Enum (Java Platform SE 8 ) (original) (raw)

• java.lang.Object

• • java.lang.Enum

• Type Parameters:
  E - The enum type subclass
  All Implemented Interfaces:
  Serializable, Comparable

public abstract class Enum<E extends Enum>
extends Object
implements Comparable, Serializable
This is the common base class of all Java language enumeration types. More information about enums, including descriptions of the implicitly declared methods synthesized by the compiler, can be found in section 8.9 ofThe Java™ Language Specification.
Note that when using an enumeration type as the type of a set or as the type of the keys in a map, specialized and efficientset and map implementations are available.
Since:
1.5
See Also:
Class.getEnumConstants(), EnumSet, EnumMap, Serialized Form

• • Constructor Summary

  Constructors

  Modifier	Constructor	Description
  protected	Enum(String name, int ordinal)	Sole constructor.

  • Method Summary

  All Methods Static Methods Instance Methods Concrete Methods

  Modifier and Type	Method	Description
  protected Object	clone()	Throws CloneNotSupportedException.
  int	compareTo(E o)	Compares this enum with the specified object for order.
  boolean	equals(Object other)	Returns true if the specified object is equal to this enum constant.
  protected void	finalize()	enum classes cannot have finalize methods.
  Class<E>	getDeclaringClass()	Returns the Class object corresponding to this enum constant's enum type.
  int	hashCode()	Returns a hash code for this enum constant.
  String	name()	Returns the name of this enum constant, exactly as declared in its enum declaration.
  int	ordinal()	Returns the ordinal of this enumeration constant (its position in its enum declaration, where the initial constant is assigned an ordinal of zero).
  String	toString()	Returns the name of this enum constant, as contained in the declaration.
  static <T extends Enum>T	valueOf(Class enumType,String name)	Returns the enum constant of the specified enum type with the specified name.

     * ### Methods inherited from class java.lang.[Object](../../java/lang/Object.html "class in java.lang")  
     `[getClass](../../java/lang/Object.html#getClass--), [notify](../../java/lang/Object.html#notify--), [notifyAll](../../java/lang/Object.html#notifyAll--), [wait](../../java/lang/Object.html#wait--), [wait](../../java/lang/Object.html#wait-long-), [wait](../../java/lang/Object.html#wait-long-int-)`

• • Constructor Detail

     * #### Enum  
     protected Enum([String](../../java/lang/String.html "class in java.lang") name,  
                    int ordinal)  
     Sole constructor. Programmers cannot invoke this constructor. It is for use by code emitted by the compiler in response to enum type declarations.  
     Parameters:  
     `name` \- - The name of this enum constant, which is the identifier used to declare it.  
     `ordinal` \- - The ordinal of this enumeration constant (its position in the enum declaration, where the initial constant is assigned an ordinal of zero).  

  • Method Detail

    * #### name  
    public final [String](../../java/lang/String.html "class in java.lang") name()  
    Returns the name of this enum constant, exactly as declared in its enum declaration.**Most programmers should use the [toString()](../../java/lang/Enum.html#toString--) method in preference to this one, as the toString method may return a more user-friendly name.** 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.  
    Returns:  
    the name of this enum constant  
    * #### ordinal  
    public final int ordinal()  
    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 [EnumSet](../../java/util/EnumSet.html "class in java.util") and [EnumMap](../../java/util/EnumMap.html "class in java.util").  
    Returns:  
    the ordinal of this enumeration constant  
    * #### toString  
    public [String](../../java/lang/String.html "class in java.lang") toString()  
    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.  
    Overrides:  
    `[toString](../../java/lang/Object.html#toString--)` in class `[Object](../../java/lang/Object.html "class in java.lang")`  
    Returns:  
    the name of this enum constant  
    * #### equals  
    public final boolean equals([Object](../../java/lang/Object.html "class in java.lang") other)  
    Returns true if the specified object is equal to this enum constant.  
    Overrides:  
    `[equals](../../java/lang/Object.html#equals-java.lang.Object-)` in class `[Object](../../java/lang/Object.html "class in java.lang")`  
    Parameters:  
    `other` \- the object to be compared for equality with this object.  
    Returns:  
    true if the specified object is equal to this enum constant.  
    See Also:  
    [Object.hashCode()](../../java/lang/Object.html#hashCode--), [HashMap](../../java/util/HashMap.html "class in java.util")  
    * #### hashCode  
    public final int hashCode()  
    Returns a hash code for this enum constant.  
    Overrides:  
    `[hashCode](../../java/lang/Object.html#hashCode--)` in class `[Object](../../java/lang/Object.html "class in java.lang")`  
    Returns:  
    a hash code for this enum constant.  
    See Also:  
    [Object.equals(java.lang.Object)](../../java/lang/Object.html#equals-java.lang.Object-), [System.identityHashCode(java.lang.Object)](../../java/lang/System.html#identityHashCode-java.lang.Object-)  
    * #### clone  
    protected final [Object](../../java/lang/Object.html "class in java.lang") clone()  
                          throws [CloneNotSupportedException](../../java/lang/CloneNotSupportedException.html "class in java.lang")  
    Throws CloneNotSupportedException. This guarantees that enums are never cloned, which is necessary to preserve their "singleton" status.  
    Overrides:  
    `[clone](../../java/lang/Object.html#clone--)` in class `[Object](../../java/lang/Object.html "class in java.lang")`  
    Returns:  
    (never returns)  
    Throws:  
    `[CloneNotSupportedException](../../java/lang/CloneNotSupportedException.html "class in java.lang")` \- if the object's class does not support the `Cloneable` interface. Subclasses that override the `clone` method can also throw this exception to indicate that an instance cannot be cloned.  
    See Also:  
    [Cloneable](../../java/lang/Cloneable.html "interface in java.lang")  
    * #### compareTo  
    public final int compareTo([E](../../java/lang/Enum.html "type parameter in Enum") o)  
    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.  
    Specified by:  
    `[compareTo](../../java/lang/Comparable.html#compareTo-T-)` in interface `[Comparable](../../java/lang/Comparable.html "interface in java.lang")<[E](../../java/lang/Enum.html "type parameter in Enum") extends [Enum](../../java/lang/Enum.html "class in java.lang")<[E](../../java/lang/Enum.html "type parameter in Enum")>>`  
    Parameters:  
    `o` \- the object to be compared.  
    Returns:  
    a negative integer, zero, or a positive integer as this object is less than, equal to, or greater than the specified object.  
    * #### getDeclaringClass  
    public final [Class](../../java/lang/Class.html "class in java.lang")<[E](../../java/lang/Enum.html "type parameter in Enum")> getDeclaringClass()  
    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 [Object.getClass()](../../java/lang/Object.html#getClass--) method for enum constants with constant-specific class bodies.)  
    Returns:  
    the Class object corresponding to this enum constant's enum type  
    * #### valueOf  
    public static <T extends [Enum](../../java/lang/Enum.html "class in java.lang")<T>> T valueOf([Class](../../java/lang/Class.html "class in java.lang")<T> enumType,  
                                                [String](../../java/lang/String.html "class in java.lang") name)  
    Returns the enum constant of the specified enum type with the specified name. The name must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)  
    Note that for a particular enum type `T`, the implicitly declared `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. All the constants of an enum type can be obtained by calling the implicit `public static T[] values()` method of that type.  
    Type Parameters:  
    `T` \- The enum type whose constant is to be returned  
    Parameters:  
    `enumType` \- the `Class` object of the enum type from which to return a constant  
    `name` \- the name of the constant to return  
    Returns:  
    the enum constant of the specified enum type with the specified name  
    Throws:  
    `[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if the specified enum type has no constant with the specified name, or the specified class object does not represent an enum type  
    `[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if `enumType` or `name` is null  
    Since:  
    1.5  
    * #### finalize  
    protected final void finalize()  
    enum classes cannot have finalize methods.  
    Overrides:  
    `[finalize](../../java/lang/Object.html#finalize--)` in class `[Object](../../java/lang/Object.html "class in java.lang")`  
    See Also:  
    [WeakReference](../../java/lang/ref/WeakReference.html "class in java.lang.ref"), [PhantomReference](../../java/lang/ref/PhantomReference.html "class in java.lang.ref")

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