写入方法，可获取/返回任何枚举的枚举常量 [英] Write method that takes/returns enum constants of any enum

问题描述

当我存储配置枚举时，只要将它绑定到特定的枚举类型 MyEnum ：

When I store a configuration enum, this is easy as long as it is type-bound to, say, a special enum type MyEnum:

void storeMyEnumValue(MyEnum value) {
    String valueString = value.name();
    // Store valueString somewhere
}

MyEnum loadMyEnumValue(MyEnum fallbackValue) {
    // Load valueString from somewhere
    try {
        return MyEnum.valueOf(valueString);
    } catch (Exception e) {
        return fallbackValue;
    }
}

但是如果我想将其归纳并得到一个

的 store / load 方法的集合？

But what if I want to generalize that and have a set of store/load methods for any type of enum?

void storeAnyEnumValue(??? value) {
    // The same as before
}

??? loadAnyEnumValue(??? defaultValue) {
    // The same as before
}

因此，您可以看到，问题主要是通常如何处理枚举常量类型的对象。

So as you can see, the question is mainly how to handle "objects of the type enum constant" in general.

推荐答案

对于store方法，您可以仅使用 Enum<？> 的实例。

For the store method, you can just use an instance of Enum<?>. There is no advantage to a type variable here.

void storeAnyEnumValue(Enum<?> value) {
    // The same as before
}

对于load方法，您希望返回类型为与 defaultValue 具有相同的类型，因此这里确实需要类型变量：

For the load method, you want the return type to be of the same type as the defaultValue, so you do need a type variable here:

<E extends Enum<E>> E loadAnyEnumValue(E defaultValue) {
    // The same as before
}

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