Class Enum<E extends Enum<E>>
java.lang.Object
java.lang.Enum<E>
- Type Parameters:
E
- The type of the enum subclass
- All Implemented Interfaces:
Serializable
,Comparable<E>
,Constable
public abstract class Enum<E extends Enum<E>>
extends Object
implements Constable, Comparable<E>, Serializable
This is the common base class of all Java language enumeration classes.
More information about enums, including descriptions of the
implicitly declared methods synthesized by the compiler, can be
found in section 8.9 of The Java Language
Specification.
Enumeration classes are all serializable and receive special handling
by the serialization mechanism. The serialized representation used
for enum constants cannot be customized. Declarations of methods
and fields that would otherwise interact with serialization are
ignored, including
serialVersionUID
; see the
Java
Object Serialization Specification for details.
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 efficient set and map implementations are available.
- See Java Language Specification:
-
8.9 Enum Classes
8.9.3 Enum Members - Since:
- 1.5
- External Specifications
- See Also:
-
Nested Class Summary
Modifier and TypeClassDescriptionstatic final class
Enum.EnumDesc<E extends Enum<E>>
A nominal descriptor for anenum
constant. -
Constructor Summary
-
Method Summary
Modifier and TypeMethodDescriptionprotected final Object
clone()
Throws CloneNotSupportedException.final int
Compares this enum with the specified object for order.final Optional
<Enum.EnumDesc<E>> Returns an enum descriptorEnumDesc
for this instance, if one can be constructed, or an emptyOptional
if one cannot be.final boolean
Returns true if the specified object is equal to this enum constant.protected final void
finalize()
Deprecated, for removal: This API element is subject to removal in a future version.Finalization has been deprecated for removal.Returns the Class object corresponding to this enum constant's enum type.final int
hashCode()
Returns a hash code for this enum constant.final String
name()
Returns the name of this enum constant, exactly as declared in its enum declaration.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).toString()
Returns the name of this enum constant, as contained in the declaration.static <T extends Enum<T>>
TReturns the enum constant of the specified enum class with the specified name.
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Constructor Details
-
Enum
Sole constructor. Programmers cannot invoke this constructor. It is for use by code emitted by the compiler in response to enum class 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 Details
-
name
Returns the name of this enum constant, exactly as declared in its enum declaration. Most programmers should use thetoString()
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 asEnumSet
andEnumMap
.- Returns:
- the ordinal of this enumeration constant
-
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 class should override this method when a more "programmer-friendly" string form exists. -
equals
Returns true if the specified object is equal to this enum constant. -
hashCode
-
clone
Throws CloneNotSupportedException. This guarantees that enums are never cloned, which is necessary to preserve their "singleton" status.- Overrides:
clone
in classObject
- Returns:
- (never returns)
- Throws:
CloneNotSupportedException
- if the object's class does not support theCloneable
interface. Subclasses that override theclone
method can also throw this exception to indicate that an instance cannot be cloned.- See Also:
-
compareTo
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
in interfaceComparable<E extends Enum<E>>
- 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
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 theObject.getClass()
method for enum constants with constant-specific class bodies.)- Returns:
- the Class object corresponding to this enum constant's enum type
-
describeConstable
Returns an enum descriptorEnumDesc
for this instance, if one can be constructed, or an emptyOptional
if one cannot be.- Specified by:
describeConstable
in interfaceConstable
- Returns:
- An
Optional
containing the resulting nominal descriptor, or an emptyOptional
if one cannot be constructed. - Since:
- 12
-
valueOf
Returns the enum constant of the specified enum class with the specified name. The name must match exactly an identifier used to declare an enum constant in this class. (Extraneous whitespace characters are not permitted.)Note that for a particular enum class
T
, the implicitly declaredpublic 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 class can be obtained by calling the implicitpublic static T[] values()
method of that class.- Type Parameters:
T
- The enum class whose constant is to be returned- Parameters:
enumClass
- theClass
object of the enum class from which to return a constantname
- the name of the constant to return- Returns:
- the enum constant of the specified enum class with the specified name
- Throws:
IllegalArgumentException
- if the specified enum class has no constant with the specified name, or the specified class object does not represent an enum classNullPointerException
- ifenumClass
orname
is null- Since:
- 1.5
-
finalize
Deprecated, for removal: This API element is subject to removal in a future version.Finalization has been deprecated for removal. SeeObject.finalize()
for background information and details about migration options.enum classes cannot have finalize methods.
-