content: /*
   * Copyright (C) 2014 The Android Open Source Project
   * Copyright (c) 2003, 2011, 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.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.util.Objects;
  import libcore.util.BasicLruCache;
  import libcore.util.EmptyArray;
  
  /**
   * 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
   * @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
       */
      // BEGIN Android-changed: Use a static BasicLruCache mapping Enum class -> Enum instance array.
      // This change was made to fix a performance regression. See b/4087759 and b/109791362 for more
      // background information.
      public static <T extends Enum<T>> T valueOf(Class<T> enumType,
                                                  String name) {
          Objects.requireNonNull(enumType, "enumType == null");
          Objects.requireNonNull(enumType, "name == null");
          T[] values = getSharedConstants(enumType);
          if (values == null) {
              throw new IllegalArgumentException(enumType.toString() + " is not an enum type.");
          }
  
          // Iterate backwards through the array to retain historic Android behavior in the
          // unexpected / likely invalid case where there are multiple values with the same name.
          for (int i = values.length - 1; i >= 0; --i) {
              T value = values[i];
              if (name.equals(value.name())) {
                  return value;
              }
          }
          throw new IllegalArgumentException(
                  "No enum constant " + enumType.getCanonicalName() + "." + name);
      }
  
      private static Object[] enumValues(Class<? extends Enum> clazz) {
          if (!clazz.isEnum()) {
              // Either clazz is Enum.class itself, or it is not an enum class and the method was
              // called unsafely e.g. using an unchecked cast or via reflection.
              return null;
          }
          try {
              Method valueMethod = clazz.getDeclaredMethod("values");
              return (Object[]) valueMethod.invoke(null);
          } catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
              throw new RuntimeException(e);
          }
      }
  
      private static final BasicLruCache<Class<? extends Enum>, Object[]> sharedConstantsCache
              = new BasicLruCache<Class<? extends Enum>, Object[]>(64) {
          @Override protected Object[] create(Class<? extends Enum> enumType) {
              return enumValues(enumType);
          }
      };
  
      /**
       * Returns a shared, mutable array containing the constants of this enum. It
       * is an error to modify the returned array.
       *
       * @hide
       */
      @SuppressWarnings("unchecked") // the cache always returns the type matching enumType
      public static <T extends Enum<T>> T[] getSharedConstants(Class<T> enumType) {
          return (T[]) sharedConstantsCache.get(enumType);
      }
      // END Android-changed: Use a static BasicLruCache mapping Enum class -> Enum instance array.
  
      /**
       * 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");
      }
  }
  