookups for all of them?
是的，就是这样做的，通常是通过向枚举添加静态方法。想一想；枚举上可以有 10 个字段。您是否希望 Java 为所有这些设置查找？
The point here is that Java enums don't have a 'value'. They have identity and an ordinal, plus whatever you add for yourself. This is just different from C#, which follows C++ in having an arbitrary integer value instead.
这里的重点是 Java 枚举没有“值”。他们有身份和序数，加上你为自己添加的任何东西。这与 C# 不同，后者遵循 C++ 具有任意整数值。
回答by mgibsonbr
It's been a while since I last worked with Java, but if I recall correctly, there's no relation between your _valuefield and the enum's ordinal. AFAIK you could have two entries with the same _value, for instance. As @bmargulies pointed out, you could have many fields in the enum, and nothing constrain you to use distinct values for each (or all) of them.
我上次使用 Java 已经有一段时间了，但如果我没记错的话，你的_value字段和枚举的序数之间没有关系。AFAIK 你可以有两个相同的条目_value，例如。正如@bmargulies 所指出的，枚举中可以有许多字段，并且没有什么限制您为每个（或所有）字段使用不同的值。
See also this related question. Apparently, you can't directly set the ordinal of your entries.
另请参阅此相关问题。显然，您不能直接设置条目的序号。
