Java中枚举的实现与应用详解

public enum EnumTest {
    SUCCESS,
    FAILURE,
    EXCEPTION
}

public final class EnumTest extends Enum
{
    public static EnumTest[] values()
    {
        return (EnumTest[])$VALUES.clone();
    }
    public static EnumTest valueOf(String s)
    {
        return (EnumTest)Enum.valueOf(com/brain/demo/enumtest/EnumTest, s);
    }
    private EnumTest(String s, int i)
    {
        super(s, i);
    }
    public static final EnumTest SUCCESS;
    public static final EnumTest FAILURE;
    public static final EnumTest EXCEPTION;
    private static final EnumTest $VALUES[];
    static 
    {
        SUCCESS = new EnumTest("SUCCESS", 0);
        FAILURE = new EnumTest("FAILURE", 1);
        EXCEPTION = new EnumTest("EXCEPTION", 2);
        $VALUES = (new EnumTest[] {
            SUCCESS, FAILURE, EXCEPTION
        });
    }
}

public abstract class Enum<E extends Enum<E>>
        implements Comparable<E>, Serializable {
    private final String name;//枚举名称
    private final int ordinal;//序数，从0开始算
    protected Enum(String name, int ordinal) {
        this.name = name;
        this.ordinal = ordinal;
    }
    public String toString() {
        return name;
    }
    public final boolean equals(Object other) {
        return this==other;
    }
    protected final Object clone() throws CloneNotSupportedException {
        throw new CloneNotSupportedException();
    }
}

public static <T extends Enum<T>> T valueOf(Class<T> enumType,
                                                String name) {
        T result = enumType.enumConstantDirectory().get(name);
        if (result != null)
            return result;
        if (name == null)
            throw new NullPointerException("Name is null");
        throw new IllegalArgumentException(
            "No enum constant " + enumType.getCanonicalName() + "." + name);
    }
//Class.java
Map<String, T> enumConstantDirectory() {
        if (enumConstantDirectory == null) {
            T[] universe = getEnumConstantsShared();
            if (universe == null)
                throw new IllegalArgumentException(
                    getName() + " is not an enum type");
            Map<String, T> m = new HashMap<>(2 * universe.length);
            for (T constant : universe)
                m.put(((Enum<?>)constant).name(), constant);
            enumConstantDirectory = m;
        }
        return enumConstantDirectory;
    }
T[] getEnumConstantsShared() {
        if (enumConstants == null) {
            if (!isEnum()) return null;
            try {
                final Method values = getMethod("values");
                java.security.AccessController.doPrivileged(
                    new java.security.PrivilegedAction<Void>() {
                        public Void run() {
                                values.setAccessible(true);
                                return null;
                            }
                        });
                @SuppressWarnings("unchecked")
                T[] temporaryConstants = (T[])values.invoke(null);
                enumConstants = temporaryConstants;
            }
            // These can happen when users concoct enum-like classes
            // that don't comply with the enum spec.
            catch (InvocationTargetException | NoSuchMethodException |
                   IllegalAccessException ex) { return null; }
        }
        return enumConstants;
    }

public enum EnumTest {
    SUCCESS(0, "调用成功"),
    FAILURE(1, "调用失败"),
    EXCEPTION(-1, "调用出错");
    private int status;
    private String msg;
    EnumTest(int status, String msg) {
        this.status = status;
        this.msg = msg;
    }
    public int getStatus() {
        return status;
    }
    public void setStatus(int status) {
        this.status = status;
    }
    public String getMsg() {
        return msg;
    }
    public void setMsg(String msg) {
        this.msg = msg;
    }
    public String getDesc() {
        return status + ":" + msg;
    }
    public static void main(String[] args) {
        System.out.println(EnumTest.FAILURE.getDesc());//1:调用失败
    }
}

public enum EnumTest {
    SUCCESS(0, "调用成功") {
        @Override
        String getDesc() {
            return "恭喜调用成功";
        }
    },
    FAILURE(1, "调用失败") {
        @Override
        String getDesc() {
            return "调用失败，请重试";
        }
    },
    EXCEPTION(-1, "调用出错") {
        @Override
        String getDesc() {
            return "调用出错";
        }
    };
    private int status;
    private String msg;
    EnumTest(int status, String msg) {
        this.status = status;
        this.msg = msg;
    }
    abstract String getDesc();
    public int getStatus() {
        return status;
    }
    public void setStatus(int status) {
        this.status = status;
    }
    public String getMsg() {
        return msg;
    }
    public void setMsg(String msg) {
        this.msg = msg;
    }
}