枚举共享静态查找方法 [英] Enums shared static look-up method

问题描述

我有以下枚举：

public enum MyEnum{
    A(10, "First"), //
    B(20, "Second"), //
    C(35, "Other options");

    private Integer code;
    private String description;

    private MyEnum(Integer code, String description) {
        this.code = code;
        this.description = description;
    }

    public Integer getCode() {
        return code;
    }

    public String getDescription() {
        return description;
    }

    public static MyEnum getValueOf(Integer code) {
        for (MyEnum e : MyEnum.values()) {
            if (e.getCode().equals(code)) {
                return e;
            }
        }
        throw new IllegalArgumentException("No enum const " + MyEnum.class.getName() + " for code \'" + code
                + "\'");
    }
}

哪个工作正常。 getValueOf -method存在是因为当与外部合作伙伴进行通信时，我们只获取代码（他们选择）映射到。我需要描述，因为我需要在GUI中显示一个有意义的短语。

Which works fine. The getValueOf-method exists because when communicating with an external partner, we only get the code (they chose) to map to. I need the description because I need to show a meaningfull phrase in the GUI.

但是我现在有一些类似的枚举类。所有人都有自己的代码描述，并且它们需要相同的查找功能。
我希望 getValueOf -method是通用的，所以我不需要支持基于相同方法的30多个不同的枚举。

But I now have a number of similar enum classes. All having their own code & description, and they need the same lookup functionality. I wanted the getValueOf-method to be generic so I don't need to support 30+ different enums for basically the same method.

为了解决这个问题，我想使一个抽象类定义这个方法并实现一些常见的逻辑，但这是不可能的，因为我不能扩展枚举。

To solve this I wanted to make an abstract class to define this method and implement some of the common logic but this is impossible because I can't extend Enum.

然后，我尝试使用以下方法创建一个Utility类：

Then I tried to make a Utility class with the following method:

public static <T extends Enum<T>> T getValueOf(Enum<T> type, Integer code) {...}

但是枚举与枚举令人困惑，我不明白如何使这个工作。

But generics with Enums are confusing and I don't understand how to get this working.

基本上我想知道的是：什么是一个很好的方法来定义一个常见的实用程序到枚举？

Basically what I want to know is: What is a good approach to define a common utility to an enum?

推荐答案

您需要将实际的枚举类对象作为参数传递给您的方法。然后，您可以使用 Class.getEnumConstants（）获取枚举值。

You need to pass the actual enum class object as a parameter to your method. Then you can get the enum values using Class.getEnumConstants().

为了能够访问 getCode（）在实例上，您应该在界面中定义它，并使所有的枚举类型实现该接口：

In order to be able to access getCode() on the instances, you should define it in an interface and make all your enum types implement that interface:

interface Encodable {
    Integer getCode();
}

public static <T extends Enum<T> & Encodable> T getValueOf(Class<T> enumClass, Integer code) {
    for (T e : enumClass.getEnumConstants()) {
        if (e.getCode().equals(code)) {
            return e;
        }
    }
    throw new IllegalArgumentException("No enum const " + enumClass.getName() + " for code \'" + code
            + "\'");
}

...

public enum MyEnum implements Encodable {
    ...
}

MyEnum e = getValueOf(MyEnum.class, 10);

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