Java 中 Enum 枚举类的使用技巧

 

使用Enum类做配置类

原理：

位运算符

参考：C/Cpp中的位运算符 - htj10 - 博客园 (cnblogs.com)

 

GoodFeature 类

（从 fastjson-1.2.47.jar 里的 SerializerFeature 学习到的）

package test;

/**
 * 配置类、开关类
 * @author John
 *
 */
public enum GoodFeature {
    AFeature,//A
    BFeature,
    CFeature;
    
    private final int mask;

    private GoodFeature() {
        this.mask = (1 << ordinal());
    }

    public final int getMask() {
        return this.mask;
    }
    

    public static boolean isEnabled(int features, GoodFeature feature) {
        return (features & feature.getMask()) != 0;
    }

    public static boolean isEnabled(int features, int fieaturesB, GoodFeature feature) {
        int mask = feature.getMask();

        return ((features & mask) != 0) || ((fieaturesB & mask) != 0);
    }

    /**
     * 打开或关闭对应的开关（特征）
     * @param features 原来的开关（特征）（可以从 of() 获得）
     * @param feature  需要打开或关闭的开关（特征）
     * @param state true:打开 false:关闭
     * @return
     */
    public static int config(int features, GoodFeature feature, boolean state) {
        if (state)
            features |= feature.getMask();
        else {
            features &= (feature.getMask() ^ 0xFFFFFFFF);
        }

        return features;
    }

    public static int of(GoodFeature[] features) {
        if (features == null) {
            return 0;
        }

        int value = 0;

        for (GoodFeature feature : features) {
            value |= feature.getMask();
        }

        return value;
    }

}

测试Demo

    private static void test2() {
        GoodFeature a = GoodFeature.AFeature;
        GoodFeature b = GoodFeature.BFeature;
        GoodFeature c = GoodFeature.CFeature;
        
        System.out.println(a.ordinal());//0
        System.out.println(b.ordinal());//1
        System.out.println(c.ordinal());//2

        System.out.println(a.getMask());//1
        System.out.println(b.getMask());//2
        System.out.println(c.getMask());//4
        System.out.println("-----------------");
        //打开 
        int c1 = GoodFeature.config(0, a, true);
        int c2 = GoodFeature.config(c1, b, true);
        int c3 = GoodFeature.config(c2, c, true);
        //
        System.out.println(c3);//7
        int abc = GoodFeature.of(new GoodFeature[] { GoodFeature.AFeature,GoodFeature.BFeature,GoodFeature.CFeature });
        System.out.println(abc);//7
        System.out.println("-----------------");
        System.out.println(GoodFeature.isEnabled(c3, GoodFeature.AFeature));//true
        System.out.println(GoodFeature.isEnabled(c3, GoodFeature.BFeature));//true
        System.out.println(GoodFeature.isEnabled(c3, GoodFeature.CFeature));//true
        c3 = GoodFeature.config(c3, GoodFeature.AFeature, false);//关闭A特性
        c3 = GoodFeature.config(c3, GoodFeature.BFeature, false);//关闭B特性
        System.out.println(GoodFeature.isEnabled(c3, GoodFeature.AFeature));//false
        System.out.println(GoodFeature.isEnabled(c3, GoodFeature.BFeature));//false
        System.out.println(GoodFeature.isEnabled(c3, GoodFeature.CFeature));//true
    }