/*
* Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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package java.lang;
import java.io.
Serializable;
import java.io.
IOException;
import java.io.
InvalidObjectException;
import java.io.
ObjectInputStream;
import java.io.
ObjectStreamException;
/**
* 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 of
* <cite>The Java™ Language Specification</cite>.
*
* <p> 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
* {@linkplain java.util.EnumSet set} and {@linkplain
* java.util.EnumMap map} implementations are available.
*
* @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
*/
public abstract class
Enum<E extends
Enum<E>>
implements
Comparable<E>,
Serializable {
/**
* The name of this enum constant, as declared in the enum declaration.
* Most programmers should use the {@link #toString} method rather than
* accessing this field.
*/
private final
String name;
/**
* 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
*/
public final
String name() {
return
name;
}
/**
* The ordinal of this enumeration constant (its position
* in the enum declaration, where the initial constant is assigned
* an ordinal of zero).
*
* Most programmers will have no use for this field. It is designed
* for use by sophisticated enum-based data structures, such as
* {@link java.util.EnumSet} and {@link java.util.EnumMap}.
*/
private 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 {@link java.util.EnumSet} and {@link java.util.EnumMap}.
*
* @return the ordinal of this enumeration constant
*/
public final int
ordinal() {
return
ordinal;
}
/**
* Sole constructor. Programmers cannot invoke this constructor.
* It is for use by code emitted by the compiler in response to
* enum type declarations.
*
* @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).
*/
protected
Enum(
String name, int
ordinal) {
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
*/
public
String toString() {
return
name;
}
/**
* 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.
*/
public final boolean
equals(
Object other) {
return this==
other;
}
/**
* Returns a hash code for this enum constant.
*
* @return a hash code for this enum constant.
*/
public final int
hashCode() {
return super.hashCode();
}
/**
* Throws CloneNotSupportedException. This guarantees that enums
* are never cloned, which is necessary to preserve their "singleton"
* status.
*
* @return (never returns)
*/
protected final
Object clone() throws
CloneNotSupportedException {
throw new
CloneNotSupportedException();
}
/**
* 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.
*/
public final int
compareTo(E
o) {
Enum<?>
other = (
Enum<?>)
o;
Enum<E>
self = this;
if (
self.
getClass() !=
other.
getClass() && // optimization
self.
getDeclaringClass() !=
other.
getDeclaringClass())
throw new
ClassCastException();
return
self.
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")
public final
Class<E>
getDeclaringClass() {
Class<?>
clazz =
getClass();
Class<?>
zuper =
clazz.
getSuperclass();
return (
zuper ==
Enum.class) ? (
Class<E>)
clazz : (
Class<E>)
zuper;
}
/**
* 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.)
*
* <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. All the
* constants of an enum type can be obtained by calling the
* implicit {@code public static T[] values()} method of that
* type.
*
* @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
*/
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);
}
/**
* enum classes cannot have finalize methods.
*/
protected final void
finalize() { }
/**
* prevent default deserialization
*/
private void
readObject(
ObjectInputStream in) throws
IOException,
ClassNotFoundException {
throw new
InvalidObjectException("can't deserialize enum");
}
private void
readObjectNoData() throws
ObjectStreamException {
throw new
InvalidObjectException("can't deserialize enum");
}
}