packagejava.lang;importjava.io.Serializable;importjava.io.IOException;importjava.io.InvalidObjectException;importjava.io.ObjectInputStream;importjava.io.ObjectStreamException;/**
* 这是所有Java语言枚举类型的公共基类。
*
* 有关枚举的更多信息，包括对枚举的描述、隐式声明由编译器合成的方法，
* 可以见于<cite> Java＆trade;Language</ cite>的第8、9节。
* 另外，使用枚举类型作为set的类型或作为Map中keys的类型时，java.util.EnumSet
* 和java.util.EnumMap更加高效
*
* @param <E> The enum type subclass
* @author Josh Bloch
* @author Neal Gafter
* @see Class#getEnumConstants()
* @see java.util.EnumSet
* @see java.util.EnumMap
* @since 1.5
*/publicabstractclassEnum<EextendsEnum<E>>implementsComparable<E>,Serializable{/**
* 枚举常量的名称，和枚举声明中声明的一致。
* 大多数程序员应该使用{@link #toString}方法而不是直接访问此字段。
*/privatefinalStringname;/**
* Returns the name of this enum constant, exactly as declared in its
* enum declaration.
*
* <b>Most programmers should use the {@link #toString} method in
* preference to this one, as the toString method may return
* a more user-friendly name.</b> This method is designed primarily for
* use in specialized situations where correctness depends on getting the
* exact name, which will not vary from release to release.
*
* @return the name of this enum constant
*/publicfinalStringname(){returnname;}/**
* 这个枚举常量的序数（它在枚举声明中的位置，分配给初始常量的序数为零）。
* 大多数程序员对此字段没有使用。它是专门设计的供复杂的基于枚举的数据结构使用 * 的，例如{@link java.util.EnumSet}和{@link java.util.EnumMap}.
*/privatefinalintordinal;/**
* Returns the ordinal of this enumeration constant (its position
* in its enum declaration, where the initial constant is assigned
* an ordinal of zero).
*
* Most programmers will have no use for this method. It is
* designed for use by sophisticated enum-based data structures, such
* as {@link java.util.EnumSet} and {@link java.util.EnumMap}.
*
* @return the ordinal of this enumeration constant
*/publicfinalintordinal(){returnordinal;}/**
* 唯一的构造函数，程序员无法调用次构造函数。它由编译器在进行枚举类型声明时调用。
*
* @param name - The name of this enum constant, which is the identifier
* used to declare it.
* @param ordinal - The ordinal of this enumeration constant (its position
* in the enum declaration, where the initial constant is assigned
* an ordinal of zero).
*/protectedEnum(Stringname,intordinal){this.name=name;this.ordinal=ordinal;}/**
* Returns the name of this enum constant, as contained in the
* declaration. This method may be overridden, though it typically
* isn't necessary or desirable. An enum type should override this
* method when a more "programmer-friendly" string form exists.
*
* @return the name of this enum constant
*/publicStringtoString(){returnname;}/**
* Returns true if the specified object is equal to this
* enum constant.
*
* @param other the object to be compared for equality with this object.
* @return true if the specified object is equal to this
* enum constant.
*/publicfinalbooleanequals(Objectother){returnthis==other;}/**
* Returns a hash code for this enum constant.
*
* @return a hash code for this enum constant.
*/publicfinalinthashCode(){returnsuper.hashCode();}/**
* 抛出CloneNotSupportedException。这保证了枚举永远不会被克隆，这保证它们的“单例状态”。
*
* @return (never returns)
*/protectedfinalObjectclone()throwsCloneNotSupportedException{thrownewCloneNotSupportedException();}/**
* Compares this enum with the specified object for order. Returns a
* negative integer, zero, or a positive integer as this object is less
* than, equal to, or greater than the specified object.
*
* Enum constants are only comparable to other enum constants of the
* same enum type. The natural order implemented by this
* method is the order in which the constants are declared.
*/publicfinalintcompareTo(Eo){Enum<?>other=(Enum<?>)o;Enum<E>self=this;if(self.getClass()!=other.getClass()&&// optimization
self.getDeclaringClass()!=other.getDeclaringClass())thrownewClassCastException();returnself.ordinal-other.ordinal;}/**
* Returns the Class object corresponding to this enum constant's
* enum type. Two enum constants e1 and e2 are of the
* same enum type if and only if
* e1.getDeclaringClass() == e2.getDeclaringClass().
* (The value returned by this method may differ from the one returned
* by the {@link Object#getClass} method for enum constants with
* constant-specific class bodies.)
*
* @return the Class object corresponding to this enum constant's
* enum type
*/@SuppressWarnings("unchecked")publicfinalClass<E>getDeclaringClass(){Class<?>clazz=getClass();Class<?>zuper=clazz.getSuperclass();return(zuper==Enum.class)?(Class<E>)clazz:(Class<E>)zuper;}/**
* 返回指定枚举类型和名称的枚举常量，名称必须与声明的完全匹配。
* 无关的空白字符是不被允许的。
* <p>Note that for a particular enum type {@code T}, the
* implicitly declared {@code public static T valueOf(String)}
* method on that enum may be used instead of this method to map
* from a name to the corresponding enum constant. 所有的枚举常量值可以通过调用隐式方法{@code public static T[] values()}获得。
*
* @param <T> The enum type whose constant is to be returned
* @param enumType the {@code Class} object of the enum type from which
* to return a constant
* @param name the name of the constant to return
* @return the enum constant of the specified enum type with the
* specified name
* @throws IllegalArgumentException if the specified enum type has
* no constant with the specified name, or the specified
* class object does not represent an enum type
* @throws NullPointerException if {@code enumType} or {@code name}
* is null
* @since 1.5
*/publicstatic<TextendsEnum<T>>TvalueOf(Class<T>enumType,Stringname){Tresult=enumType.enumConstantDirectory().get(name);if(result!=null)returnresult;if(name==null)thrownewNullPointerException("Name is null");thrownewIllegalArgumentException("No enum constant "+enumType.getCanonicalName()+"."+name);}/**
* enum classes cannot have finalize methods.
*/protectedfinalvoidfinalize(){}/**
* 防止默认反序列化。
*/privatevoidreadObject(ObjectInputStreamin)throwsIOException,ClassNotFoundException{thrownewInvalidObjectException("can't deserialize enum");}privatevoidreadObjectNoData()throwsObjectStreamException{thrownewInvalidObjectException("can't deserialize enum");}}
