Enum
public
abstract
class
Enum
extends Object
implements
Comparable<E extends Enum<E>>,
Serializable
| java.lang.Object | |
| ↳ | java.lang.Enum<E extends java.lang.Enum<E>> |
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 {@jls 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 also:
Summary
Protected constructors | |
|---|---|
Enum(String name, int ordinal)
Sole constructor. |
|
Public methods | |
|---|---|
final
int
|
compareTo(E o)
Compares this enum with the specified object for order. |
final
boolean
|
equals(Object other)
Returns true if the specified object is equal to this enum constant. |
final
Class<E>
|
getDeclaringClass()
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). |
String
|
toString()
Returns the name of this enum constant, as contained in the declaration. |
static
<T extends Enum<T>>
T
|
valueOf(Class<T> enumClass, String name)
Returns the enum constant of the specified enum class with the specified name. |
Protected methods | |
|---|---|
final
Object
|
clone()
Throws CloneNotSupportedException. |
final
void
|
finalize()
enum classes cannot have finalize methods. |
Inherited methods | |
|---|---|
Protected constructors
Enum
protected Enum (String name, int ordinal)
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 |
String: - The name of this enum constant, which is the identifier
used to declare it. |
ordinal |
int: - The ordinal of this enumeration constant (its position
in the enum declaration, where the initial constant is assigned
an ordinal of zero). |
Public methods
compareTo
public final int compareTo (E 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.
| Parameters | |
|---|---|
o |
E |
| Returns | |
|---|---|
int |
|
equals
public final boolean equals (Object other)
Returns true if the specified object is equal to this enum constant.
| Parameters | |
|---|---|
other |
Object: the object to be compared for equality with this object. |
| Returns | |
|---|---|
boolean |
true if the specified object is equal to this enum constant. |
getDeclaringClass
public final Class<E> 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 method for enum constants with
constant-specific class bodies.)
| Returns | |
|---|---|
Class<E> |
the Class object corresponding to this enum constant's enum type |
hashCode
public final int hashCode ()
Returns a hash code for this enum constant.
| Returns | |
|---|---|
int |
a hash code for this enum constant. |
name
public final String name ()
Returns the name of this enum constant, exactly as declared in its
enum declaration.
Most programmers should use the 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 | |
|---|---|
String |
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 and EnumMap.
| Returns | |
|---|---|
int |
the ordinal of this enumeration constant |
toString
public String 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.
| Returns | |
|---|---|
String |
the name of this enum constant |
valueOf
public static T valueOf (Class<T> enumClass, String name)
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 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 class can be obtained by calling the
implicit public static T[] values() method of that
class.
| Parameters | |
|---|---|
enumClass |
Class: the Class object of the enum class from which
to return a constant |
name |
String: the name of the constant to return |
| Returns | |
|---|---|
T |
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 class |
NullPointerException |
if enumClass or name
is null |
Protected methods
clone
protected final Object clone ()
Throws CloneNotSupportedException. This guarantees that enums are never cloned, which is necessary to preserve their "singleton" status.
| Returns | |
|---|---|
Object |
(never returns) |
| Throws | |
|---|---|
CloneNotSupportedException |
|
finalize
protected final void finalize ()
enum classes cannot have finalize methods.