/*
- * Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */
 
 package java.lang;
 
-import java.io.Serializable;
 import java.io.IOException;
 import java.io.InvalidObjectException;
 import java.io.ObjectInputStream;
 import java.io.ObjectStreamException;
+import java.io.Serializable;
+import java.lang.constant.ClassDesc;
+import java.lang.constant.Constable;
+import java.lang.constant.ConstantDescs;
+import java.lang.constant.DynamicConstantDesc;
+import java.lang.invoke.MethodHandles;
+import java.util.Optional;
+
+import static java.util.Objects.requireNonNull;
 
 /**
  * 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&trade; 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
+ * @serial exclude
  * @author  Josh Bloch
  * @author  Neal Gafter
  * @see     Class#getEnumConstants()
  * @see     java.util.EnumSet
  * @see     java.util.EnumMap
  * @since   1.5
  */
+@SuppressWarnings("serial") // No serialVersionUID needed due to
+                            // special-casing of enum types.
 public abstract class Enum<E extends Enum<E>>
-        implements Comparable<E>, Serializable {
+        implements Constable, 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 an enum descriptor {@code EnumDesc} for this instance, if one can be
+     * constructed, or an empty {@link Optional} if one cannot be.
+     *
+     * @return An {@link Optional} containing the resulting nominal descriptor,
+     * or an empty {@link Optional} if one cannot be constructed.
+     * @since 12
+     */
+    @Override
+    public final Optional<EnumDesc<E>> describeConstable() {
+        return getDeclaringClass()
+                .describeConstable()
+                .map(c -> EnumDesc.of(c, 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.)
      *
      * <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.
      */
+    @SuppressWarnings("deprecation")
     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");
     }
+
+    /**
+     * A <a href="package-summary.html#nominal">nominal descriptor</a> for an
+     * {@code enum} constant.
+     *
+     * @param <E> the type of the enum constant
+     *
+     * @since 12
+     */
+    public static final class EnumDesc<E extends Enum<E>>
+            extends DynamicConstantDesc<E> {
+
+        /**
+         * Constructs a nominal descriptor for the specified {@code enum} class and name.
+         *
+         * @param constantType a {@link ClassDesc} describing the {@code enum} class
+         * @param constantName the unqualified name of the enum constant
+         * @throws NullPointerException if any argument is null
+         * @jvms 4.2.2 Unqualified Names
+         */
+        private EnumDesc(ClassDesc constantType, String constantName) {
+            super(ConstantDescs.BSM_ENUM_CONSTANT, requireNonNull(constantName), requireNonNull(constantType));
+        }
+
+        /**
+         * Returns a nominal descriptor for the specified {@code enum} class and name
+         *
+         * @param <E> the type of the enum constant
+         * @param enumClass a {@link ClassDesc} describing the {@code enum} class
+         * @param constantName the unqualified name of the enum constant
+         * @return the nominal descriptor
+         * @throws NullPointerException if any argument is null
+         * @jvms 4.2.2 Unqualified Names
+         * @since 12
+         */
+        public static<E extends Enum<E>> EnumDesc<E> of(ClassDesc enumClass,
+                                                        String constantName) {
+            return new EnumDesc<>(enumClass, constantName);
+        }
+
+        @Override
+        @SuppressWarnings("unchecked")
+        public E resolveConstantDesc(MethodHandles.Lookup lookup)
+                throws ReflectiveOperationException {
+            return Enum.valueOf((Class<E>) constantType().resolveConstantDesc(lookup), constantName());
+        }
+
+        @Override
+        public String toString() {
+            return String.format("EnumDesc[%s.%s]", constantType().displayName(), constantName());
+        }
+    }
 }