public abstract class ImmutableSet<E> extends ImmutableCollection<E> implements Set<E>
Set
with reliable, user-specified
iteration order. Does not permit null elements.
Unlike Collections.unmodifiableSet(java.util.Set<? extends T>)
, which is a view of a
separate collection that can still change, an instance of this class contains
its own private data and will never change. This class is convenient
for public static final
sets ("constant sets") and also lets you
easily make a "defensive copy" of a set provided to your class by a caller.
Warning: Like most sets, an ImmutableSet
will not function
correctly if an element is modified after being placed in the set. For this
reason, and to avoid general confusion, it is strongly recommended to place
only immutable objects into this collection.
This class has been observed to perform significantly better than HashSet
for objects with very fast Object.hashCode()
implementations
(as a well-behaved immutable object should). While this class's factory
methods create hash-based instances, the ImmutableSortedSet
subclass
performs binary searches instead.
Note: Although this class is not final, it cannot be subclassed outside its package as it has no public or protected constructors. Thus, instances of this type are guaranteed to be immutable.
ImmutableList
,
ImmutableMap
,
Serialized FormModifier and Type | Class and Description |
---|---|
static class |
ImmutableSet.Builder<E>
A builder for creating immutable set instances, especially
public static final sets ("constant sets"). |
Modifier and Type | Method and Description |
---|---|
static <E> ImmutableSet.Builder<E> |
builder()
Returns a new builder.
|
static <E> ImmutableSet<E> |
copyOf(Iterable<? extends E> elements)
Returns an immutable set containing the given elements, in order.
|
static <E> ImmutableSet<E> |
copyOf(Iterator<? extends E> elements)
Returns an immutable set containing the given elements, in order.
|
boolean |
equals(Object object) |
int |
hashCode() |
abstract UnmodifiableIterator<E> |
iterator()
Returns an unmodifiable iterator across the elements in this collection.
|
static <E> ImmutableSet<E> |
of()
Returns the empty immutable set.
|
static <E> ImmutableSet<E> |
of(E... elements)
Returns an immutable set containing the given elements, in order.
|
static <E> ImmutableSet<E> |
of(E element)
Returns an immutable set containing a single element.
|
String |
toString() |
add, addAll, clear, contains, containsAll, isEmpty, remove, removeAll, retainAll, toArray, toArray
public static <E> ImmutableSet<E> of()
Collections.emptySet()
, and is preferable mainly for consistency
and maintainability of your code.public static <E> ImmutableSet<E> of(E element)
Collections.singleton(T)
, but will not accept
a null element. It is preferable mainly for consistency and
maintainability of your code.public static <E> ImmutableSet<E> of(E... elements)
Object.equals(java.lang.Object)
) after the
first are ignored (but too many of these may result in the set being
sized inappropriately).NullPointerException
- if any of elements
is nullpublic static <E> ImmutableSet<E> copyOf(Iterable<? extends E> elements)
Object.equals(java.lang.Object)
) after the
first are ignored (but too many of these may result in the set being
sized inappropriately). This method iterates over elements
at most
once.
Note that if s
is a Set<String>
, then ImmutableSet.copyOf(s)
returns an ImmutableSet<String>
containing
each of the strings in s
, while ImmutableSet.of(s)
returns
a ImmutableSet<Set<String>>
containing one element (the given set
itself).
Note: Despite what the method name suggests, if elements
is an ImmutableSet
(but not an ImmutableSortedSet
), no copy
will actually be performed, and the given set itself will be returned.
NullPointerException
- if any of elements
is nullpublic static <E> ImmutableSet<E> copyOf(Iterator<? extends E> elements)
Object.equals(java.lang.Object)
) after the
first are ignored.NullPointerException
- if any of elements
is nullpublic int hashCode()
public abstract UnmodifiableIterator<E> iterator()
ImmutableCollection
public String toString()
toString
in class ImmutableCollection<E>
public static <E> ImmutableSet.Builder<E> builder()
ImmutableSet.Builder
constructor.Copyright © 2006-2012 Google, Inc.. All Rights Reserved.