Added in API level 1

Summary: Methods | Inherited Methods

EnumSet

public abstract class EnumSet
extends AbstractSet<E extends Enum<E>> implements Cloneable, Serializable

java.lang.Object
↳	java.util.AbstractCollection<E extends java.lang.Enum<E>>
	↳	java.util.AbstractSet<E extends java.lang.Enum<E>>
		↳	java.util.EnumSet<E extends java.lang.Enum<E>>

---

A specialized Set implementation for use with enum types. All of the elements in an enum set must come from a single enum type that is specified, explicitly or implicitly, when the set is created. Enum sets are represented internally as bit vectors. This representation is extremely compact and efficient. The space and time performance of this class should be good enough to allow its use as a high-quality, typesafe alternative to traditional int-based "bit flags." Even bulk operations (such as containsAll and retainAll) should run very quickly if their argument is also an enum set.

The iterator returned by the iterator method traverses the elements in their natural order (the order in which the enum constants are declared). The returned iterator is weakly consistent: it will never throw ConcurrentModificationException and it may or may not show the effects of any modifications to the set that occur while the iteration is in progress.

Null elements are not permitted. Attempts to insert a null element will throw NullPointerException. Attempts to test for the presence of a null element or to remove one will, however, function properly.

Like most collection implementations, EnumSet is not synchronized. If multiple threads access an enum set concurrently, and at least one of the threads modifies the set, it should be synchronized externally. This is typically accomplished by synchronizing on some object that naturally encapsulates the enum set. If no such object exists, the set should be "wrapped" using the Collections.synchronizedSet method. This is best done at creation time, to prevent accidental unsynchronized access:

 Set<MyEnum> s = Collections.synchronizedSet(EnumSet.noneOf(MyEnum.class));
 

Implementation note: All basic operations execute in constant time. They are likely (though not guaranteed) to be much faster than their HashSet counterparts. Even bulk operations execute in constant time if their argument is also an enum set.

This class is a member of the Java Collections Framework.

See also:

• EnumMap

Summary

Public methods
static <E extends Enum<E>> EnumSet<E>	allOf(Class<E> elementType) Creates an enum set containing all of the elements in the specified element type.
EnumSet<E>	clone() Returns a copy of this set.
static <E extends Enum<E>> EnumSet<E>	complementOf(EnumSet<E> s) Creates an enum set with the same element type as the specified enum set, initially containing all the elements of this type that are not contained in the specified set.
static <E extends Enum<E>> EnumSet<E>	copyOf(EnumSet<E> s) Creates an enum set with the same element type as the specified enum set, initially containing the same elements (if any).
static <E extends Enum<E>> EnumSet<E>	copyOf(Collection<E> c) Creates an enum set initialized from the specified collection.
static <E extends Enum<E>> EnumSet<E>	noneOf(Class<E> elementType) Creates an empty enum set with the specified element type.
static <E extends Enum<E>> EnumSet<E>	of(E e1, E e2, E e3) Creates an enum set initially containing the specified elements.
static <E extends Enum<E>> EnumSet<E>	of(E e1, E e2) Creates an enum set initially containing the specified elements.
static <E extends Enum<E>> EnumSet<E>	of(E e1, E e2, E e3, E e4, E e5) Creates an enum set initially containing the specified elements.
static <E extends Enum<E>> EnumSet<E>	of(E first, E... rest) Creates an enum set initially containing the specified elements.
static <E extends Enum<E>> EnumSet<E>	of(E e1, E e2, E e3, E e4) Creates an enum set initially containing the specified elements.
static <E extends Enum<E>> EnumSet<E>	of(E e) Creates an enum set initially containing the specified element.
static <E extends Enum<E>> EnumSet<E>	range(E from, E to) Creates an enum set initially containing all of the elements in the range defined by the two specified endpoints.

Inherited methods
From class java.util.AbstractSet boolean equals(Object o) Compares the specified object with this set for equality. int hashCode() Returns the hash code value for this set. boolean removeAll(Collection<?> c) Removes from this set all of its elements that are contained in the specified collection (optional operation).
From class java.util.AbstractCollection boolean add(E e) Ensures that this collection contains the specified element (optional operation). boolean addAll(Collection<? extends E> c) Adds all of the elements in the specified collection to this collection (optional operation). void clear() Removes all of the elements from this collection (optional operation). boolean contains(Object o) Returns true if this collection contains the specified element. boolean containsAll(Collection<?> c) Returns true if this collection contains all of the elements in the specified collection. boolean isEmpty() Returns true if this collection contains no elements. abstract Iterator<E> iterator() Returns an iterator over the elements contained in this collection. boolean remove(Object o) Removes a single instance of the specified element from this collection, if it is present (optional operation). boolean removeAll(Collection<?> c) Removes all of this collection's elements that are also contained in the specified collection (optional operation). boolean retainAll(Collection<?> c) Retains only the elements in this collection that are contained in the specified collection (optional operation). abstract int size() Returns the number of elements in this collection. <T> T[] toArray(T[] a) Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. Object[] toArray() Returns an array containing all of the elements in this collection. String toString() Returns a string representation of this collection.
From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. final Class<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
From interface java.util.Set abstract boolean add(E e) Adds the specified element to this set if it is not already present (optional operation). abstract boolean addAll(Collection<? extends E> c) Adds all of the elements in the specified collection to this set if they're not already present (optional operation). abstract void clear() Removes all of the elements from this set (optional operation). abstract boolean contains(Object o) Returns true if this set contains the specified element. abstract boolean containsAll(Collection<?> c) Returns true if this set contains all of the elements of the specified collection. static <E> Set<E> copyOf(Collection<? extends E> coll) Returns an unmodifiable Set containing the elements of the given Collection. abstract boolean equals(Object o) Compares the specified object with this set for equality. abstract int hashCode() Returns the hash code value for this set. abstract boolean isEmpty() Returns true if this set contains no elements. abstract Iterator<E> iterator() Returns an iterator over the elements in this set. static <E> Set<E> of(E e1, E e2, E e3) Returns an unmodifiable set containing three elements. static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) Returns an unmodifiable set containing nine elements. static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5) Returns an unmodifiable set containing five elements. static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6) Returns an unmodifiable set containing six elements. static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) Returns an unmodifiable set containing eight elements. static <E> Set<E> of(E... elements) Returns an unmodifiable set containing an arbitrary number of elements. static <E> Set<E> of() Returns an unmodifiable set containing zero elements. static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10) Returns an unmodifiable set containing ten elements. static <E> Set<E> of(E e1, E e2) Returns an unmodifiable set containing two elements. static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7) Returns an unmodifiable set containing seven elements. static <E> Set<E> of(E e1, E e2, E e3, E e4) Returns an unmodifiable set containing four elements. static <E> Set<E> of(E e1) Returns an unmodifiable set containing one element. abstract boolean remove(Object o) Removes the specified element from this set if it is present (optional operation). abstract boolean removeAll(Collection<?> c) Removes from this set all of its elements that are contained in the specified collection (optional operation). abstract boolean retainAll(Collection<?> c) Retains only the elements in this set that are contained in the specified collection (optional operation). abstract int size() Returns the number of elements in this set (its cardinality). default Spliterator<E> spliterator() Creates a Spliterator over the elements in this set. abstract Object[] toArray() Returns an array containing all of the elements in this set. abstract <T> T[] toArray(T[] a) Returns an array containing all of the elements in this set; the runtime type of the returned array is that of the specified array.
From interface java.util.Collection abstract boolean add(E e) Ensures that this collection contains the specified element (optional operation). abstract boolean addAll(Collection<? extends E> c) Adds all of the elements in the specified collection to this collection (optional operation). abstract void clear() Removes all of the elements from this collection (optional operation). abstract boolean contains(Object o) Returns true if this collection contains the specified element. abstract boolean containsAll(Collection<?> c) Returns true if this collection contains all of the elements in the specified collection. abstract boolean equals(Object o) Compares the specified object with this collection for equality. abstract int hashCode() Returns the hash code value for this collection. abstract boolean isEmpty() Returns true if this collection contains no elements. abstract Iterator<E> iterator() Returns an iterator over the elements in this collection. default Stream<E> parallelStream() Returns a possibly parallel Stream with this collection as its source. abstract boolean remove(Object o) Removes a single instance of the specified element from this collection, if it is present (optional operation). abstract boolean removeAll(Collection<?> c) Removes all of this collection's elements that are also contained in the specified collection (optional operation). default boolean removeIf(Predicate<? super E> filter) Removes all of the elements of this collection that satisfy the given predicate. abstract boolean retainAll(Collection<?> c) Retains only the elements in this collection that are contained in the specified collection (optional operation). abstract int size() Returns the number of elements in this collection. default Spliterator<E> spliterator() Creates a Spliterator over the elements in this collection. default Stream<E> stream() Returns a sequential Stream with this collection as its source. abstract <T> T[] toArray(T[] a) Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. abstract Object[] toArray() Returns an array containing all of the elements in this collection. default <T> T[] toArray(IntFunction<T[]> generator) Returns an array containing all of the elements in this collection, using the provided generator function to allocate the returned array.
From interface java.lang.Iterable default void forEach(Consumer<? super T> action) Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception. abstract Iterator<E extends Enum<E>> iterator() Returns an iterator over elements of type T. default Spliterator<E extends Enum<E>> spliterator() Creates a Spliterator over the elements described by this Iterable.

Public methods

allOf

Added in API level 1

public static EnumSet<E> allOf (Class<E> elementType)

Creates an enum set containing all of the elements in the specified element type.

Parameters
elementType	Class: the class object of the element type for this enum set

Returns
EnumSet<E>	An enum set containing all the elements in the specified type.

Throws
NullPointerException	if elementType is null

clone

Added in API level 1

public EnumSet<E> clone ()

Returns a copy of this set.

Returns
EnumSet<E>	a copy of this set

complementOf

Added in API level 1

public static EnumSet<E> complementOf (EnumSet<E> s)

Creates an enum set with the same element type as the specified enum set, initially containing all the elements of this type that are not contained in the specified set.

Parameters
s	EnumSet: the enum set from whose complement to initialize this enum set

Returns
EnumSet<E>	The complement of the specified set in this set

Throws
NullPointerException	if s is null

copyOf

Added in API level 1

public static EnumSet<E> copyOf (EnumSet<E> s)

Creates an enum set with the same element type as the specified enum set, initially containing the same elements (if any).

Parameters
s	EnumSet: the enum set from which to initialize this enum set

Returns
EnumSet<E>	A copy of the specified enum set.

Throws
NullPointerException	if s is null

copyOf

Added in API level 1

public static EnumSet<E> copyOf (Collection<E> c)

Creates an enum set initialized from the specified collection. If the specified collection is an EnumSet instance, this static factory method behaves identically to copyOf(java.util.EnumSet). Otherwise, the specified collection must contain at least one element (in order to determine the new enum set's element type).

Parameters
c	Collection: the collection from which to initialize this enum set

Returns
EnumSet<E>	An enum set initialized from the given collection.

Throws
IllegalArgumentException	if c is not an EnumSet instance and contains no elements
NullPointerException	if c is null

noneOf

Added in API level 1

public static EnumSet<E> noneOf (Class<E> elementType)

Creates an empty enum set with the specified element type.

Parameters
elementType	Class: the class object of the element type for this enum set

Returns
EnumSet<E>	An empty enum set of the specified type.

Throws
NullPointerException	if elementType is null

of

Added in API level 1

public static EnumSet<E> of (E e1, 
                E e2, 
                E e3)

Creates an enum set initially containing the specified elements. Overloadings of this method exist to initialize an enum set with one through five elements. A sixth overloading is provided that uses the varargs feature. This overloading may be used to create an enum set initially containing an arbitrary number of elements, but is likely to run slower than the overloadings that do not use varargs.

Parameters
e1	E: an element that this set is to contain initially
e2	E: another element that this set is to contain initially
e3	E: another element that this set is to contain initially

Returns
EnumSet<E>	an enum set initially containing the specified elements

Throws
NullPointerException	if any parameters are null

of

Added in API level 1

public static EnumSet<E> of (E e1, 
                E e2)

Creates an enum set initially containing the specified elements. Overloadings of this method exist to initialize an enum set with one through five elements. A sixth overloading is provided that uses the varargs feature. This overloading may be used to create an enum set initially containing an arbitrary number of elements, but is likely to run slower than the overloadings that do not use varargs.

Parameters
e1	E: an element that this set is to contain initially
e2	E: another element that this set is to contain initially

Returns
EnumSet<E>	an enum set initially containing the specified elements

Throws
NullPointerException	if any parameters are null

of

Added in API level 1

public static EnumSet<E> of (E e1, 
                E e2, 
                E e3, 
                E e4, 
                E e5)

Creates an enum set initially containing the specified elements. Overloadings of this method exist to initialize an enum set with one through five elements. A sixth overloading is provided that uses the varargs feature. This overloading may be used to create an enum set initially containing an arbitrary number of elements, but is likely to run slower than the overloadings that do not use varargs.

Parameters
e1	E: an element that this set is to contain initially
e2	E: another element that this set is to contain initially
e3	E: another element that this set is to contain initially
e4	E: another element that this set is to contain initially
e5	E: another element that this set is to contain initially

Returns
EnumSet<E>	an enum set initially containing the specified elements

Throws
NullPointerException	if any parameters are null

of

Added in API level 1

public static EnumSet<E> of (E first, 
                E... rest)

Creates an enum set initially containing the specified elements. This factory, whose parameter list uses the varargs feature, may be used to create an enum set initially containing an arbitrary number of elements, but it is likely to run slower than the overloadings that do not use varargs.

Parameters
first	E: an element that the set is to contain initially
rest	E: the remaining elements the set is to contain initially

Returns
EnumSet<E>	an enum set initially containing the specified elements

Throws
NullPointerException	if any of the specified elements are null, or if rest is null

of

Added in API level 1

public static EnumSet<E> of (E e1, 
                E e2, 
                E e3, 
                E e4)

Creates an enum set initially containing the specified elements. Overloadings of this method exist to initialize an enum set with one through five elements. A sixth overloading is provided that uses the varargs feature. This overloading may be used to create an enum set initially containing an arbitrary number of elements, but is likely to run slower than the overloadings that do not use varargs.

Parameters
e1	E: an element that this set is to contain initially
e2	E: another element that this set is to contain initially
e3	E: another element that this set is to contain initially
e4	E: another element that this set is to contain initially

Returns
EnumSet<E>	an enum set initially containing the specified elements

Throws
NullPointerException	if any parameters are null

of

Added in API level 1

public static EnumSet<E> of (E e)

Creates an enum set initially containing the specified element. Overloadings of this method exist to initialize an enum set with one through five elements. A sixth overloading is provided that uses the varargs feature. This overloading may be used to create an enum set initially containing an arbitrary number of elements, but is likely to run slower than the overloadings that do not use varargs.

Parameters
e	E: the element that this set is to contain initially

Returns
EnumSet<E>	an enum set initially containing the specified element

Throws
NullPointerException	if e is null

range

Added in API level 1

public static EnumSet<E> range (E from, 
                E to)

Creates an enum set initially containing all of the elements in the range defined by the two specified endpoints. The returned set will contain the endpoints themselves, which may be identical but must not be out of order.

Parameters
from	E: the first element in the range
to	E: the last element in the range

Returns
EnumSet<E>	an enum set initially containing all of the elements in the range defined by the two specified endpoints

Throws
NullPointerException	if from or to are null
IllegalArgumentException	if from.compareTo(to) > 0