EnumSet JDK 1.6)

java.util. EnumSet View Source

Author(s)

Josh Bloch

Since

1.5

Version

1.15, 07/10/06

Serial

exclude

Hierarchy

Object

AbstractCollection

AbstractSet

EnumSet

Implements

Cloneable

Serializable

Subclasses

Quick Links: Constructors Methods Fields NestedClasses

Description

publicabstract abstract class EnumSet

A specialized Set implementation for use with enum types.

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.

See also: EnumMap

Constructors

pack-private EnumSet (Class< E> elementType, Enum universe)

Methods

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public boolean add ( E e) [Inherited From AbstractCollection]

Ensures that this collection contains the specified element (optional operation).

pack-privateabstract void addAll ()

Adds all of the elements from the appropriate enum type to this enum set, which is empty prior to the call.

public boolean addAll (Collection<Object> c) [Inherited From AbstractCollection]

Adds all of the elements in the specified collection to this collection (optional operation).

pack-privateabstract void addRange ( E from, E to)

Adds the specified range to this enum set, which is empty prior to the call.

publicstatic EnumSet< E> allOf (Class< E> elementType)

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

public void clear () [Inherited From AbstractCollection]

Removes all of the elements from this collection (optional operation).

public EnumSet< E> clone ()

Returns a copy of this set.

pack-privateabstract void complement ()

Complements the contents of this enum set.

publicstatic 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.

public boolean contains (Object o) [Inherited From AbstractCollection]

Returns true if this collection contains the specified element.

public boolean containsAll (Collection<Object> c) [Inherited From AbstractCollection]

Returns true if this collection contains all of the elements in the specified collection.

publicstatic EnumSet< E> copyOf (Collection< E> c)

Creates an enum set initialized from the specified collection.

publicstatic 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).

public boolean equals (Object o) [Inherited From AbstractSet]

Compares the specified object with this set for equality.

public int hashCode () [Inherited From AbstractSet]

Returns the hash code value for this set.

public boolean isEmpty () [Inherited From AbstractCollection]

Returns true if this collection contains no elements.

publicabstract Iterator< E> iterator () [Inherited From AbstractCollection]

Returns an iterator over the elements contained in this collection.

publicstatic EnumSet< E> noneOf (Class< E> elementType)

Creates an empty enum set with the specified element type.

publicstatic EnumSet< E> of ( E e)

Creates an enum set initially containing the specified element.

publicstatic EnumSet< E> of ( E first, E rest)

Creates an enum set initially containing the specified elements.

publicstatic EnumSet< E> of ( E e1, E e2)

Creates an enum set initially containing the specified elements.

publicstatic EnumSet< E> of ( E e1, E e2, E e3)

Creates an enum set initially containing the specified elements.

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

Creates an enum set initially containing the specified elements.

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

Creates an enum set initially containing the specified elements.

publicstatic 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.

public boolean remove (Object o) [Inherited From AbstractCollection]

Removes a single instance of the specified element from this collection, if it is present (optional operation).

public boolean removeAll (Collection<Object> c) [Inherited From AbstractSet]

Removes from this set all of its elements that are contained in the specified collection (optional operation).

public boolean retainAll (Collection<Object> c) [Inherited From AbstractCollection]

Retains only the elements in this collection that are contained in the specified collection (optional operation).

publicabstract int size () [Inherited From AbstractCollection]

public Object toArray () [Inherited From AbstractCollection]

Returns an array containing all of the elements in this collection.

Returns an array containing all of the elements in this collection. If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.

The returned array will be "safe" in that no references to it are maintained by this collection. (In other words, this method must allocate a new array even if this collection is backed by an array). The caller is thus free to modify the returned array.

This method acts as bridge between array-based and collection-based APIs.

This implementation returns an array containing all the elements returned by this collection's iterator, in the same order, stored in consecutive elements of the array, starting with index 0. The length of the returned array is equal to the number of elements returned by the iterator, even if the size of this collection changes during iteration, as might happen if the collection permits concurrent modification during iteration. The size method is called only as an optimization hint; the correct result is returned even if the iterator returns a different number of elements.

This method is equivalent to:

 List<E> list = new ArrayList<E>(size());
 for (E e : this)
     list.add(e);
 return list.toArray();

public T toArray ( T a) [Inherited From AbstractCollection]

Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.

Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. If the collection fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this collection.

If this collection fits in the specified array with room to spare (i.e., the array has more elements than this collection), the element in the array immediately following the end of the collection is set to null. (This is useful in determining the length of this collection only if the caller knows that this collection does not contain any null elements.)

If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.

Like the Collection.toArray() method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs.

Suppose x is a collection known to contain only strings. The following code can be used to dump the collection into a newly allocated array of String:

     String[] y = x.toArray(new String[0]);

Note that toArray(new Object[0]) is identical in function to toArray().

This implementation returns an array containing all the elements returned by this collection's iterator in the same order, stored in consecutive elements of the array, starting with index 0. If the number of elements returned by the iterator is too large to fit into the specified array, then the elements are returned in a newly allocated array with length equal to the number of elements returned by the iterator, even if the size of this collection changes during iteration, as might happen if the collection permits concurrent modification during iteration. The size method is called only as an optimization hint; the correct result is returned even if the iterator returns a different number of elements.

This method is equivalent to:

 List<E> list = new ArrayList<E>(size());
 for (E e : this)
     list.add(e);
 return list.toArray(a);

Throws:
- ArrayStoreException - {@inheritDoc}
- NullPointerException - {@inheritDoc}

public String toString () [Inherited From AbstractCollection]

Returns a string representation of this collection.

pack-privatefinal void typeCheck ( E e)

Throws an exception if e is not of the correct type for this enum set.

pack-private Object writeReplace ()

Fields

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pack-privatefinal Class< E> elementType

The class of all the elements of this set.

pack-privatefinal Enum universe

All of the values comprising T.

Nested Classes