Java™ Platform
Standard Ed. 6

java.util
Class EnumSet<E extends Enum<E>>

java.lang.Object
  extended by java.util.AbstractCollection<E>
      extended by java.util.AbstractSet<E>
          extended by java.util.EnumSet<E>
All Implemented Interfaces:
Serializable, Cloneable, Iterable<E>, Collection<E>, Set<E>

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

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(java.util.Set) 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.

Since:
1.5
See Also:
EnumMap

Method Summary
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(Collection<E> c)
          Creates an enum set initialized from the specified collection.
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>
noneOf(Class<E> elementType)
          Creates an empty enum set with the specified element type.
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>
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)
          Creates an enum set initially containing the specified elements.
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, E e3, E e4)
          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>
range(E from, E to)
          Creates an enum set initially containing all of the elements in the range defined by the two specified endpoints.
 
Methods inherited from class java.util.AbstractSet
equals, hashCode, removeAll
 
Methods inherited from class java.util.AbstractCollection
add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, retainAll, size, toArray, toArray, toString
 
Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface java.util.Set
add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, retainAll, size, toArray, toArray
 

Method Detail

noneOf

public static <E extends Enum<E>> EnumSet<E> noneOf(Class<E> elementType)
Creates an empty enum set with the specified element type.

Parameters:
elementType - the class object of the element type for this enum set
Throws:
NullPointerException - if elementType is null

allOf

public 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.

Parameters:
elementType - the class object of the element type for this enum set
Throws:
NullPointerException - if elementType is null

copyOf

public 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).

Parameters:
s - the enum set from which to initialize this enum set
Throws:
NullPointerException - if s is null

copyOf

public static <E extends Enum<E>> 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(EnumSet). Otherwise, the specified collection must contain at least one element (in order to determine the new enum set's element type).

Parameters:
c - the collection from which to initialize this enum set
Throws:
IllegalArgumentException - if c is not an EnumSet instance and contains no elements
NullPointerException - if c is null

complementOf

public 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.

Parameters:
s - the enum set from whose complement to initialize this enum set
Throws:
NullPointerException - if s is null

of

public static <E extends Enum<E>> 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 - the element that this set is to contain initially
Returns:
an enum set initially containing the specified element
Throws:
NullPointerException - if e is null

of

public static <E extends Enum<E>> 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 - an element that this set is to contain initially
e2 - another element that this set is to contain initially
Returns:
an enum set initially containing the specified elements
Throws:
NullPointerException - if any parameters are null

of

public static <E extends Enum<E>> 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 - an element that this set is to contain initially
e2 - another element that this set is to contain initially
e3 - another element that this set is to contain initially
Returns:
an enum set initially containing the specified elements
Throws:
NullPointerException - if any parameters are null

of

public 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. 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 - an element that this set is to contain initially
e2 - another element that this set is to contain initially
e3 - another element that this set is to contain initially
e4 - another element that this set is to contain initially
Returns:
an enum set initially containing the specified elements
Throws:
NullPointerException - if any parameters are null

of

public 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. 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 - an element that this set is to contain initially
e2 - another element that this set is to contain initially
e3 - another element that this set is to contain initially
e4 - another element that this set is to contain initially
e5 - another element that this set is to contain initially
Returns:
an enum set initially containing the specified elements
Throws:
NullPointerException - if any parameters are null

of

public static <E extends Enum<E>> 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 - an element that the set is to contain initially
rest - the remaining elements the set is to contain initially
Returns:
an enum set initially containing the specified elements
Throws:
NullPointerException - if any of the specified elements are null, or if rest is null

range

public 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. The returned set will contain the endpoints themselves, which may be identical but must not be out of order.

Parameters:
from - the first element in the range
to - the last element in the range
Returns:
an enum set initially containing all of the elements in the range defined by the two specified endpoints
Throws:
NullPointerException - if first or last are null
IllegalArgumentException - if first.compareTo(last) > 0

clone

public EnumSet<E> clone()
Returns a copy of this set.

Overrides:
clone in class Object
Returns:
a copy of this set
See Also:
Cloneable

Java™ Platform
Standard Ed. 6

Submit a bug or feature
For further API reference and developer documentation, see Java SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright © 1993, 2011, Oracle and/or its affiliates. All rights reserved.

Scripting on this page tracks web page traffic, but does not change the content in any way.