java 如何将方法参数声明为任何枚举
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How to declare a method parameter as any enum
提问by popcoder
I have a method on which I need to pass an enum as a parameter.
我有一个方法，我需要将枚举作为参数传递给它。
public <T> T doSomething(SomeEnum operation, Class<T> something);
I have several enums and the method is a common one which should work with any enums. What is the correct way to write this method signature to accept any generic enum types? I know that I can use a marker interface to this purpose, but I would like to write it with generic enum signatures. Please advise me on this.
我有几个枚举，该方法是一个通用的，应该适用于任何枚举。编写此方法签名以接受任何通用枚举类型的正确方法是什么？我知道我可以为此目的使用标记接口，但我想用通用枚举签名来编写它。请就此给我建议。
Whats the bad idea with the below one: (It works but I get warnings from IDE saying it is a raw type. I'm not clear about the reason).
下面的一个坏主意是什么：（它有效，但我收到来自 IDE 的警告，说它是原始类型。我不清楚原因）。
public void doSomething(Enum operation);
回答by Istvan Devai
public <E extends Enum<E>> void doSomething(E operation);
EDIT: An example according to your modifications:
编辑：根据您的修改示例：
public class Main {
public enum Day {
SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
THURSDAY, FRIDAY, SATURDAY
}
public <E extends Enum<E>> E doSomething(E operation, Class<E> klazz) {
return operation;
}
public static void main(String[] args) {
new Main().doSomething(Day.FRIDAY, Day.class);
}
}
EDIT2:
编辑2：
if you need T and the Enum as separate types, then you'll need:
如果您需要 T 和 Enum 作为单独的类型，那么您将需要：
public <T, E extends Enum<E>> T doSomething(E operation, Class<T> klazz) {
回答by Reverend Gonzo
You could do:
你可以这样做：
public void doSomething(final Enum<?> operation);
which says it needs to be an enum, but not any specific one.
它说它需要是一个枚举，但不是任何特定的枚举。
回答by Ahmed Gamal
This one is more cleared :
这个更清楚：
public class EnumTest {
protected static <E extends Enum<E>> void enumValues(Class<E> enumData) {
for (Enum<E> enumVal: enumData.getEnumConstants()) {
System.out.println(enumVal.toString());
}
}
public static enum TestEnum {
ONE, TWO, THREE;
}
public static void main(String param [] ) {
EnumTest.enumValues(EnumTest.TestEnum.class);
}
}
