获取与int值相关联的枚举 [英] Getting enum associated with int value

问题描述

以前，我的LegNo枚举简单地定义为：

Previously, I had my LegNo enums defined simply as:

NO_LEG, LEG_ONE, LEG_TWO

并通过调用返回LegNo.values（）[i]; ，I能够获得与每个枚举相关联的值。

and by calling return LegNo.values()[i];, I was able to get the value associated with each enum.

但现在我决定要$ LegNo 枚举 NO_LEG 成为int -1而不是0
所以我决定使用一个私有构造函数来初始化并设置其int值

But now I've decided I want the LegNo enum NO_LEG to be the int -1 instead of 0 so I decided to use a private constructor to initialise and set its int value

NO_LEG(-1), LEG_ONE(1), LEG_TWO(2);

private LegNo(final int leg) { legNo = leg; }

现在唯一的一件事是因为我这样做， > values（）方法将不适用于 NO_LEG 枚举。如何获取与int关联的枚举？有没有任何有效的方式来做这个，而不是使用案例切换语句或if-elseif-elseif

the only thing now is that because I'm doing it this way the values() method will not work for the NO_LEG enum. How do I get the enum associated with the int? Is there any efficient way of doing this other than using a case switch statement or an if-elseif-elseif

我可以看到很多SO问题， int值从枚举，但是我反过来。

I can see a lot of SO questions to do with getting the int value from the enum, but that I'm after the reverse.

推荐答案

您必须在枚举中保留一个映射。

You'll have to maintain a mapping inside the enum.

public enum LegNo {
    NO_LEG(-1), LEG_ONE(1), LEG_TWO(2);

    private int legNo;

    private static Map<Integer, LegNo> map = new HashMap<Integer, LegNo>();

    static {
        for (LegNo legEnum : LegNo.values()) {
            map.put(legEnum.legNo, legEnum);
        }
    }

    private LegNo(final int leg) { legNo = leg; }

    public static LegNo valueOf(int legNo) {
        return map.get(legNo);
    }
}

静态块只会调用一次，所以在这里几乎没有性能问题。

The static block will be invoked only once, so there is practically no performance issue here.

编辑：将方法重命名为 valueOf ，因为它与其他Java课程。

Renamed the method to valueOf as it is more inline with other Java classes.

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