Java：枚举的通用方法
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原文地址: http://stackoverflow.com/questions/16406298/
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Java: Generic method for Enums
提问by Alexander Mills
Help me understand generics. Say I have two enums as inner classes like so:
帮助我理解泛型。假设我有两个枚举作为内部类，如下所示：
public class FoodConstants {
public static enum Vegetable {
POTATO,BROCCOLI,SQUASH,CARROT;
}
public static enum Fruit {
APPLE,MANGO,BANANA,GUAVA;
}
}
Instead of having both enums implement an interface, and have to implement the same method twice, I would like to have a method in the outer class that does something like:
与其让两个枚举都实现一个接口，并且必须两次实现相同的方法，我希望在外部类中有一个方法，它可以执行以下操作：
public <e> String getEnumString<Enum<?> e, String s) {
for(Enum en: e.values()) {
if(en.name().equalsIgnoreCase(s)) {
return s;
}
}
return null;
}
However this method does not compile. What I am trying to do is find out if a string value is the name of an enumerated value, in ANY enum, whether it's Vegetable, Fruit, what not. Regardless of whether this is in fact a redundant method, what is wrong with the one I am trying to (re)write?
但是，此方法无法编译。我想要做的是找出字符串值是否是枚举值的名称，在任何枚举中，无论是蔬菜、水果，还是什么。不管这实际上是否是一种多余的方法，我试图（重新）编写的方法有什么问题？
Basically I would like to do this:
基本上我想这样做：
public class FoodConstants {
public static enum Vegetable {
POTATO,BROCCOLI,SQUASH,CARROT;
}
public static enum Fruit {
APPLE,MANGO,BANANA,GUAVA;
}
public <e> String getEnumString<Enum<?> e, String s) {
for(Enum en: e.values()) {
if(en.name().equalsIgnoreCase(s)) {
return s;
}
}
return null;
}
} //end of code
采纳答案by Mike Samuel
public static <E extends Enum<E>>
String getEnumString(Class<E> clazz, String s){
for(E en : EnumSet.allOf(clazz)){
if(en.name().equalsIgnoreCase(s)){
return en.name();
}
}
return null;
}
The original has a few problems:
原文有几个问题：
- It accepts an instance of the enum instead of the class representing the enum which your question suggests you want to use.
- The type parameter isn't used.
- It returns the input instead of the instance name. Maybe returning the instance would be more useful -- a case-insensitive version of
Enum.valueOf(String). - It calls a static method on an instance so you can iterate.
EnumSetdoes all the reflective stuff for you.
- 它接受枚举的实例，而不是代表您的问题建议您要使用的枚举的类。
- 未使用类型参数。
- 它返回输入而不是实例名称。也许返回实例会更有用——不区分大小写的
Enum.valueOf(String). - 它在实例上调用静态方法，以便您可以进行迭代。
EnumSet为你做所有反射性的东西。
