如何在Java 8中用Enums重用重复代码? [英] How to re-use duplicate code with Enums in Java 8?

问题描述

我的应用程序中有3个枚举器类.这3个类都有2个重复的方法，我们希望在实现的每个枚举中都可以使用它们.

I have 3 enumerator classes in my application. All 3 classes have 2 duplicate methods that we want available in every enum that we implement.

public static List<String> supported(){
    return Arrays.asList([[EnumClass]].values())
                 .stream().map(Enum::name).collect(Collectors.toList());
}

public static boolean contains(String value){

    boolean response = false;

    try {
        response = value != null ? [[EnumClass]].valueOf(value.trim().toUppercase()) != null : false;

    } catch (Exception e){
        LOGGER.error("ERROR: {}", e);
    }
    return response;
}

这些方法中唯一更改的部分是 EnumClass ，它是每个枚举的类.

The only part of these methods that changes is the EnumClass which is the class of each enum.

第一个方法将打印枚举类的所有可能值，第二个方法如果可以将给定的String制成枚举类，则返回true/false.

The first method will print all the possible values for the enum class and the second method will return true/false if the given String can be made into the enum class.

我试图实现实现这些方法的接口，但是我不能使用values()，因为它不是Enum API的一部分.我不能将这些方法与每个类特别相关，因为这些方法是公共静态的.由于Java不支持多重继承，因此无法创建自定义类并扩展Enum来扩展它.

I tried to implement an Interface that implemented these methods, but I can't use values() because it's not part of the Enum API. I can't relate the methods to each class specifically because the methods are public static. I can't create a custom class and extend Enum to extend that since Java doesn't support multiple inheritance.

与此同时，我的代码可以正常工作，但是重复确实困扰着我，我觉得它可以做得更好.如果我们继续添加新的枚举数，那么重复将变得更糟.

For the meanwhile I have my code working, but the duplication really bothers me and I feel like it can be way better. If we continue to add new enumerators then the duplication will just get worse.

推荐答案

您不能让Enum类实现接口，但是可以在每个枚举上保留对对象的静态引用，并且这些对象可以实现公共接口.这样可以减少重复的次数.

You cannot have the Enum class implement an interface, but you can keep a static reference to an object on each enum, and those objects can implement a common interface. This will reduce the amount of duplication.

public static class EUtils<E extends Enum<E>> {

    private final E[] values;
    private Function<String,E> valueOf;

    public EUtils(E[] values, Function<String,E> valueOf) {
        this.values = values;
        this.valueOf = valueOf;
    }

    public List<String> supported(){
        return Arrays.asList(values)
                     .stream().map(Enum::name).collect(Collectors.toList());
    }

    public boolean contains(String value){

        boolean response = false;

        try {
            response = value != null ? valueOf.apply(value.trim().toUpperCase()) != null : false;

        } catch (Exception e){
            e.printStackTrace();
        }
        return response;
    }
}



private enum Directions {
    LEFT,
    RIGHT;

    public static EUtils<Directions> enumUtils = new EUtils<>(Directions.values(),Directions::valueOf);

}


public static void main(String[] args) {
    System.out.println(Directions.enumUtils.contains("LEFT"));
    System.out.println(Directions.enumUtils.contains("X"));
}

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