52  *
  53  * <P>Like most collection implementations, {@code EnumSet} is not
  54  * synchronized.  If multiple threads access an enum set concurrently, and at
  55  * least one of the threads modifies the set, it should be synchronized
  56  * externally.  This is typically accomplished by synchronizing on some
  57  * object that naturally encapsulates the enum set.  If no such object exists,
  58  * the set should be "wrapped" using the {@link Collections#synchronizedSet}
  59  * method.  This is best done at creation time, to prevent accidental
  60  * unsynchronized access:
  61  *
  62  * <pre>
  63  * Set&lt;MyEnum&gt; s = Collections.synchronizedSet(EnumSet.noneOf(MyEnum.class));
  64  * </pre>
  65  *
  66  * <p>Implementation note: All basic operations execute in constant time.
  67  * They are likely (though not guaranteed) to be much faster than their
  68  * {@link HashSet} counterparts.  Even bulk operations execute in
  69  * constant time if their argument is also an enum set.
  70  *
  71  * <p>This class is a member of the
  72  * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
  73  * Java Collections Framework</a>.
  74  *
  75  * @author Josh Bloch
  76  * @since 1.5
  77  * @see EnumMap
  78  */
  79 @SuppressWarnings("serial") // No serialVersionUID due to usage of
  80                             // serial proxy pattern
  81 public abstract class EnumSet<E extends Enum<E>> extends AbstractSet<E>
  82     implements Cloneable, java.io.Serializable
  83 {
  84     /**
  85      * The class of all the elements of this set.
  86      */
  87     final transient Class<E> elementType;
  88 
  89     /**
  90      * All of the values comprising E.  (Cached for performance.)
  91      */
  92     final transient Enum<?>[] universe;

  52  *
  53  * <P>Like most collection implementations, {@code EnumSet} is not
  54  * synchronized.  If multiple threads access an enum set concurrently, and at
  55  * least one of the threads modifies the set, it should be synchronized
  56  * externally.  This is typically accomplished by synchronizing on some
  57  * object that naturally encapsulates the enum set.  If no such object exists,
  58  * the set should be "wrapped" using the {@link Collections#synchronizedSet}
  59  * method.  This is best done at creation time, to prevent accidental
  60  * unsynchronized access:
  61  *
  62  * <pre>
  63  * Set&lt;MyEnum&gt; s = Collections.synchronizedSet(EnumSet.noneOf(MyEnum.class));
  64  * </pre>
  65  *
  66  * <p>Implementation note: All basic operations execute in constant time.
  67  * They are likely (though not guaranteed) to be much faster than their
  68  * {@link HashSet} counterparts.  Even bulk operations execute in
  69  * constant time if their argument is also an enum set.
  70  *
  71  * <p>This class is a member of the
  72  * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
  73  * Java Collections Framework</a>.
  74  *
  75  * @author Josh Bloch
  76  * @since 1.5
  77  * @see EnumMap
  78  */
  79 @SuppressWarnings("serial") // No serialVersionUID due to usage of
  80                             // serial proxy pattern
  81 public abstract class EnumSet<E extends Enum<E>> extends AbstractSet<E>
  82     implements Cloneable, java.io.Serializable
  83 {
  84     /**
  85      * The class of all the elements of this set.
  86      */
  87     final transient Class<E> elementType;
  88 
  89     /**
  90      * All of the values comprising E.  (Cached for performance.)
  91      */
  92     final transient Enum<?>[] universe;